Five New MVL Current Mode Differential Absolute Value Circuits Based on Carbon Nano-tube Field Effect Transistors (CNTFETs)

Carbon Nano-Tube Field Effect Transistors (CNTFETs) are being widely studied as possible successors to silicon MOSFETs. Using current mode has many advantages such as performing sum operation by means of a simple wired connection. Also, direction of the current can be used to exhibit the sign of digits. It is expected that the advantages of current mode approaches will become even more important with increased speed requirements and decreased supply voltage. In this paper, we present five new circuit designs for differential absolute value in current mode logic which have been simulated by CNTFET model. The considered base current for this model is 2 µA and supply voltage is 0.9 V. In all of our designs we used N-type CNTFET current mirrors which operate as truncated difference circuits. The operation of Differential Absolute Value circuit calculates the difference between two input currents and our circuit designs are operate in 8 logic levels.

The binary logic has been used in computational circuits for many decades. But, in the recent decades Multiple-Valued Logic (MVL) is considered as an alternative to the common binary logic. MVL allows more information to be transmitted over a given set of lines results in reducing complexity of interconnections, circuitry and chip area. In this logic, arithmetic operations can be executed more efficiently and faster by increasing the radix of the systems [1][2][3][4]. MVL is a mixture design techniques of binary logic and analogue signal processing which preserves noise advantages of a digital signal while processing greater information content in analogue mode.
MVL decreases parasitic related with routing and provide a higher speed of operations. There have been many efforts to derive a reasonable MVL technology based on the voltage mode.
The most important obstruction to reception of any such technology is due to encoding more than two levels of logic in the available room temperature for voltage swing is decreased [5].
The possible approach to solve this problem is to use the current mode techniques that use current as a signal carrier, either alone or in combination with voltage. Recent experiences demonstrate that due to design simplicity and larger dynamic range, current mode approach is becoming attractive for the performing MVL function especially when the radix is larger than 3 and it can be also applied for higher radix MVL circuit design successfully [2,3,6]. Multi-valued current-mode circuits could be useful only if they can be implemented with today and tomorrow technologies [7].
For many years MOSFET has been used as a basic element of circuit designing. As the miniaturization of silicon based circuits reaches its physical limitations, molecular devices are becoming hopeful alternatives to the existing silicon technology DOI: 10.3786/nml.v2i4.p227-234 http://www.nmletters.org [8,9]. Especially, unique characteristics of CNT such as high mobility of electrons, high I ON /I OFF ratio and their unique one dimensional band structure that suppresses back scattering and near ballistic or ballistic operation has made it as a potential successor to silicon technology [10,11]. MOSFETs, it has also some drawbacks, such as the problems in the process of fabricating the CNFETs on currently available CMOS platform. For instance, in the integration process, local-gate CNFET is essential. However, most of the local-gate designs use metal as the gate and it is quite hard to combine the metal gate and the grown CNTs for the integration due to the metal melting point limit [12]. In addition, since carbon nanotube network films are composed of both semiconducting and metallic CNTs, CNFETs fabricated based on CNT network films may not turn off completely, which can be troublesome for integrated circuit applications. However, encouraging researches are being performed to solve these physical problems and challenges in the time to come.
Since the I-V characteristics of CNTFETs are qualitatively similar to MOSFET, most of MOS circuits can be translated to a CNTFET based design. As one of the hopeful new devices, CNTFET avoids most of the basic limitations for conventional silicon devices [8,9]. In this paper, we use single-walled carbon nanotube (SWCNT) that can be visualized as a sheet of graphite which is rolled up and joined together along a wrapping vector 2 2 1 1 a n a n h C     , where   2 , 1 a a are lattice unit vectors , and the indices (n 1 , n 2 ) are positive integers that identify the chirality of the tube [13]. Length of C h is thus the circumference of the CNT, which is given by: 22 1 1 1 2 h C a n n n n    (1) Single-walled CNTs are classified into one of the following three groups, depends on their chiral number (n 1 , n 2 ): (1) armchair (n 1 = n 2 ), (2) zigzag (n 1 = 0 or n 2 = 0), and (3) Chiral (all other indices) and here we use CNT with the chiral numbers (17,0) and (19,0) Carbon Nano Tube Field Effect Transistor (CNTFET) The electrons in CNT are confined within the atomic plane of graphene. Due to the quasi-1D structure of CNT, the motion of the electrons in the nanotubes is strictly restricted. Electrons may only move freely along the tube axis direction. As a result, all wide angle scatterings are prohibited, and only forward scattering and backscattering due to electronphonon interactions, are possible for the carriers in nanotubes.
The operation principle of CNTFET is similar to that of conventional silicon devices. This three (or four) terminal device consists of a Semi-conducting Nano-tube, which is acting as conducting channel, and bridging the source and drain contacts.
So, the device can be turned on or off electrostatically through the gate. The quasi-1D device structure provides better gate electrostatic control above the channel region than 3D and 2D device structures. In terms of the device operation mechanism, CNTFET can be categorized as either Schottky Barrier (SB) controlled FET (SB-CNTFET) or MOSFET-like FET [8,9].
The conductivity of SB-CNTFET is controlled by the majority carriers tunneling via the SBs at the end contacts. The on-current and consequent device performance of SB-CNTFET is determined by the contact resistance due to the existence of tunneling barriers at both or one of the source and drain contacts, instead of the channel conductance. SB-CNTFET exhibits ambipolar transport behavior [11]. The work function induced barriers at the end contacts can be made to increase either electron or hole transport. Consequently both the device polarity the conductivity, is modulated by the gate-source bias. Although good DC current can be achieved by SB-CNTFET with the self-aligned structure, its AC performance is going to be poor due to the nearness of the gate electrode to the source/drain metal.
The ambipolar behavior of SB-CNTFET also makes it undesirable for complementary logic design. Taking into account both the fabrication achievability and higher device performance of MOSFET-like CNTFET as compared to SB-CNTFET. The CNTFET that used in HSPICE model is MOSFET-like CNTFET.

CNTFET and Current Mode Logic
In many applications, device speed is the most important requirement, and so conventional voltage mode silicon based devices cannot solve this necessity. Many years ago the current mode logic is proposed as a potential solution for this problem but combining this logic and MOSFET technology reduces the speed advantage pertains to the current mode logic, and furthermore have additional imperfection due to using MOSFET technology. In recent years, this technology has been entered in nano scale region as continues to scale deeper into the nanoscale, device non idealities cause I-V characteristics to be substantially different from well tempered MOSFETs that increase the deficiencies of using silicon based technology.
In the last few years, the research on nanotechnology has been increased particularly on the nanoelectronics. Carbon Nano-tube (CNT) technology is at the front of these technologies due to the unique mechanical and electronic properties [15,16].

