1 Introduction

In recent times nanoscience and nanotechnology have led to a technological revolution in the world, which is apprehensive with materials with significantly novel and enhanced physical, chemical and biological properties. In this regard, nanoparticles are recognized as antibacterial agents due to their size, structure, and surface properties [1, 2].

Nanomaterials has been widely used in many applications such as transparent conductive films, efficient photocatalysts, varistors, gas sensors, photonics, ceramics, healthcare, cosmetics, food and feed, environmental issue, biomedical application, chemical companies, electronics, drug delivery, energy, optoelectronics, catalysis, single-electron transistors, light emitters, non-linear optical devices and photo-electrochemical applications [3,4,5,6,7,8,9,10,11,12]. It has been shown that the size, morphology, stability and properties (chemical and physical) of these nanoparticles much depend on the preparation technique and conditions they used in the experiment [13,14,15,16,17]. The sol–gel has several advantages such as high purity, ultra- homogeneity, lowering the synthesis temperature and most significantly the possibility of making new compositions [18,19,20,21,22,23,24,25,26,27,28,29] electrical and optical devices [30,31,32,33,34]. Metallic nanoparticles used in pharmaceutical applications such as anti-cancer, anti-parasite, antimicrobial, antiviral activity [35,36,37,38,39]. Multidrug resistant (MDR) bacteria are well-recognized to be one of the most important current public health problems. Some MDR bacteria have become quite prevalent causes of community-acquired infections. The spread of MDR bacteria into the community is a crucial development, and is associated with increased morbidity, mortality, healthcare costs and antibiotic use. Factors associated with community dissemination of MDR bacteria overlap but are distinct from those associated with nosocomial spread [40,41,42]. Recently nanostructured AgNPs have engrossed nice attention owing to their in-depth exploitation in environmental and antibacterial drug activity. The antibacterial agents are used to prevent or kill the growth of bacteria. Ag nanoparticles are good antibacterial drug agents. Chemical constituents present in Garcinia mangostana tannin, a -mangostin, b -mangostin, g -mangostin,somangostin, gartanin, and 8-desoxygartanina a -mangostin, g -mangostin, gartanin, 8-deoxygartanin, 5,9-dihydroxy-2, 2-dimethyl-8-methoxy-7-(3-methylbut-2-enyl)-2 H, 6 H –pyrano [3, 2-b] xanthen-6-one, garcinone E, 2-(g, g -dimethylallyl)-1,7-dihydroxy-3-methoxyxanthone, and epicatechin. Nepheliumlappaceum L. contains fatty acids in seed lipids are arachidic acid, oleic acid, stearic acid, and palmitic acid, protein, fat, and carbohydrates, aminoaid [43, 44]. The excellent antibacterial drug activity of Ag nanoparticles was probed by several researchers [45,46,47,48]. In the modern era, the water is getting depleted by number of pollutants present in the waste effluents from the industries. It is necessary to remove these pollutants from the waste water on the account of their toxicity. The nitro group containing pollutants are of major concern as they are difficult to reduce because of their toxic behavior. But there is a growing demand forfast, effective and improved method for degradation and removal of these hazardous organic dyes.

In recent times, metallic nanoparticles are found to have impressive photocatalytic property for degradation of organic compounds under visible light irradiation [49,50,51,52,53]. Congo red is the sodium salt of benzidinediazo-bis-1-napthyllamine-4-sulfonic acid; It is a diazole dye that is red in alkaline solution and blue in acid solution and used especially as an indicator. Congo red (CR) can also cause allergic dermatitis and skin irritation. Some of them have been reported to be carcinogenic and mutagenic. Karthik et al. describe the photocatalytic properties of SnO2 prepared by green synthesis [54].

Musea ferrea belongs to guttiferae family and is blessed with a variety of medicinal properties and it is a rich source of secondary metabolites. In Asian countries and are traditionally used by the local people for the treatment of various ailments including asthma, cough, dyspepsia, fever, itchiness, nausea and renal diseases. Several pharmacological attributes of Mesua species such as antioxidant, antimicrobial, antiviral, antitumor and immunomodulatory have already been proved (Teh et al. 2012; Asif et al. 2016). The Chemical constituents present in Musea ferrea are α-copaene, germacrene D,ve β-amyrin, mesuanic acid, triterpenoids, resins, tannins, biflavonoids, phenolmesuone.

