1 Introduction

To create polymer nanocomposites with diverse characteristics, optimal combinations of nanoparticles and polymer materials are achievable through the unique prospects offered by nanoscience and nanotechnology [1,2,3]. The reinforcement of polymers with fillers of varied sizes is a common practice to mitigate their flaws and enhance their utility [4]. The customization of polymer nanocomposite to exhibit specific properties for distinct applications has garnered significant attention from both academic and industrial experts. The integration of polymer nanoparticles to enhance the mechanical and physical attributes of polymers presents a substantial departure from conventional polymer practices [5,6,7,8,9,10,11]. Furthermore, the appealing physical properties of polymer nanocomposite, including their mechanical robustness, cost-effectiveness, and flexibility, have contributed to their increasing popularity. Diverse types of polymers serve as potential hosts for various types of nanoparticles. The incorporation of nanoparticles into polymer matrices enhances the optical and electrical features of polymer nanoparticles by leveraging the combined properties of organic and inorganic substances. The introduction of nanoparticles into polymers at different concentrations yields nanopolymers with well-dispersed properties. Among the widely utilized polymers, polyvinyl chloride (PVC) stands out [12]. The integration of various nanoparticles into pure PVC enhances its known physical, chemical, and economic properties, such as its electrical properties, ease of preparation, mechanical strength, and excellent insulation, making it more advantageous for a wide array of applications [13,14,15,16,17,18,19]. The enhancement of PVC's physical and mechanical properties has been demonstrated by incorporating graphene oxide and carbon nanoparticles into PVC [20,21,22,23].

Conversely, silver nanoparticles are renowned for their exceptional physical attributes [24] and find increasing application across various domains, including water purification, medical equipment, household sanitization, memory cards, photonics, and thin-film transistor electrodes [25,26,27]. Incorporating silver nanoparticles into PVC polymer films results in polymers endowed with antibacterial properties, offering potential usage as food preservatives [28]. The impact of silica (SiO2) incorporation into PVC polymers has been studied [29]. When incorporating silver nanoparticles (AgNPs) into PVC, the resulting nanocomposites exhibited a change of optical bandgap values compared to pure PVC [30]. By combining polyvinyl alcohol (PVA)/polyacrylamide (PAAm)/polyethylene oxide (PEO) polymer blend with AgNPs, the optical coefficients demonstrated a rise with the augmentation of AgNPs and wavelength, with the exception of the transmittance spectrum and optical energy gap [31]. The combination of PVA, PAM, and polyethylene glycol (PEG) with AgNPs led to significant enhancement in absorbing ultrasonic (U/S) waves. These blend solutions served as an anti-scattering medium instead of traditional sonar and echo gels due to their ease of preparation, affordability, skin-friendly nature, electrical conductivity, and suitability for local production [32]. Blending (PVA-PAAm-PEO) with varying weight percentages of Ag nanoparticles to form nanocomposites resulted in optical properties that were directly proportional to the presence of Ag nanoparticle additives, except for transmittance and energy gap. The optical parameters indicated a clear influence of Ag doping on the film characteristics, leading to enhancements in optical constants [33].

Metal pollutants have been identified as one of the most hazardous environmental contaminants, posing significant threats to both ecosystems and biological systems [34, 35]. They represent a primary cause of water contamination due to their extreme toxicity and non-recyclability [36]. Toxic heavy metal ions (HMIs) like copper, cadmium, mercury, and nickel have direct adverse effects on human health [37,38,39], while their detrimental impact on soil quality ultimately affects both humans and animals [40]. The widespread contamination of water sources by toxic heavy metal ions like cadmium poses a significant threat to human health and the environment. Detecting these toxic ions is crucial and necessitates fast, accurate, and detectable methodologies. Various methods exist for detecting these toxic metal ions which are classified into different categories [36, 41,42,43,44,45,46]. Conventional methods for detecting these pollutants often lack the required sensitivity, selectivity, and real-time monitoring capabilities. Biochemical analyses commonly rely on ultrasonic sensors employing surface plasmon resonance (SPR) technology, offering precise readings characterized by a consistently stable frequency response within a specified range [47, 48]. This study aims to develop a novel polymer nanocomposite based on PVC embedded with silver nanoparticles (PVC@Ag) for highly sensitive and rapid detection of cadmium ions in water samples. It was used to examine the physical properties exhibited by a PVC@Ag nanocomposite containing varying concentrations of Ag nanoparticles. This research aims to elucidate the impact of silver nanoparticles on the physical attributes of PVC polymers. The utilization of PVC matrix enriched with silver nanoparticles is intended for the detection of heavy metal contaminants, specifically targeting cadmium ions. Diverse characterization techniques, including dynamic light scattering (DLS), zeta-potential measurement, assessment of Brunauer–Emmett–Teller (BET) surface area, atomic force microscopy (AFM), alongside scanning and transmission electron microscopes (SEM and TEM), as well as X-ray diffraction (XRD), are employed to evaluate the properties of the nano matrix. The SPR method, particularly efficient in identifying toxic metals like Cd(II) ions, is utilized to assess the efficacy of the PVC nanocomposite. Initial experiments involve subjecting contaminated water samples to SPR analysis using PVC@Ag nanocomposite samples integrated with an Au metallic layer to detect the presence of Cd(II) ions.