Five New MVL Current Mode Differential Absolute Value Circuits Based On Carbon Nano-tube Field Effect Transistors
In the following designs, we used N-type CNTFET current mirrors which act as truncated difference. The main component of all these designs is the truncated difference and its operation is defined as follows: The circuit design of truncated difference is showed in Fig.1.
In some of these designs we used N-type CNTFETs for unidirectional current to the output and P-type CNTFET current mirrors due to inversing the current direction to achieve the appropriate current output direction. These circuits exhibit the arithmetic operation |input1-input2|. Input1 and input2 are the main inputs of our designs. If input1<input2 then the output will be equal to "input2-input1" else we will have "input1-input2" at the output node. The Z1 and Z2 are connected to Z which describes our final output. In our simulation results we apply 10 µA as the highest current level in input1 and we will have 14 µA as the highest current level for the second input (Fig.2). Four CNTFET current mirrors have been used in this design which three of them are N-type and the other one is P-type. By using M7 we will have the copy of drain current of M3. This circuit has two input, and also we used a copy of them in our design. In this design Z1 is connected to the drain node of M6 and Z2 is connected to the source node of M9.
When input1<input2, M1 and M2 will be turned on and base on KCL law the drain current of M3 is equal to zero, hence base on current law the M4 and M7 will be cut off, i.e. their drain current are equal to 0. The drain current of M5 is equal to input1 and the drain current of M6 is equal to input1 (current mirror) and therefore the output Z1 is "input2-input1". When M7 is cut-off then M8 and M9 will be cut-off and we haven't any current in Z2 and finally the output is equal to "input2-input1".
When input2<=input1, M1 and M2 will be turned on and base on KCL law the drain current of M3 is equal to "input1-input2", therefore the drain current of M4 is equal to "input1-input2". Base on KCL law the drain current of M5 is equal to "input2" and the drain current of M6 is the same as previous (equal to "input2") so that Z1 is equal to 0. The drain current of M7 is equal to "input1-input2" and the P-type current mirror will inverse the current direction and the output Z2 and thereby the circuit output will be equal to "input1-input2" (Fig.   3& Fig. 4).

Design 2
In this design we used one P-type CNTFET current mirror for inversing the current direction, and by connecting the gates of M2 and M5, we have two copies of drain current of M1 in drains of M2 and M5 which act as truncated and one N-type CNTFET which its drain and its gate are connected to each other and its duty is unidirectional current from drain node of M5 to the output. This circuit has two inputs that in this design we need a copy of one of them too. In this design the currents of Z1 and Z2 come from the source node of M6 and the drain node of M4.
When input1<input2, M1, M2 and M5 are turn on and base on KCL law and truncated difference the current equal to "input2-input1" comes from M2 and M5 drain nodes and enter to the drain nodes of M3 (upper section) and M6 (lower section) respectively but M3 and therefore M4 are cut-off (P-type current mirror) and hence the upper path is cut-off too and Z2 is equal to 0. In lower path the current equal to "input2-input1" that comes from drain node of M5 can pass through M6, so that Z1 is equal to "input2-input1" and finally the circuit output will be equal to "input2-input1".
When input2  input1, M1, M2 and M5 will be turn on and in this situation M6 is cut-off and the drain current of M6 is equal to 0, therefore the lower pass is cut-off too and we haven't any current in Z1, and base on KCL law and truncated difference the current equal to "input1-input2"enter to the drain node of M2 and the P-type current mirror will inverse the current direction to the output Z2 and thereby the circuit output will be equal to "input1-input2".
In this design the existence of M6 is important, because if we eliminate this transistor and replace it by a wire when input2  input1 the lower path will be open and a current can enter to the drain node of M5, hence the output current will reduce and our circuit will not work properly ( Fig. 5 and Fig. 6).

Design 3
In this design we have two truncated difference circuits and two P-type current. This circuit has two inputs and a copy of them. The currents of Z1 and Z2 exit from the drains of M8 and will enter to the drain node of M6 and the P-type current mirror will inverse the direction of this current to the output Z1 and we will have the current equal to "input2-input1" in the output of our circuit.
When input2  input1, the function in the upper and lower sections of this circuit design will swap and the output of circuit will be equal to "input1-input2" (Fig. 7, Fig. 8).

Design 4
Two N-type CNTFET current mirrors which operate as truncated difference and two N-type CNTFET that in each one their gates and drains are connected to each other and conduct a unidirectional current from drain nodes of M2 and M5 to the output are the components of this circuit design. This circuit has two inputs and a copy of each one and the currents of Z1 and Z2 exit from the sources of M6 and M3 respectively.
When input1<input2, M1, M2, M4 and M5 are turn on and base on KCL law and truncated difference the current equal to "input2-input1" exit from the drain node of M2 and thereby the M3 will be turn on and can conduct this current to the output, therefore the current of Z2 is equal to "input2-input1". And in the lower section of this circuit there is no current in the drain of M6 and thereby in the output Z1. Finally the sum of Z1 and Z2 which is the circuit output is equal to "input2-input1".
When input2<=input1, the operations of upper and lower section of this design will swap, i.e. Z1 and Z2 will be equal to "input1-input2" and "0" respectively and therefore the circuit output will be equal to "input1-input2" (Fig. 9, Fig. 10).

Design 5
One N-type CNTFET truncated difference and one P-type CNTFET current mirror and one N-type CNTFET that its drain and its gate are connected to each other for the unidirectional This circuit has two inputs, and Z1 and Z2 are connected to the source of M3 and to the drain of M5 respectively and their current will be sum at the output node and the result of this sum is the output of the circuit.
When input1<input2, M1 and M2 will be turned on and base on KCL law and truncated difference the current equal to "input2-input1" exit from the drain node of M2 and thereby M4 and M3 will be cut-off and turn on respectively, therefore the M5 which its gate is connected to the gate and drain of M4 will be cut-off too, hence we haven't any current in the output Z2. In this time the current equal to "input2-input1" will pass through M3, therefore output Z1 and thereby the output of our circuit will be equal to "input2-input1".
When input2<=input1, M1 and M2 will be turn on and the current equal to "input1-input2" enter to the drain node of M2, hence we have no current in the drain of M3 and consequently it will be cut-off, therefore output Z1 is equal to "0". In this situation P-type current mirror will inverse the current direction and the current equal to "input1-input2" will be at the output Z2 and thereby at output of our circuit.
In this design the role of M3 is important. If we eliminate this transistor and replace it by a wire when input2<=input1 we will face with some problems: In some amount of inputs either some of drain current of M5 which must enter the output completely maybe enter the M2 drain node and proper output will be reduced and changed, or some of drain current of M4 that must enter to the drain node of M2 completely maybe enter the output and the output will be increase, in these situations we will not have proper output in our circuit output. We reduced the diameter of transistor M3 by changing the chiral number to (n1=9, n2=0) and thereby the threshold voltage of this transistor has been raised, because when the current comes from M4 drain and must enter to the M2 drain completely, some of this current can pass through M3 and enter the output which rise and change the proper output that rising threshold voltage of transistor M3 can solve this problem (Fig. 11, Fig. 12).