This paper deals with the synthesis of silver nanoparticles, in the presence of Mesua ferrea seed extract of deploying a biological technique, enabling controlled production of shape-modulated high purity nanoparticles. AgNPs were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV–Vis-NIR spectrophotometry, energy-dispersive X-ray spectroscopy (EDX), DLS and field-emission scanning electron microscopy (FESEM). Both particle types were evaluated for their potential use as a photocatalyst, antibacterial activity.

2 Materials and method

2.1 Materials collected

Silver nitrate (99.9%) was purchased from Sigma-Aldrich. The seeds were collected from the Siddha medicals. Double distilled water was used for preparing aqueous solutions all over the experiments.

2.2 Sample preparation

The seeds were collected from the Siddha medical and washed many times in tap water and dry for 3 days in the sunlight and grind to make a powder. 5 g of powder was taken in a beaker and 100 mL of double distilled water for 20 min at 100 °C. The seed extract was filtered through Whatman filter paper and collected for further process.

2.3 Synthesis of silver nanoparticles

There are various top down and bottom approaches for synthesis of AgNPs. In our present investigation, AgNPs have been synthesized by green synthesized method. Because this method is cost effective, eco-friendly, it required low temperature [57,58,59,60,61,62,63,64].

50 mL of 5 mM silver nitrate (AgNO3) solution was added to 10 mL of seed extract dropwise with constant stirring at 60 °C and colour changes were observed to faint red to brown. This indicates the creation of silver nanoparticles. The extract was then centrifuged at 10,000 rpm for 20 min the pellet was washed two times and calcinated at 200 °C in muffle furnace and the collected powder was then used for characterization and to evaluate antibacterial activity.

2.4 Characterization

The structure of synthesized AgNPs was investigated using the XPERT-PRO X-ray Diffractometer with CuKα1 radiation (1.5406Ǻ). The morphologies were observed by HRTEM (JEOL/JEM 2100F), FESEM (SIGMA HV – Carl Zeiss with Bruker Quantax 200 Z 10 EDS Detector) and equipped with EDS to find the element composition. FT-IR analysis was carried out by JASCO 460 PLUS FT-IR spectrometer in the range of 4000–400 cm−1. Biosynthesized AgNPs were analyzed by using UV–Vis-NIR spectrum (Perkin Elmer Lambda 35). Antibacterial activity of synthesized AgNPs has experimented with Staphylococcus aureus, Bacillus subtilis, and Salmonella typhi, bacterium by agar disc diffusion technique.

The photocatalytic activity of AgNPs was determined by studying the photodegradation of Congo red dye solution under sunlight irradiation. 20 mg of AgNPs was added to 100 mg/L CR aqueous solution and stirred for 30 min and the mixture was kept under for sunlight for 1–3 h the residual CR in the aqueous solution was analyzed by checking the absorbance at 550 nm. The samples were collected at regular intervals (for every 30 min) and the UV–Vis spectrum was recorded. The degradation percentage of the dye in the presence and absence of AgNPs is calculated from the following equation [65].

$$\eta = \frac{{C_{0} - C_{1} }}{{C_{0} }} x100\%$$
(1)

η is the percentage of degradation, Co is the initial concentration of the dye (mg/L) and C1 is the concentration of the dye after irradiation in the selected time interval (mg/L).

3 Results and discussion

3.1 Structural analysis

The synthesized AgNPs were crushed as a fine powder for X-ray diffraction studies. The recorded X-ray diffraction pattern for AgPNs is depicted in Fig. 1. The recorded spectrum of the sample was taken at room temperature in a 2θ range of 0–80° using CuKα1 radiation of wavelength 1.54056 Å. From the diffraction pattern, the d-spacing and hkl values for each diffraction peak in the corresponding spectrum of the sample were identified. Using the face center cubic structure crystallographic equation, the lattice parameter values of AgNPs were calculated and compared with the reported values from JCPDS No. 04–0783. It is confirmed that AgNPs belong to the face center cubic crystal system: the unit cell parameters were found to be a = 4.0715 nm. Some additional peaks were reported the presence of bioorganic matters and the capping for AgNPs for the formation [66].