2 Materials and Methods

2.1 Materials

Polyvinyl chloride (PVC) was obtained from INEOS Chlorvinyls Ltd. (molecular weight = 48,000 g/mol). Tetrahydrofuran (THF, anhydrous, ≥ 99.9%, inhibitor-free) was purchased from Sigma-Aldrich. Silver nitrate (AgNO3, ≥ 99.0%) and trisodium citrate dihydrate (≥ 99.0%) were acquired from Merck.

2.2 Synthesis of PVC@Ag Nanocomposite

The synthesis of nanocomposite involved integrating hybrid silver nanoparticles into PVC polymer as a recommended procedure. Tri-sodium citrate (TSC) served as both a capping and reducing agent during the co-precipitation process to produce silver nano particles. To initiate the synthesis, AgNO3 solution (0.03 M) was dissolved in 120 mL of deionized water, brought to a boil, and then slowly introduced with TSC while vigorously stirring at 750 rpm, resulting in the mixture turning pale yellow. Following this, the mixture was gradually cooled down to room temperature in a dark environment to prevent light exposure. The PVC@silver nanoparticles were formed by dissolving 5 g of PVC in 100 THF and maintaining stirring at 60 degrees Celsius for a duration of 5 h. Specific quantities of the produced silver nano particles (0.05, 0.1, 0.15, and 0.2 g) were then added to the solution. Subsequently, PVC@Ag nanocomposite samples with varying concentrations (1%, 2%, 3%, and 4%) were cast into glass dishes with a diameter of 10 cm and allowed to dehydrate for a day. The thicknesses of PVC@Ag nanocomposite films were measured by digital micrometer to be 0.9 mm, 1.04 mm, 1.12 mm and 1.28 mm for 1%, 2%, 3% and 4% concentrations, respectively.

2.3 Instrumentation

The Thermo Scientific ARL EQUINOX 1000 X-ray diffraction instrument was employed to determine the phase and composition of the PVC@Ag nanocomposite. The scan rate was adjusted to 0.1°/min, covering a range of 5° to 80° for 2θ angles calibration. Additionally, the NanoSight NS500 instrument from Malvern Panalytical, Malvern, UK, was utilized to assess the surface charge and particle size of the PVC@Ag nanocomposite via zeta potential analysis. Examination of the PVC@Ag nanocomposite morphology was carried out using a JEOL JEM-2100 high-resolution TEM device. Prior to TEM analysis, ultrasonication was performed on the PVC silver nano molecule samples using an UP400S ultrasonic probe device (Hielscher, Oderstraße, Teltow, Germany) for up to 20 min at a frequency of 55 kHz with an amplitude of 55% and for 0.55 cycles. Following ultrasonication, the dispersed mixture was applied onto a carbon-coated copper grid and analyzed via TEM, utilizing droplets measuring five to ten microns. An Agilent Technologies 5600Ls AFM device was employed for AFM examination. Surface area and pore size measurements were conducted using the Quanta chrome NOVA touch 2LX BET Surface Area measurement device. Detailed data regarding chemical structure and physical properties were obtained through Raman spectroscopy (HORIBA LabRAM_HR_Evolution) and UV analysis (Shimadzu Spectrophotometer UV-1900). Furthermore, for the Surface Plasmon Resonance (SPR) system application, SPR analysis was conducted using the Bruker Sierra SPR-32 system, acknowledged for its exceptional performance in Surface Plasmon Resonance, as highlighted at SLAS Europe 2018. The thickness of the resultant PVC@Ag film was measured using Digital Micrometer film 4000DIG model.