Simulation Results
In this paper we have used Carbon-nanotube Field Effect Transistors SPICE Model which is implemented based on "A Circuit-Compatible SPICE model for Enhancement Mode Carbon Nanotube Field Effect Transistors" [8,9,17]. This  For gate length longer than 100 nm, the device is treated as long channel device. The transition from the short channel model (10 nm  Lg  100 nm) to the long channel model (Lg > 100 nm) is continuous and is automatically handled by the model [8,9].
The CNTFET on-current can be approximated as: The parameter n is the number of CNTs per device, V th,CNT is the threshold voltage and is about 0.3V for chirality (19,0) semi-conducting CNT, g CNT is the transconductance per CNT, and L s is the source length (doped CNT region), and ρ s is the source resistance per unit length of doped CNT. CNTFET device delay CV/I can be shown as: The gate to channel capacitance C gc,CNT is the capacitance per unit CNT length [8,9]. We define the pre-factor η CNT as: CNT L ss CNT R   (7) C gtg is the gate parasitic coupling capacitance connected between the gate and the source/drain/ground or the gate of the adjacent devices, according to the device layout. Therefore the CNTFET device intrinsic speed is degraded by both the pre-factor η CNT,C due to the gate parasitic capacitance and the pre-factor η CNT,R due to the extension series resistance.
Due to the transistor sizing and the set chiral numbers for the CNTs, i.e. (17,0) for P-FETs and (19,0) for N-FETs, to make the circuits operate correctly, the N-FETs operate faster than the P-FETs, in the proposed circuits. Therefore, in spite of using 9 transistors in design 1, this design has lower power consumption and delay rather than design3 which has been used 8 transistors.
This is due to the fact that in design3 four P-type transistors are used whereas in design1 two P-type transistors are used. Design4 has lower delay and power consumption compared to design1 because less number of transistors (6 transistors) is used in that design and also the critical path of design1 is longer. Design4 has two copies of each input whereas design2 has two copies of one of the inputs and one copy of the other one. This cause more current flowing in design4, which brings about more power consumption of design4 compared to Design2. Because of using two P-type transistors in design2, this design has more delay than design4. Design5 has the lowest power consumption considering the proposed designs because this design has just 5 transistors and no extra copies of the inputs. However, this design has more delay in comparison with design4 because two P-type transistors have been used in design5.

Conclusion
In this paper we presented five designs of MVL current starch and cellulose derivatives to address these challenges and were shown to have good film forming properties [5].
Acetylated galactoglucomannan (AcGGM) hemicellulose was found to be an excellent candidate for making new renewable barrier materials [6]. The oxygen barrier permeability of the AcGGM films were found to be similar to, or lower than, the values reported on oxygen barrier films made from glucuronoxylan [7] and other polysaccharides, such as starch [8], chitosan [9] and mixtures of various polysaccharides [10].
Hartman reported oxygen permeability of 2.0 cm 3 μm/m 2 dkPa for GGM-sorbitol film [6]. The oxygen barrier properties of films obtained from a mixture of O-acetyl-galactoglucomannan and either alginate or carboxymethylcellulose were also studied.
The reported values of oxygen permeability of GGM/alginate/ DOI:10.3786/nml.v2i4.p235-241 http://www.nmletters.org glycerol blend were 4.6 cm 3 μm/m 2 dkPa [6]. The oxygen permeability of the GGM films was lower than that of glycerol-plasticized amylose and amylopectin films [11], but not as low as that of sorbitol-plasticized aspen glucuronoxylan films [7,12]. The oxygen permeability of oat spelt arabinoxylan films plasticized with 40% sorbitol was 4.7 cm 3 μm/m 2 dkPa, which is slightly lower than that of GGM films [13]. Biobased free-standing films and coatings with low oxygen permeability of 1 cm 3 μm/m 2 dkPa have been also prepared from a wood hydrolysate [14]. Films made from these polysaccharides are brittle and therefore to form cohesive films requires plasticizers such as sorbitol and xylitol. However, even with the plasticizers, the mechanical properties of these films have been considered to less than desirable. Nanocrystalline cellulose has been studied as reinforcements of various synthetic and some natural polymer matrices [15][16][17] to improve the strength properties owing to their high bending strength of 10 GPa, and elastic modulus of 143 GPa [18][19]. Lagaron et al. [20] discussed the role of crystalline structure of polymers and emphasized that high crystallinity improves barrier properties. Nanocrystalline cellulose is greater than 60% crystalline [21][22] and this property together with the resulting rigid hydrogen-bonded network of nanocrystallinecellulose can cause an increase in tortuousity and smaller pore size for nanocomposites which may be utilized to create high barrier materials. In a recent study, spruce galactoglucomannans (GGM) and konjac glucomannan (KGM) were mixed with nanocrystalline cellulose (NCC) to study the mechanical and barrier properties of the films [23,24].
The tensile strength of unplasticized KGM films increased by 30% but the mechanical properties of the plasticized films were not affected with increased in nanocrystalline cellulose. The presence of 5% of nanocrystalline cellulose did not significantly affect the oxygen permeability of the films.
Xylan is one of the most common hemicelluloses, is the most abundant polysaccharide in nature after cellulose, and is an attractive resource for film production [25][26][27]. Prior studies by Saxena et al. [28]  properties with respect to films prepared solely from xylan/sorbitol, and a 362% reduction in water transmission rate with respect to xylan films reinforced with 10% softwood kraft fibers [29]. The objective of the current study is to evaluate the oxygen barrier properties of xylan-nanocrystalline cellulose composite films.

Materials
Oat spelt xylan was obtained from Aldrich and was determined to contain 81.0% xylose, 9.8% arabinose, 7.6% glucose, 1.4% galactose and 0.2% of mannose. A commercial elemental chlorine-free (ECF) bleached softwood (SW) kraft pulp was used as received. Dialysis tubes were purchased from Spectrum Labs. All other reagents and solvents were purchased from Aldrich and used as received.

Preparation of Nanocrystalline Cellulose
Nanocrystalline cellulose was prepared following the procedure outlined by Pu [30].

Characterization
The cross-section and surface morphology of the composite films were analyzed by Hitachi S800, thermally assisted field emission (TFE) scanning electron microscope (SEM) with an accelerating voltage of 12 kV. The samples were sputter-coated with gold prior to examination. Nanocrystalline cellulose and the composite films were analyzed using Dimension 3100 scanning probe microscope and Nanoscope III controller. The images were acquired in tapping mode in air using a 1-10 Ω cm phosphorus (n) doped silicon tip with the cantilever resonance frequency of 150 kHz. Scans were done at 5 microns.

Oxygen permeability Analysis
The oxygen transmission of the films was measured using a Mocon Ox-Tran 2/21 l apparatus (Modern Controls Inc., Minneapolis, USA) with a coulometric sensor in accordance with ASTM method D 3985-95 [32].

Mercury Intrusion Porosimetry Analysis
Micromeritics' AutoPore IV 9500 Series was used to measure the porosity, bulk density, and average pore diameter and tortuosity factor of the control and nanocomposite films.

Results and Discussion
This study examines the oxygen barrier properties of xylan-nanocrystalline cellulose composite films. By AFM analysis, the sulfonated nanocrystalline cellulosic were observed to have rod like structure with an average length of 150-200 nm and a width of less than 20 nm (Fig. 1 [33] and the films made from microfibrillar cellulose [34], see Table 1. Oxygen permeability values were calculated by dividing the oxygen transmission rates by the differential partial pressure of oxygen across the film (1 atm or 101.3 kPa) and multiplying by the film thickness in microns [5]. Table 2 summarized the oxygen permeability of some of the literature work and current work. The oxygen transmission rates as summarized in Table 1 at 25% and 50% dosage of nanocrystalline cellulose decreased drastically with respect to control xylan films and are the two lowest values that we obtained in this study. It will be an interesting subject to explore the porosity, bulk density and tortuosity factor at these two levels and the control xylan films.
As summarized in Table 3, the density and tortuosity factor of the composite film increased while the pore diameter and porosity decreased as the loading of sulfonated nanocrystalline cellulose increased in the xylan-based films.
SEM images of the control xylan film surface showed agglomerated structures on the surface in comparison to a more uniform surface for the nanocrystalline cellulose-xylan films ( Fig. 3 (a) and 3 (b)).
Oxygen transmission rate at 5% and 10% charge of nanocrystalline cellulose doesn't differ much but a significant drop of transmission rate as compared to control. We studied xylan-10% nanocrystalline cellulose film under SEM (Fig. 3) and AFM (Fig. 2b) and found that control xylan film surface in Fig. 3 (a) shows agglomeration in comparison to well dispersed sulfonated nanocrystalline cellulose on xylan surface in Fig. 3 (b). The uneven structure and agglomeration of the xylan can be the cause of higher oxygen transmission rate of control xylan film in comparison to xylan reinforced with 10% sulfonated nanocrystalline cellulose.
SEM cross-section images of freeze fracture of control xylan films showed a rough texture with small cracks in the film as summarized in Fig. 4(a) and 4(b). The same analysis for the xylan film reinforced with nanocrystalline cellulose exhibited smooth fractured surface and less porous structure (see Fig. 4(c) and Fig. 4(d)).  Oat spelt arabinoxylan films plasticized with 40% sorbitol 4.7 [13] Biobased free-standing films and coatings from a wood hydrolysate 1.0 [14] Xylan + 50% sulfonated cellulose whiskers 0.1799 (current study)    [24][25][26][27][28]. The color shift is believed to be originated from the shift of recombination zone with increasing voltage and easier formation of high energy excitons at higher voltage [29].
Recently, highly efficient WOLEDs using phosphorescent materials with incorporated heavy metal complexes have been reported [12,27]