Fig. 1
figure 1

XRD pattern of AgNPs

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The size of the silver nanoparticles is calculated from the XRD data using Scherrer’s formula:

$${\text{D}} = \frac{{{\text{k}}\lambda }}{{\upbeta \cos \theta }}$$
(2)

The average particle size of the Silver nanoparticles is 15 nm.

Willamson-Hall method is used to find the lattice strain by the modified Scherrer equation

$$\frac{{{\text{dy}}}}{{{\text{dx}}}}\upbeta \cos\uptheta = \left( {{\text{k}}\uplambda /{\text{D}}} \right) + \left( {4\upvarepsilon \, \sin\uptheta } \right)$$
(3)

The W–H plot of βcosθ versus sinθ is shown in Fig. 2. The W–H plot is expected to be a horizontal line parallel to the sinθ axis, whereas in the presence of strain, it has a non-zero slope. The obtained value of microstrain for the silver nanoparticles is 0.00672.

Fig. 2
figure 2

W–H plot of AgNPs

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3.1.1 Dislocation density (δ)

The dislocation density (δ) is calculated using the equation.

$$\delta = \frac{1}{{D^{2} }}$$
(4)

The number of unit cells (n) is estimated from.

$$n = \frac{{D^{3} }}{6V}$$
(5)

where V is the volume of the unit cell

3.1.2 Morphology index

The Morphology Index (MI) is evaluated from FWHM of XRD. MI is obtained using the equation

$${\text{MI}} = {\text{FWHM}}_{{\text{h}}} /{\text{FWHM}}_{{\text{h}}} + {\text{FWHM}}_{{\text{p}}}$$
(6)

where FWHMh is the highest FWHM value obtained from peaks and FWHMp is value of particular peak’s FWHM. The calculated MI values are shown in Table 1.

Table 1 Structural properties of FCC silver nanoparticles
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3.1.3 Relative percentage

The Relative Percentage Error (RPE) is calculated by

$${\text{RPE}} = \frac{{{\text{Z}}_{{\text{H}}} - {\text{Z}}}}{{\text{Z}}} {\text{X}}100$$
(7)

where ZH is the experimental d-values in the XRD pattern and Z is the standard d-values in JCPDS data. The calculated RPE values are presented in Table 1.

3.2 FTIR analysis

The FTIR spectrum was measured with in the 400–4000 cm−1 region using JASCO 460 PLUS FTIR spectrophotometer KBr pellet technique. The FTIR spectrum of AgNPs is shown in Fig. 3. The functional groups are present in the AgNPs and Musea ferrea seed extract contains alkyl, amines alcohols, phenols in the frequency of 500 cm−1–4000 cm−1. The synthesized powder has an intense vibrational stretching 3850 cm−1–3443 cm−1 (–OH) stretching alcohol. The band at 2360 cm−1 identified as C–N stretching (Nitriles), 1633 cm−1 has been observed as N–H bend primary amines. The band at 1384 cm−1 which rose OH bending Phenol, 1068 cm−1 has observed as C–OH stretching alkyl ether 668 cm−1indiates alkynes, primary and secondary amines. This results indicates that carboxyl group, amine and phenols groups are mainly involved in the formation of silver nanoparticles [67]. The comparison of seed extract and AgNPs are shown in Table 2.

Fig. 3
figure 3

FTIR spectrums of AgNPs and Musea ferrea seed extract

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Table 2 Comparison of FTIR bands (AgNPs and seed extract)
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3.3 Morphology studies of agnps

The FESEM image of AgNPs is shown in the Fig. 4a, b and Table 3 shows that the EDX of AgNPs. The peak indicates the Ag of the energy interval of 3 keV. The small quantities of additional elements, including Ca, Na, O, Mg, C and Ag were associated with Mesuea Ferrea seed extract reducing the silver ions. EDX analysis cannot distinguish between elemental Ag and Ag atoms in other compounds. Fig. 4c shows that the HRTEM images of AgNPs which exhibiting spherical this result is corresponding to the result of coffee Arabica seed extract [68]. Most of the diameter of the particles in the range of 18 nm–30 nm for 5 mM sample. SAED patterns show a strong presence of bright spots along with their crystal orientations appearing within the diffraction rings. The bright spot in the SAED pattern for Fig. 6c the crystalline nature and spots in the form of circle designate the polycrystalline nature. SAED that corresponded to the different crystallographic planes of FCC structure of elemental silver are seen in the Fig. 4c. The XRD spectrum of silver nanoparticles (Fig. 1) exhibiting the characteristic peaks of the silver nanoparicles observed at 2θ values 38°, 44o, 64°, 77° corresponding to (111), (200), (220), (311)of silver nanoparticles is also agreed with SAED result.