3 Results and Discussions

3.1 Investigation and Examination of the Fabricated PVC@Ag Nanocomposite

The structural analysis of both the PVC polymer and the PVC@Ag nanocomposite involved an extensive examination using X-ray diffraction (XRD) technique to investigate their composition and characteristics. Specifically, the PVC@Ag nanocomposite was studied at varying concentrations of Ag nanoparticles, spanning from 1 to 4%, utilizing XRD analysis. The XRD spectra provided insights into the crystalline nature of both the pristine PVC and the PVC@Ag nanocomposite, visually depicted in Fig. 1. Examination of the XRD patterns associated with the silver nanoparticles showcased distinctive peaks located at 2θ = 38°, 44°, 64°, and 78°, corresponding to the (111), (200), (220), and (311) crystallographic planes, confirming the face-centered cubic crystalline arrangement of the Ag nanoparticles [49]. Illustrated in Fig. 1(A), the XRD patterns depicted the amorphous state of the pure PVC polymer, indicating a broad peak around a 2θ value of approximately 20°, affirming the polymer's amorphous nature without definitive peak spectra [50]. Introducing varying concentrations of Ag nanoparticles within the PVC matrix displayed evident alterations in crystalline structure. Figures 1 (B, C, D, and E) portrayed a noticeable shift in the structural configuration of the PVC@Ag nanocomposite upon the integration of silver nanoparticles. This analysis indicated a transition from a semi-crystalline to a more crystalline state in these PVC@Ag nanocomposite samples, as visually represented in Fig. 1. Specifically, the XRD patterns of the PVC@Ag nanocomposite exhibited four distinct peaks attributed to the presence of silver, signifying a progression towards a crystalline structure. Furthermore, an observable enhancement in peak intensity was evident in the XRD pattern of the PVC@Ag nanocomposite, corresponding to increased concentrations of Ag nanoparticles.

Fig. 1
figure 1

X-ray diffraction patterns demonstrating (A) the pure PVC and different compositions of PVC@Ag nanocomposite denoted as (B) 1%, (C) 2%, (D) 3%, and (E) 4% incorporating Ag nanoparticles

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The expansion in XRD line widths was observed to be influenced by the particle size, suggesting that the materials exhibited properties at the nanocrystalline level and indicative of particle sizes existing within the nanometer range [51]. The integration of silver nanoparticles into the PVC matrix notably transformed the structure of the PVC@Ag nanocomposite. Changes in the concentration of silver nanoparticles visibly impacted the intensity of peaks corresponding to the (111), (200), (220), and (311) planes. To analyze these variations, an estimation of crystallite size was conducted using Scherrer's equation [52].

$$D= \frac{0.9\lambda }{\beta cos\theta }$$
(1)

Here, β denotes the full width at half maximum (FWHM) of the XRD peak observed at the diffraction angle θ. The average sizes of crystallites within the PVC@Ag samples are detailed in Table 1. Fluctuations in the concentrations of Ag nanoparticles resulted in varying adjustments in crystallite sizes. This variability enables the determination of average dislocation density (δ), which represents either the total dislocation length within a material's unit volume or the count of dislocations intersecting a unit area of a random section. The material's strength, influenced by its dislocation density (δ), correlates with changes in strain (ε) associated with alterations in plane spacings. The measurement of strain provides valuable insights into material stress levels. Equations (2 and 3) [53,54,55,56] presented methodologies for estimating strain and dislocation density.

Table 1 The Average Crystalline Size, Strain, and Dislocation Density of the Investigated PVC@Ag Nanocomposite
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$$\delta = \frac{n}{{D}^{2}}$$
(2)
$$\varepsilon = \frac{\beta cos\theta }{4}$$
(3)