Experimental
The configuration of the devices is ITO/N,N'-bis-   The typical EL spectra of devices A, B and C are presented in Fig. 3      pathologies. In particular, it is one of the naturally-occurring processes in joint or bone surgery, when a prosthesis is cemented into the operation site. Perioperative NSAIDs may then be prescribed to reduce the pain in both the short-and long-term surgical outcomes [2] or even to reduce the risk of postoperative ectopic bone formation [3,4]. Nevertheless, the oral adminis-tration of NSAIDs is correlated with severe adverse gastrointestinal complications and excessive wound bleedings [5,6].

Results and Discussion
Nanotechnology may confer capability for prolonged and effective delivery of drug as a part of prosthesis surface functionalization.
Such nanoobjects, facing a complex and sensitive biological system as the human body, should meet manifold and extremely challenging requirements, such as biocompatibility, biodegradability, and atoxicity [7]. Furthermore, the production process should be simple, near-net-shape, sterile and easily scalable for cost-effective industrial production.
Following these aforementioned requirements, we aimed at designing NSAIDs-loaded biodegradable nanoparticles to be further coated onto prosthesis surface, in order to allow the local and controlled release of the selected NSAIDs. Poly(lactitde-co-DOI:10.3786/nml.v2i4.p247-255 http://www.nmletters.org glycolide) (PLGA) has been extensively studied for drug delivery applications as nanoparticle matrix material because of its recognized biocompatibility and biodegradability [1]. Various methods have been designed to prepare PLGA nanospheres [1,7]. Among them, the Spontaneous Emulsification-Solvent Diffusion (SESD) method is a choice methodology since it is simple, low-energetic and reproducible [8]. Nevertheless, it generally implicates at the best class-3 residual solvents (such as acetone), which involves an additional purification and quantification step. In this preliminary formulation study, we aimed at optimizing this single-step, ready-to-use methodology with the restrained use of completely pharmaceutically-accepted components. A bottom-up, step-by-step strategy was applied to produce NSAIDs-loaded poly-(lactide-co-glycolide) (PLGA) nano-particles, with desirable NSAIDs payloads and release profile. In this respect, the process feasibility and pitfalls were explored through the systematic assessment of formulation parameters and physicochemical characterization.

Morphological studies
The shape and surface morphology of the PLGA nano-

NSAIDs quantification
For drug loading measurement, NSAIDs-loaded nanoparticle suspensions were centrifuged at 23,000 rpm and the Values were reported as the mean ± sd of four replicates.

Results and discussion
Prior examining and discussing the outcomes of various factors on the nanoparticle formation, it is important to state that spherical, individualized nanoparticles were obtained in a wide range of process conditions with fabrication yields over 90% ( Fig. 1). TEM photographs showed a well-defined spherical particle shape, without noticeable aggregation ( Fig. 1(a)). AFM images showed smooth nanoparticle surface ( Fig. 1(b)). AFM also enabled us to precise the core-shell structure of the nanoparticles, as demonstrated by the possibility for the AFM tip to depress them upon contact ( Fig. 1(c)). Nevertheless, it was not possible, with the use of present equipment, to quantify these phenomena. desirable for the considered therapeutic application, which can be reached through monodisperse size populations [12].

Influence of process parameters on the nanoparticle characteristics
Preliminary studies on nanoparticle formation revealed that, to reach this goal, the critical factors during processing were lactide-to-glycolide ratio and polymer concentration. Other factors with great impacts on the final results were also examined, such as solvent/non-solvent volume ratio and tensioactive co-precipitation. Herein, solvent and non solvent refer to the ability to solubilize the polymer, solvent being glycofurol and non solvent being water, more or less enriched with tensioactive molecules.

L/G ratio
The influence of the lactide-to-glycolide (L/G) ratio on particle size is summarized in Table 1, for similar molecular weights and a fixed polymer concentration. A clear trend of increasing particle sizes (as well as polydispersity indexes, PdIs) with increasing the L/G ratio was observed. This phenomenon was previously reported with many types of polyester dissolved in a large variety of solvents, in the solvent diffusion process [13,14]. In fact, an increase of the L/G induces an increase of polymer hydrophobicity due to a higher lactide percentage. This would, in turn, result in increased polymer-polymer interactions, and consequently larger particles. Finally, a higher proportion of lactide units leads to a larger relative amount of crystalline micro-domains in its solid state [15]. When the polymer precipitates during desolvation, such lactide domains would present more difficulties to fold and re-arrange in dense spherical features, leading globally to bigger particles. For these reasons, PLGA 50:50 was selected as the most suitable polymer in this study.
In this respect, the polymer concentration was varied in order to alter the inner solvent phase viscosity and, consequently the solvent diffusion rate into the non-solvent phase [17]. Contrary to what was generally observed [17][18][19][20][21], a linear response between polymer concentration and hydrodynamic diameters was not observed in this study ( Fig. 2(a)). On the opposite, there seemed to be a critical PLGA concentration (with our protocol 2 % w/v) above which the hydrodynamic diameters and PdIs were characterized by erratic values. This phenomenon was already observed in the case of nanoparticles produced by spraying PLGA-glycofurol solution into water [22]. It was as if the solvent molecules were being able to diffuse normally into the non-solvent phase until a critical polymer concentration was reached, which blocked the small solvent molecules into the folded polymer chains. This could demonstrate that the diffusion process is hampered by the affinity between solvent molecules and polymer chains, i.e. the balance between forces involved into polymer solvation and the ones involved into solvent diffusion, as stated by Choi et al. [23]. Further investigations were therefore conducted with a 1.5% PLGA concentration.  Results are given as means ± sd, n = 3 to 9.
Overall, for a fixed 1.5% PLGA concentration, sizes decreased with decreasing the S/NS ratio, until a minimum was reached around 7%. In our system, phase transfer was not instantaneous since glycofurol was more viscous than water (8-18 vs 1 mPas at 20°C [9]), resulting in a transient solvent concentration gradient into the non-solvent phase. Even if sink conditions were globally assumed, increasing the glycofurol/water ratio led to larger particles. This could be due to a locally solvent-saturated system at the interface, slowing down glycofurol diffusion [23] and therefore tending to favour nanodroplet collapses. This was partially visible through the evolution of zeta-potentials ( Fig.   2(b)), which were far more negative for lower ratios than higher ones. This testifies for the presence of glycofurol molecules contributing to the double solvation layer when desolvation is not complete. Nevertheless, for a large scale of volume ratios, particles remained in the range of 200 nm or less. The presence of a plateau in the size evolution (for glycofurol/water ratio smaller than 7% v/v) reveals the existence of a maximal surface curvature, which could not be increased whatever the ratio.