Fig. 4
figure 4figure 4

a FESEM images of AgNPs, b EDX of AgNPs, c HRTEM and Particle size distribution

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Table 3 EDX analysis of composition from synthesized
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The average number of atoms per nanoparticle by using the formula given below

$$\begin{aligned} {\text{N}} &= \left[ {\Pi {\text{pD}}^{3} )/\left( {6{\text{M}}} \right)} \right]^{*} {\text{N}}_{{\text{A}}} \hfill \\ {\text{N}} &= \left[ {\left( {\Pi \left( {1.05{\text{x}}10^{ - 20} } \right)\left( {11} \right)^{3} } \right)/\left( {6\left( {108} \right)} \right)} \right]^{*} 6.022{\text{x}}10^{23} \hfill \\ &= 4.078 \times 10^{4} {\text{atoms}}/{\text{NP}} \hfill \\ \end{aligned}$$
(8)

3.4 DLS analysis

The DLS pattern of AgNPs is shown in Fig. 5. The particle distribution was carried out using a DLS instrument. The analysis determines average particles size distribution profile of synthesized nanoparticles. In this result AgNPs were polydispersed in nature with the increased diameter of particles in the range of 2.4 nm–100 nm. The larger size particles appeared due the agglomeration AgNPs in the solution.

Fig. 5
figure 5

DLS pattern of synthesized AgNPs using Mesua ferrea seed extract

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3.5 Optical studies of AgNPs

The spectrum was recorded in the wavelength region 190 nm–1100 nm using the Perkin Elmer Lambda 35 spectrophotometer. The recorded optical absorption spectrum of AgNPs is shown in Fig. 6. The absorption spectrum of the silver colloid in the range of 300 nm–900 nm. UV–visible spectrum was absorbed due to the surface plasma resonance; it is due to the formation of silver colloids because AgNPs exhibit an intense absorption peak at 447 nm. As a direct optical band gap is material, the nanoparticles under study as an optical absorption coefficient (α) obeying the following relation for high photon energies hν.

$$\alpha = \frac{{A\sqrt {(h\nu - E_{g} )} }}{h\nu }$$
(9)
Fig. 6
figure 6

Optical absorption Spectrum of AgNPs

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where Eg is optical band gap of the crystal and A is a constant.

The graph between (αhν)2 versus (hν) as shown in Fig. 7. The optical energy band gap (Eg) is estimated as 2.7 eV by extrapolating the linear portion of the graph to meet the energy axis to determine the energy band gap.

Fig. 7
figure 7

Optical bandgap of AgNPs

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3.6 Photo catalytic activity

Figure 9 shows the photodecolourisation of Congo red in the presence and absence of AgNPs photocatalyst under sunlight irradiation. There was no observable colour loss of the dye in the absence of catalyst. Slight decolourisation with the photocatalyst in the absence of light may be due to the adsorption of the dye onto AgNPs Complete decolourisation in the presence of light coupled with photocatalyst clearly indicates that the degradation phenomenon is purely photocatalytic in nature. Molecular formula of Congo red is C32H22N6Na2O6S2 (Fig. 8). The present photocatalytic degradation efficiency is compared with some herbals of AgNPs against Congo red dye (Table 4) and (Fig. 9).