When the parameter 'n' is set to unity, it signifies a minimal dislocation density. Table 1 data details the dislocation density (δ) and strain (ε) values related to the (111), (200), (220), and (311) planes in the PVC@Ag samples. Employing atomic force microscopy (AFM), the morphology of the PVC@Ag nanocomposite was examined. Through image analysis, the particle size was determined. AFM, although an indirect method, was allowed for a comprehensive exploration of the size, shape, and crystalline characteristics of the PVC@Ag nanocomposite. Figure (2A) showcases AFM images displaying the nanocomposite at various concentrations of silver nanoparticles. Altering the concentrations of silver nanoparticles within the PVC matrix (from 1 to 4%) resulted in visible morphological changes in the nanocomposite. The size decreased from 75 nm (4% concentration) to 65 nm (3% concentration) and further reduced to 55 nm (2% concentration), and eventually to 48.5 nm (1% concentration). Notably, most nanocomposites displayed a tendency for nanoparticle aggregation on the polymer surface, attributed to their increased surface area and concentration [57]. In Fig. (3B), the AFM histogram showed that the particle size has been increased due to increasing the concentration of silver nanoparticles. The AFM analysis indicated that the silver nanoparticles within the PVC@Ag nanocomposite were primarily polydisperse, with some exhibiting an aggregated nature. This tendency for aggregation could be related to the encapsulation of Ag nanoparticles by PVC molecules, resulting in multilayer formation through interactions with adjacent molecules. The covalent binding of PVC to Ag nanoparticles might trigger specific or nonspecific reactions, promoting nanoparticle aggregation by attracting additional molecules [58].

Fig. 2
figure 2

A Atomic force microscope (AFM) images showcasing the PVC@Ag nanocomposite samples at diverse concentrations of silver nanoparticles: (A-B) 4%, (C-D) 3%, (E–F) 2%, and (G-H) 1%

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Fig. 3
figure 3

B Atomic force microscope (AFM) histogram visuals showcasing the PVC@Ag nanocomposite samples at diverse concentrations of silver nanoparticles: (A) 1%, (B) 2%, (C) 3%, and (D) 4%

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The atomic force microscope (AFM) images revealed crystal sizes larger than those observed in XRD data, primarily due to nanoparticle aggregation. To comprehensively examine the structure, scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed. SEM analysis disclosed grains uniformly spread across the sample surface, with various Ag nanoparticle clusters dispersed randomly. Illustrated in Fig. 4, the depiction revealed the dispersed yet randomly distributed Ag nanoparticles within the PVC material, suggesting consistent structure and the formation of small clusters [59].

Fig. 4
figure 4

SEM micrographs depict the PVC@Ag nanocomposite at varying concentrations: (A) 1%, (B) 2%, (C) 3%, and (D) 4%

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SEM observations corroborated irregular particle sizes and shapes, in line with AFM findings. Surface morphology examination, represented in Fig. 4 (A, B, C, and D), highlighted the uneven size distribution of Ag nanoparticles. Nevertheless, SEM micrographs displayed a homogeneous dispersion of silver nanoparticles within the PVC matrix [60].

Analysis indicated a smooth surface at Ag nanoparticle concentrations up to 2% but roughened at 4%. This alteration may resulted from the interactions between Ag nanoparticles and PVC chains, linking them to the PVC matrix, potentially causing surface aggregation in the PVC composite. Employing TEM to scrutinize the nano-scale structure and morphology of the PVC@Ag nanocomposite confirmed the integration of Ag nanoparticles within the PVC matrix. As depicted in Fig. 5, TEM images exhibited uniformly spherical silver nanoparticles in the PVC@Ag nanocomposite, displaying variability in nanoparticle size [57] (Table 2).

Fig. 5
figure 5

TEM imaging displays the PVC@Ag nanocomposite at different concentrations: (A) 1%, (B) 2%, (C) 3%, and (D) 4%

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Table 2 The Energy Dispersive X-Ray Analysis (EDAX) Composition of PVC Embedded with Silver Nanoparticles at Concentrations of 1%, 2%, 3%, and 4%
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Surface area, pore size, and pore volume were assessed using BET analysis, detailed in Table 3. The surface area of PVC@Ag samples at 1% Ag nanoparticle concentration measured to be 30.09 m2/g. As the loading of silver nanoparticles increased, these nanosilver structures filled the PVC pores, resulting in a decline in surface area to 27.08 m2/g. This trend persisted with the rise in silver nanoparticle concentration, leading to a decrease in surface area to 25.27 m2/g at 3%. However, at a concentration of 4%, the surface area marginally increased to 54.16 m2/g. These observations underscore the compact arrangement of silver nanoparticles on PVC surfaces, leveraging their diminutive size to maximize surface area and dispersion [58].