Influence of tensioactive-polymer co-precipitation
The development of stealth nanoparticles as drug carriers, which could avoid or at least reduce the uptake by phagocytes and therefore an immunogenic response, has been thoroughly examined in the last decade [24,25]. It is now well established that the adsorption of blood proteins (leading to surface opsonisation) on hydrophilic surfaces is greatly delayed compared to hydrophobic ones [25]. Surface adsorption or polymer grafting are general methods of choice to turn an hydrophobic surface (such as PLGA) into a more hydrophilic one, using either long hydrophilic polymer chains (like polysaccharides or PEG) or non-ionic surfactants (for example PVAL, poloxamers and poloxamines). In this prospect, the co-precipitation approach developed by Alonso and co-workers is particularly interesting. They initiated a technique in which either poloxamines (Tetronic® 904 and 908) or poloxamers (Pluronic® F68 and L121) were co-dissolved in the solvent phase and nanoprecipitated into an aqueous phase [26]. During precipitation, the tensioactive molecules placed at the solventnon solvent interface were trapped by physical entanglements with polymer chains. In this study, we applied this approach to DOI:10.3786/nml.v2i4.p247-255 http://www.nmletters.org Table 2 Characterization of NSAIDs encapsulation with the optimized formulation (means of n=3, standard deviations between brackets) Drug quantity Size nm (± sd) PdI  zeta-potentials mV  This can happen until the limit is reached (Fig. 2(c)), limit which is controlled by: 1-the presence of polymer chains inside the nanodroplets; 2-the maximal surface curvature observed for this system.

NSAIDs encapsulation
NSAIDs-loaded nanoparticles were prepared from the optimized formulation, with a PLGA 50:50 :P188 1:1 ratio and a S/NS volume ratio of 6.6%. In the absence of P188 in the S (glycofurol) phase, total nanoparticle flocculation occurred between 0 and 24 h post-synthesis. In the presence of P188, the nanoparticle recovery yields varied with the drug concentration in the S phase as well as the observed sizes, while zeta-potentials remained globally unchanged (  Several factors affect the shape of the release pattern [31,32]. The drug release from PLGA particles may depend on three primary mechanisms, i.e. polymer swelling, drug diffusion through polymer network, and polymer degradation via hydrolysis [32]. For high molecular weight PLA and PLGA systems, the diffusion process is dominant and principally drives the initial burst release mechanisms [33]. The second phase is more generally attributed to uniform degradation and erosion of the particle wall, modulated through the solvent diffusion and subsequent enrichment of the external medium [34]. Surprisingly, the role of the nature and diffusion kinetics of the remaining solvent molecules inside the nanoparticles is scarcely discussed.
In the case of nanocapsules, this role cannot be neglected since it constitutes a major component of

Conclusion
The aim of the study was to design stealth NSAID-loaded polymeric nanoparticles according to a one-step nanoprecipitation process to be further coated onto prosthesis surface for drug controlled release. To our knowledge, the use of parenteral solvent glycofurol to produce PLGA-based drug delivery systems is scarce and mainly concerns with macro-or microscopic systems [38][39][40][41]. Glycofurol-based nanoparticles have only been reported once before this work, by spraying PLGA solution into water, with a lesser success in terms of particle production, size and drug loading efficiency [22].
In this work, the influence of various processing variables

Method of Solution
Spatiotemporal distribution of dopant concentration in the considered SH (see Fig. 1) has been described by the second Here V(x,t) and V * are spatiotemporal and equilibrium distributions of concentrations of vacancies. P(x,T) is the limit of solubility of dopant in SH. The fitting parameters ,  and  depend on properties of layers of SH. Parameter  characterizes degree of radiation damage of SH. Parameter  characterizes doping degree of SH. Parameter  usually is equal to an integer value in the interval   [1,3] (see [2]). In the following let us consider the limiting case, when the number of different complexes (for example, complexes of defects) is negligible in comparison with the number of point defects. Spatiotemporal distribution of vacancies concentration is described by the following system of equation [3]  where I(x,t) and I * are the spatiotemporal and the equilibrium distributions of interstitials, respectively.   [12]), T d is Debye temperature [12],  and  are fitting parameters.
is the bulk density of heat power, which is allocated in MS. The power could be approximated by the function: of the laser pulse, S is the lateral area of SH, and P 0 is the power of the laser pulse. J T (x,t) is spatiotemporal distribution of heat flow. The similar time dependence of power has been considered in [13]. However, the approximation considered in our work leads to simplification of analysis of mass and heat transport.
The Eqs. (1), (3) and (4) are complemented by the following boundary and initial conditions in the form where T r is the equilibrium distribution of temperature, which coincides with room temperature.
First of all let us estimate spatiotemporal distribution of temperature. The parabolic equation has been transformed as x v r L d ass x v L d ass ass Let us determine the solution of the system Eqs. (6) by averaging functional corrections (see, for example, [14].
Substitution of the average value of the functions  (x,t) ( = ,T;  =I,V,L) and their partial derivatives in the right side of the Eqs.
(6) instead of the considered functions gives us possibility to obtained the first-order approximations  1 (x,t) of the functions  (x,t). To decrease steps of the iterative process, let us consider more accurate initial-order approximation (see, for example, [8]).
As such approximation we consider the solutions of the equations of the system (6), which correspond to average values of diffusion coefficients D 0L , D 0I and D 0V , thermal diffusivity  0ass and zero parameter of recombination. The solutions can be written in the form Substitution of the Eqs. (7) into the right side of the equations of the system (6) instead of the functions  (x,t) gives us possibility to obtain the first-order approximations (in the modified method of averaging of function corrections) of the appropriate functions. The algorithm is presented in details in [8] and will not be considered in this paper. The second-order approximations of the functions  (x,t), by using the method of averaging of function corrections can be determined by using the standard procedure (see, for example, [8]), i.e. one shall substitute the sums  2 + 1 (x,t) instead of the functions  (x,t) in the right side of the equations of the system (6). The substitution gives us possibility to obtained the second-order approximation of the functions  2 (x,t). The algorithm is presented in details in [8,14] and will not be considered in this paper.
The parameter  2 is determined by the following relation [8,14],

Discussion
Let us analyze the dynamics of redistribution of dopant in the SH (Fig. 1) for step-wise approximations of spatial distribution of diffusion coefficients of radiations defects and dopant and thermal diffusivity. In the case the approximations can be written as   should be noted, that annealing by laser pulse with optimal continuance could be substituted by some laser pulses with smaller continuance, but with high frequency. It should be noted, that optimal annealing time for the laser annealing case is smaller than optimal annealing time for the volumetric annealing case (see Fig. 5). It has been obtained that annealing times for Fig. 2 almost equal to optimal values of annealing times in Fig. 5. The difference could be explained by two reasons. The first of them is insufficient continuance of annealing in Fig. 2. The second one is finite exactness of mathematical approach.