Fig. 8
figure 8

Molecular structure of Congo red

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Table 4 Comparison of photoatalytic activity of AgNPs against congo red
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Fig. 9
figure 9

Presence and absence of catalysts (AgNPs)

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The mechanisms of photocatalytic degradation of Congo red under sunlight as shown in the Fig. 10. Metal nanoparticles support electron transfer from the donor to the acceptor, absorbed photons to excite the valance band electrons to conductions band, due to the reduction of disintegration the dye molecules conduction band electrons and valance band holes ends. On the other hand during the process when the sunlight is absorbed and ROS (O2, OH−, H2O2) radicals are formed and cleaning its surfaces by itself. The photocatalytic activity of AgNPs was determined by deoxidation of CR under the natural energy resources sunlight for 2 h–2.30 h Initially, the degradation in the presence of AgNPs has absorbed visually the intensity of the colour gradually decreased with time increased, colour changes dark orange to light the intensity peak absorbed at 550 nm (Fig. 11). Thus Fig. 10 shows that the effective catalytic degradation of AgNPs in the presence of sunlight is faster.

Fig. 10
figure 10

Schematic diagram of mechanism of photodegradation of Congo red mixed AgNPs

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Fig. 11
figure 11

The Photo catalytic activity of AgNPs

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3.7 Photocatalytic mechanism

The electrons in the conductions band react with the dissolved oxygen to form a superoxide anion radical. At the same time, the holes in the valance band react with the adsorbed water to produced hydroxyl radicals. Finally, the superoxide and hydroxyl radicals interact directly with Congo red dye and degrade it into H2O [71].The photocatalytic mechanisms as follows.

AgNPs (e−CB) + O2 → AgNPs + O2.

H2O → H+  + OH.

O2 + H− → HO2.

Silver nanoparticles (eCB) + HO2 + H + → H2O2.

AgNPs (h+νB) + dye → degradation products.

HO− + H+ → H2O2.

HO2 + e− → HO2−

This result indicates that the silver nanoparticles possess high photo degradation efficiency. The combination of metal nanoparticles generates more active catalytic centres which facilitate the photodegradation performance.

3.8 Antibacterial activity

The antibacterial activity of AgNPs using Mesua ferrea seed extract for different concentrations was carried out by the biological method. The zone of inhibition of bacteria is greater than 26 mm as shown in Table 5. This table shows AgNPs have good antibacterial activity against the tested bacteria. The antibacterial activity depends on the size, specific surface area, morphology, etc., the mechanisms of the antibacterial activity are shown in Fig. 12. The mechanism is quite complex, the generation of ROS formation of free radicals with the bactericidal action of AgNPs by the release of Ag+ ions penetrates negative charge on the cell wall, affect the cell membrane and to disrupt the permeability, damage proteins, and the respiratory of the cell which leads to cell death [72,73,74,75]. The antibacterial activities of FCC shaped silver nanoparticles have good zone inhibition compare with other herbals as shown in Table 6.

Table 5 Antibacterial activity of AgNPs using Mesua ferrea seed extract concentration (10, 20, 30, 40 μg/mL)
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Fig. 12
figure 12

Mechanism of antibacterial activity

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Table 6 Comparison of antibacterial activity for selected human pathogens
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4 Conclusions

The silver nanoparticles were successfully synthesized using the plant extract of Mesua ferrea with high surface area by biological method. XRD results confirmed that the raise in calcinations time resulted in enhance in particle size with a high surface area. The FTIR spectra illustrated the transformation of silver. UV–Vis-NIR absorption spectra revealed that the raise in calcinations time created a blue shift in the spectra, which led to decrease in energy gap with increase in particle size. Based on results, it is concluded that particle size and optical properties are controlled by calcinations time. The morphology and chemical composition were elucidated by FESEM and EDAX. The particle distribution was carried out using DLS studies. In this study, the photocatalytic and antibacterial activity of silver nanoparticles was excellent size 15 nm. It is also concluded that the antimicrobial property of silver nanoparticles increased with increase in surface area to volume ratio due to a decrease in particle size. Hence, smaller sized silver nanoparticles can be used as an antimicrobial agent more effectively. The present study also confirms the antioxidant activity of biosynthesized silver nanoparticles, which can be effectively used as the drug to eradicate free radicals to prevent cellular injury. Due to their high antimicrobial activity, the silver nanoparticles can also be used in the antimicrobial applications. The present study also dealt with the anticancer potential of AgNPs against human lung adenocarcinoma cancer cell line (A549) and normal human epithelial cells (HBL-100), and further study on silver nanoparticles will be carried out for drug delivery, food and pharmaceutical applications.