Conclusion
In this paper we consider pulse laser annealing of radiation x L x n r n nT nT n n LL ass ass ass d ass         Recently, a lot of progress has been made in the field of binding different insulating materials with CNTs e.g. for manufacturing field effect transistors, gas sensors, molecular circuits, switches, etc. [1]. Silica is an insulator and when CNTs is being coated with it, toughness [2], thermal conductivity [3], and nonlinear optical properties can be modified and enhanced [4]. One of the main applications of CNTs is to use them as templates to synthesize other nano-structures such as nanotubes, nanowires and nanorods. In the present paper, we have mainly concentrated to report the fabrication and characterization procedures to synthesize silica-NTs.
The prepared silica-NTs are hydrophilic, biocompatible and photoluminescent. This nanostructure has many applications in bioseparation, biocatalysis, biosensors, drug/gene delivery carriers and optoelectronic nanodevices [16].
In this paper, we report the synthesis procedure of silica@MWCNTs and silica-NTs, and the structure, morphology and size determinations of the produced nanostructures using

Conclusions
The process of silica uniformly coated MWCNTs has been reported. In order to coat MWCNTs uniformly with silica we have used CTAB, as surfactant, and APTES, as coupling agent.
In the following experimental procedure and by using the CNTs Nanobelts of different components with various morphologies have been synthesized, including elements [1,2], oxides [3,4], nitrides [5], sulfides [6][7][8][9][10][11] even ternary compounds [12,13] since Pan et al. first reported the formation of nanobelts of semiconductor oxides in 2001 [14]. With the special geometry shapes and microstructure, the beltlike nanostructures have been the research focus due to their unique physical and chemical properties, such as optical [15,16], electrical [17] and sensor [18,19], field emission [20,21], optoelectronic properties [22][23][24], and so on. Therefore, it is important to obtain the desiring nanobelts with uniform dimensions and sizes and controllable structures for the integration of nanodevices based nanobelt building blocks.  Fig. 1(a) indicates the nanobelts are tens of micrometers in length. has a high purity. The inset in Fig. 2(a) is an EDS spectrum, which is consistent with the XRD pattern result. Raman spectrum from the as-grown nanobelts is shown in Fig. 2(b) the much weaker peak at 521 cm -1 is from Si substrate. The dominate spectrum is 350 cm -1 , which is designated as longitudinal optical (LO) phonon mode. The weaker peak at 271 cm -1 is associated with transverse optical (TO) phonon mode.
Some phonon peaks by these election rules will become stronger in a particular scattering geometry due to all of nanobelts grown along the same direction, the same as that of the wires reported by Lin et al [29].   Fig. 4(a). When tungsten wafer substitutes for tungsten thread as the substrate (see Figure 4(b)), the thickness of ZnS nanobelts are larger and their length became shorter. The inset in Fig. 4   There are many reports about photoluminescence and cathodoluminescence of semiconductor nanostructures [37][38][39][40].
Cathodoluminescence measurement of ZnS nanobelts with large aspect ratio was conducted at room temperature at 5 kV and 70 pA. CL spectrum of the as-synthesized ultrathin ZnS nanobelts is showed in Figure 5,

This emission could be strengthened by adjusting the Mn and
Cd content in ZnS [44]. In our work, no Cd or Mn doping, therefore it is no the case for the reported ZnS nanobelts here.
We propose the emission perhaps happen during electron transit from oxygen vacancy to valence band due to a trace of the addition of Sn element. More systematic studies shall be conducted to full understand the origin of this emission band and shall be reported otherwhere.
In summary, ZnS nanobelts with large aspect ratio have been synthesized by using gold coated Si wafer as the substrate.
The as-grown ZnS nanobelts with high width-thickness ratio are about 10 nm in thickness and tens of micrometers in length.  [10]. It has been reported that the stability of Cu 2 O were greatly altered by the material it was coupled with.
Therefore, the applications of the visible-light-responsive Cu 2 O/TiO 2 composite electrode into photoelectron-chemical fields have become a hot subject [10,14]. Since the conduction band of Cu 2 O is ca. ~1.0 eV more negative than that of TiO 2 , the coupling of the semiconductors should have a beneficial role in improving charge separation and transfer, as given in Fig. 1.
Excited electrons from Cu 2 O can be quickly transported to TiO 2 , arriving at the electron collectors from external circuit [14].  [18,19] have also demonstrated that the increase in length of nanotubes may not contribute positively to the photoelectrochemical performance of electrode materials. Recently, a short TNA (referred as STNA) film electrode prepared via sonoelectrochemical anodization route (anodization under irradiation of ultrasonic wave) was reported by our group [20].
Compared with the long nanotubes synthesized by conventional magnetic agitation technique [15,21], the STNA electrode shows excellent charge separation and transfer properties and desirable mechanical stability.

Preparation of STNA
The detailed methodology of the preparation of short, robust and highly-ordered titania nanotube array have been published in our previous work (see Fig. S1 in Supplementary   Information) [20]. The anodized samples were then rinsed with DI water and dried in air. Subsequently, the as-prepared STNA samples were crystallized by annealing in air atmosphere for 3 h at 450℃ with heating and cooling rate of 1℃/min.

Cu 2 O sonoelectrochemical deposition
The

Apparatus and methods
The photoelectrochemical experiments were performed in a rectangular shaped quartz reactor (20×40×50 mm) using a threeelectrode system with a platinum foil counter electrode, a saturated Ag/AgCl reference electrode and a TiO 2 work electrode.
The supply bias and work current were controlled using a CHI electrochemical analyzer (CHI 660C, CH Instruments, Inc., USA). The photocurrent was measured at a scan rate of 20      ZnO nanowires are one of the most promising materials for optoelectronic applications due to their wide band gap of 3.37 eV and large exciton binding energy of 60 meV [1]. It has been recognized as one of the promising nanomaterials in a broad range of high-technology applications, such as photodetector [2], light-emitting diode [3], gas sensor [4], solar cell [5], and optical modulator waveguide [6], etc. Work in this area has focused on the synthesis and material properties of ZnO nanostuctures, and thus, a wide array of materials are available [7,8]. The properties of these nanostructures, and our ability to assemble them, depend largely on the surface functionalization of such structures.

Results and discussion
Surface-initiated polymerization, generally called ""grafting from"", is an important tool to further develop their chemical and physical properties by covalently graft a wide range of polymer chains onto curved or flat surfaces [9][10][11][12]. In comparison with traditional processes used to prepare polymer coatings, surface-initiated polymerization methods provide numerous advantages, including chemical attachment of the polymer to the surface, [13] preparation of conformal coatings on objects of various shapes [14], and good control over film thickness and composition [15].
One of the most successful processes is ATRP [16][17][18], which offers efficient, well-controlled grafting and narrow molecular weight distributions of the polymers grown from the surfaces. The radical reactions involved in the ATRP process enable a wide range of monomers to be used, leading to polymer-modified surfaces with new functionality [16]. This, together with the halogen end-groups, can significantly enhance the physicochemical compatibility of the resulting composites, making the design and preparation of novel materials with DOI:10.3786/nml.v2i4.p285-289 http://www.nmletters.org tailorable structures and properties accessible. ATRP reactions have already been used effectively to modify the surfaces of many nanostructured, such as silica surfaces [19], the surfaces of gold [20], magnetic nanoparticles [21], and carbon nanotubes [22], in each case, providing stability and/or other desirable surface properties. In contrast to the large body of work detailing the modification of silica surfaces, we are aware of only a few reports of related chemistry with ZnO in which a silane was used to modify the surface [23,24].
In this work, the PGMA was grafted from the initiating was refluxed for 12 h in the presence of CaH 2 and distilled. All the reagents used in this study were of analytic grade.

Synthesis of ZnO nanowires
The synthesis of ZnO nanowires were performed according to the report described previously [25]. 0.3 g ZnCl 2 and 30 g Na 2 CO 3 were successively added into a 100 mL Telfon-lined stainless steel autoclave, which was then filled with distilled water up to 90% of the total volume. The obtained reaction mixture was stirred for an additional 30 min. The autoclave was sealed and maintained at 140C for 12 h. After the reaction was completed, the resulting white products were filtered off, washed with ethanol and hot distilled water for several times, and then dried in a vacuum at 60C for 4 h.

Techniques and measurement
The morphology and structure of the samples were

Synthesis of ZnO nanowires
The synthesis route of the ZnO nanowires was shown in scheme 1. Figure 1

Immobilization of the initiator on ZnO surface
To prepare the polymer brush on the ZnO surface, a uniform and dense layer of initiators immobilized on the ZnO surface is indispensable. Scheme 1 outlines the route to generate the ATRP initiator on the ZnO surface. The α-bromoester initiator on the ZnO substrate was prepared by the self-assembly of 3-aminopropyl triethoxysilane, followed by amidization with 2-BPB. FTIR (Fig. 3 A)  To investigate the content of the polymer on the ZnO nanowires, we carried out the TGA characterization. In the TGA curve of the PGMA-ZnO nanowires (Fig. 4), the weight loss at near 100C is assigned to the release of moister adsorbed.
And the weight loss at the temperature range of 250-550C is assigned to the thermal degradation of the grafted PGMA. As far as the ZnO nanowires (Fig. 4A) is concerned, the weight was nearly not changed. As for the PGMA-ZnO nanowires (after the reaction was going on 12 h) (Fig. 4B), the weight decreased to 32%, which means that the content of the polymer in PGMA-ZnO nanowires was 68%. The kinetics of SI-ATRP Attempts were made to prepare polymer nanotube by removing the ZnO nanowires in hydrochloride acid ， but polymers failed to make well-formed tubes (Fig. 1C), instead forming disordered polymer thin films. We studied ZnO nanowires with different thickness of polymer, but they are never sufficient to give normal polymer nanotubes. We deduced that the soft polymer will be collapsed and adhered together after the template ZnO was removed. The FTIR spectrum of the products (Fig. 3C) is similar to PGMA-ZnO nanowires (Fig. 3B), which indicated that the polymer component was not changed. To prove the ZnO nanowires were removed completely, the product was investigated by TGA. The result (Fig. 4C) shows that the interests in recent years [1][2][3][4][5][6][7][8][9][10][11]. Among the numerous synthesis methods studied so far, fabrication inside rationally designed anodic aluminum oxide (AAO) templates has been proved to be an economic and versatile method to produce nanostructures with great efficiency and precision [2][3][4].  A schematic of the synthesis steps is shown in Fig. 1. The AAO templates were obtained by a well-established two-step anodization process [21][22][23]. The synthesis of copper nanowires was adopted from G. A.
The XRD pattern for the Y-junction Cu NWs (Fig. 5(a)) shows that the Cu NWs have a FCC structure (PDF card number: 04-0836) exhibiting a <110> texture, which is interesting because for bulk FCC structures the most energetically favorable texture is <111>. One of the possible reason is that the adsorption of hydrogen may result in the stabilization of the (110) face during the electrodeposition of NWs in acidic solutions [33].
Moreover, at high overpotential the electrodeposited Cu NWs may undergo a thermodynamic to kinetic transition, producing [110] orientation [34].  TEM sample preparation process [37]. The spotty diffraction rings in Fig. 5  Hydrazine is a highly reactive molecule that can be used in agriculture as pesticides, blowing agents, pharmaceutical intermediates, photographic chemical, water treatment for corrosion protection and textile dyes [1]. Hydrazine is also an ideal fuel for a direct fuel cell system because its fuel electrooxidation process does not bring about any poisoning effects [1,2]. There are several reported techniques for the determination of hydrazine, such as titrimetry [3], potentiometry [4], fluorimetry [1], spectrophotometry [5] and chemiluminescence [6]. Voltammetric method possesses many advantages such as high sensitivity, good selectivity, rapid response and simple operating procedure. Because of the large overpotential of hydrazine oxidation at conventional electrodes, various inorganic and organic materials have been modified on the electrode surface to enhance the electron transfer rate and to reduce the overpotential for the oxidation of hydrazine [7][8][9] groups, such as methanol, carbohydrates and amino acids [10,11].
Over the past decade, one-dimensional (1D) inorganicorganic hybrid nanomaterials have received much interest because of their intriguing properties and potential applications in chemical or biochemical sensors, catalysis and nanodevices [12][13][14][15][16][17][18][19]. These hybrid materials based on the combination of organic and inorganic species exhibit the advantages over organic materials such as light weight, flexibility and good moldability, and inorganic materials such as high strength, heat stability and chemical resistance [20][21][22]. Such features of (1D) organic-inorganic hybrid nanomaterials make them ideal building blocks for a new generation of electrochemical sensors.
Recently, Gong, and his co-workers developed a hybrid of bimetallic-inorganic-organic nanofibers (NFs) for the stripping assay of Hg (II) [23]. Decoration of organic nanowires with metal NPs could be an attractive route to fabricate inorganicorganic hybrid nanomaterials without compromising the functions of the nanowires or nanoparticles [14]. Nanoparticles frequently display unusual physical and chemical properties depending upon their size, shape and stabilizing agents. sensing [24,25]. A 3,3,5,5-Tetramethylbenzidine (TMB), much less hazardous than benzidine and more sensitive as a chromogenic reagent, has been investigated for many years [26].
Doping of TMB-based organic nanofibers (NFs) with incorporating of metals ions is of particular interest. In this paper, we report the electrodeposition of Nickel-2, 6-Diaminopyridine

Chemicals and reagents
TMB and H 2 PtCl 6 were purchased from Merck. HAuCl 4 was obtained from Aldrich. Hydrazine was obtained from Sigma.
KOH, NaOH, KCl and other reagents were analytical grade from Merck. All other chemicals were of analytical-reagent grade and used without further purification.

Instrumentation
Electrochemical experiments were performed via using an

Characterization of the modified electrode by SEM
To investigate the surface structure and the morphology of the modified electrode, we performed SEM. Figure 1 shows the SEM images of as-prepared NFs (A), Au-PtNP/NF/GCE (B) and Ni-DAP/Au-PtNPs/NFs/GC electrode (C). It can be seen that the as-prepared NFs have diameters of ~150 nm and lengths up to several micrometers. Results show that these nanofibers interlaced together. After the subsequent deposition process, one can see that uniform Au-PtNPs aligned along the surface of those NFs. The generated NPs were homogenously distributed in the matrix of interlaced NFs, constructing a 3D interlaced network (Fig.1B). Figure 1C shows the SEM image of Ni-DAP/Au-PtNPs/NFs/GC electrode. As can be seen, the film has a globular structure with relatively homogeneous distribution. The presence of small nanoparticles leads to an increase in the surface coverage for more adsorption of hydrazine and OH ads . This  indicating that Ni(III) is consumed during a chemical step [33].
Moreover, the oxidation peak current of hydrazine at Ni-DAP/Au-PtNPs/NFs/GC electrode was (Fig. 3B), 282 μA, which is 2.2 times larger than that at Ni-DAP/AuNP/NF/GC electrode (Fig. 3C) of 125 μA. As it is seen from Fig. 3, the similar behavior with low sensitivity was observed when hydrazine was oxidized at the surface of Ni-DAP/AuNP-GC electrode (Fig. 3D). The result indicates that the presence of bimetallic Au-Pt inorganic-organic hybrid nanocomposite in the modified electrode supplied a larger surface area to allow more deposition of Ni-DAP complex to oxidizing hydrazine.
In order to optimize the electrocatalytic response of the modified electrode toward the electrocatalytic oxidation of hydrazine, the effect of pH on the peak current and peak potential was investigated. The cyclic voltammograms of the Ni-DAP/ Au-PtNPs/NFs/GC in 7 mM hydrazine at different pH values (8)(9)(10)(11)(12)(13) were recorded. As can be seen from Fig. 4, the peak current gradually increased with the increase of pH and reached a wide maximum at pH 13.
The peak potential shifted to the less positive value with the increase of pH. Since more reproducible results and high catalytic activity of the modified electrode was observed at pH 13, this pH value was chosen as optimum pH for hydrazine determination. The same results have been reported for hydrazine electrooxidation processes [34,35].   Figure 5A illustrates cyclic voltammograms of 6.7 mM hydrazine using modified electrode recorded at potential sweep rates ranging from 5 to 200 mVs -1 . The oxidation current of hydrazine on the modified surface increases linearly with the square root of the potential sweep rate (Fig. 5B), which indicates the mass transfer controlled process. Also, it can be seen that, with the increasing scan rate, the anodic peak potential tend toward positive potentials, suggesting a kinetic limitation in the reaction between the redox sites of the Ni-DAP/Au-PtNPs/NFs/GC electrode and hydrazine. The α value of the electrodic reaction can be evaluated from the following equation [36], where b indicates the tafel slope. Using the dependency of anodic peak potential on the natural logarithm of the potential sweep rate (Fig. 5C), the value of electron transfer coefficient (α) is estimated as 0.47. Also, the obtained value of transfer coefficient from the recorded I-E curve of electrocatalytic oxidation of hydrazine (slope of log I vs. E plot) confirms the above reported value (0.508).

Rotating disk electrode (RDE) voltammetry
The indicates that the limiting current is mass-transport controlled (Fig. 6B). The Levich plots deviated from linearity at high rotation rates, suggesting a kinetic limitation. Under these conditions the Koutecky-Levich equation [37] can be used to determine the rate constant. The limiting current is given by Eq.
(5), l /I lim = 1 /I Lev + 1 /I K (5) where I Lev is the Levich current and I K is the kinetic current. I Lev and I K are defined by Eqs. (6) and (7),

Amperometric detection of hydrazine at modified electrode
Since amperometry under stirred conditions has a higher current sensitivity than cyclic voltammetry, it was used to estimate the low limit of detection. Figure 7A Table 1. As seen, the analytical parameters are comparable or better than results reported for hydrazine determination at the surface recently fabricated modified electrodes [38][39][40][41][42][43][44][45][46].

Interference effect for hydrazine determination
To apply this modified electrode to determine hydrazine in environmental water samples, the influence of common ions for the determination of 7 × 10 -6 M hydrazine was investigated. If these interfering ions cause a relative error of less than 5% for the determination of 7 × 10 -6 M of hydrazine, the interference of these species are negligible. The results are summarized in Table 2. It is shown that most of the investigated ions did not interfere for determination of hydrazine.

Analytical applications
Since the present amperometric method is very sensitive and a small volume of the sample is adequate for the hydrazine determination, the standard addition method is suitable for simple and rapid evaluation of hydrazine. The reliability of the amperometric determination of hydrazine in photographic developer was verified using an iodimetric procedure described in the literature [47]. For this purpose, a 0.05 M iodine solution which was standardized in the usual way with a primary standard of As 2 O 3 or titrisol thiosulfate solution was used. The result of statistical calculation shown in Table 3 indicates good precision and good agreement between the repeatability of the proposed and official methods.

Introduction
A huge amount of researches and development activities have been devoted to nano scale related technologies in recent years.
The NSF (Nano Science and Foundation) predicts the market for nanotech products and services will exceed $1 trillion in the US alone by 2015 [1]. Figure 1 shows shock absorber has increased. This is directly related to the ability to design the compact vehicles with high efficiency.

Review of recent research Nanofluid as coolant
Internal combustion spark and diesel engines are used has observed that the effective static thermal conductivities of Au based nanofluids were independent of part loading [6,7].
Experiments on convection heat transfer of nanofluids were conducted by several research groups [8][9][10][11][12][13]. The experimental results show significant improvements in heat transfer rates of nanofluids. that the heat exchanger efficiency increases with increasing particle concentration because of the higher heat transfer coefficients of nanofluids [35].

Nanofluid as Lubricant
In automobile lubrication applications surface modified nanoparticles dispersed in mineral oils were reported to be effective in reducing wear & enhancing load carrying capacity [18]. They concluded that the nanoparticles could fill rough cracks in a metal wall surface to reduce the coefficient of friction [38].

Nanofluid as fuel additives
The present fuel resources are not going to be around forever with the increase of consumptions, and also the combustion of fossil fuels emits harmful gases like CO, NO x , etc. So most of the scientists and engineers are trying to improve the performance of automobile by using different methods, for example reducing the vehicle weight, improving to improve the fuel economy as well as to reduce the exhaust emissions. The combustion efficiency and the combustion stability will be increased by adding metallic nanoparticles to our commercial fossil fuels. The scientists in nano science and technology council in USA have achieved to increase 1025% combustion efficiency by adding 0.5% of aluminum nanoparticles to a rocket's solid fuel [19]. Also the combustion speed has been increased because of nanoparticle additives. hydrogen. Aluminum nanoparticles serve as a catalyst to decompose the water. They also observed that the fuel consumption will reduce by using aluminum nanofluid and diesel mixture [20]. The experimental investigation was carried out to improve the performance and emission characteristics of C.I engine using cerium oxide nanoparticles with diesel and biodiesel mixture fuel by Arul Mozhi Selven et al. [21]. The cerium oxide acted as an oxygen donating catalyst and provides oxygen for the oxidation of CO or absorbs oxygen for the reduction of NO x . They observed that combustion of the fuel will improve and reduce the exhaust emission by using a cerium oxide nano particle catalyst. The burning characteristics of ethanol droplets containing nano-and micron-sized aluminum particles were investigated by Yanan Gan et al. [39]. In this research aluminum nanoparticles acted as a catalyst. They observed that the fuel burnt completely by suspending the aluminum nanoparticles with the fuel.

Nanofluid in shock absorber
Shock absorbers provided the comfortable ride in vehicles ranging from sports car to pick up trucks. The hydraulic shock absorbers were used in modern automobiles to reduce the space and to improve the performance of shock absorber by absorbing

Conclusion
Nano fluids are important because they can be used in numerous applications involving heat transfer and other applications in automobile. Nano fluids have also been used as smart materials to absorb vibrations in automobiles. The main findings in this paper are summarized as follows.
1. The internal combustion engine performance will improve by 510% by using Nano particle suspended commercial engine coolant.
2. The vehicle life as well as the performance can be increased by enhancing the tribological properties (such as load carrying capacity, wear resistance and friction reduction between the moving components) of nanoparticle suspended lubricants.
3. The combustion of the fuel can improve and reduce the exhaust emission by using a nanoparticle catalyst in commercial fossil fuel.
Further research still has to be on the synthesis and application of nanofluids so that the developing systems will be more efficient, smaller, healthier and environmental friendly.