Table 3 The N2 Adsorption–Desorption Isotherm for the Fabricated PVC@Ag Samples
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Furthermore, the International Union of Pure and Applied Chemistry (IUPAC) classified porous solid materials based on pore sizes: macroporous (> 50.0 nm), mesoporous (2.0–50.0 nm), and microporous (up to 2.0 nm) [59]. The PVC@Ag nanocomposite demonstrated mesoporous characteristics, evident from its pore size falling within the 2.0–50.0 nm range.

Dynamic Light Scattering (DLS) analysis was employed to determine the average particle size and size distribution of silver nanoparticles within the PVC@Ag nanocomposite. This method has the capability to assess the size distribution of particles suspended in solutions, covering sizes ranging from submicron to one nanometer [61]. Utilizing the interaction of light with particles, dynamic light scattering delivers precise measurements of narrow particle size distributions, particularly within the 2–500 nm range [61].

As indicated in Fig. 6, the PVC@Ag nanocomposite displayed average particle sizes of 32 nm, 37 nm, 43 nm, and 24 nm for concentrations of 1%, 2%, 3%, and 4%, respectively. These observations confirmed that the nanoparticles fall within the nano range. Zeta potential analysis was employed to ascertain the surface charge of the PVC@Ag nanocomposite, providing significant insights into nanoparticle stability [62]. The zeta potential served as an indicator of nanoparticle dispersion and surface charge [62]. As depicted in Fig. 7, distinct peaks were identified at approximately -30, -34, -24, and -40 mV for PVC@Ag samples at concentrations of 1%, 2%, 3%, and 4%, respectively. It is commonly acknowledged that colloidal stability is achieved when zeta potentials approach -30 mV [63, 64]. The nanocomposite demonstrated a relative stability in colloidal solutions, evident from its negative zeta potential, which ranged between ≤ -30 mV and ≥  + 30 mV. Anionic nanoparticles typically exhibit zeta potentials below -30 mV. The negative zeta potential ensured the initial dispersion of Ag nanoparticles in the colloidal solution, while also suggesting the possibility of eventual nanoparticle aggregation due to the weak repulsive forces between nanoparticles [65].

Fig. 6
figure 6

Showcases the outcomes acquired through Dynamic Light Scattering (DLS) analysis

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Fig. 7
figure 7

The provided zeta potential data

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4 Investigations Regarding Surface Plasmon Resonance (SPR) on the PVC@Ag Nanocomposite

The depiction in Fig. 8 illustrated the process initiated by the interaction of a monochromatic light beam with a metal surface, initiating the surface plasmon resonance (SPR) as a quantum electromagnetic event. The emergence of SPR occurred due to the interaction between light and electrons at the boundary of a metal and dielectric medium, representing a quantum electromagnetic phenomenon [66]. Displayed in Fig. 8 is the occurrence that takes place when a monochromatic light beam interacts with a metal surface. SPR arises from the intertwining of light and electrons at the interface between the metal and dielectric medium, constituting a quantum electromagnetic process.

Fig. 8
figure 8

The experimental arrangement for surface plasmons [66]

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When light meets the requirements for resonance and its frequency coincides with that of the surface plasmon wave, light can partially transmit its energy to the electrons on the metallic surface at a particular angle of incidence. There is a decrease in the intensity of the reflected light. Surface plasmons (SPs) are electron-consistent oscillations that travel parallel to a metallic surface and were triggered by an exponentially declining input light field. Resonance angle, or SPR drop, is the angle at which the reflected light exhibits a tiny degree of intensity [66]. SPR is a distinguished technique to observe modification taking place in the intensity proximity of the surface of the metal. When molecules adsorbed on the metal surface, the resonance spectral response of the SPR will change in intensity. This will cause an angular shift or drop in SPR spectral position, which will reflect specific system characteristics and provide information about the molecules that have been adsorbed on the surface [66].

In this study, PVC@Ag nanocomposites with different percentage of silver nanoparticles, based on the SPR, were used to detect the cadmium ions. Choosing the metallic layer is essential for detecting high sensor sensitivity. Utilization of gold thin film is generally employed due to its stability [67]. Silver suffers from oxidation, which limits some of its SPR performance. Figure (9) showed the SPR reflectance curve for the PVC@Ag nanocomposite samples. The SPR intensity of PVC@Ag nanocomposite is represented in Fig. 9. Firstly, SPR gave specific peak with certain angle of incidence (θ) which is due to gold thin film and PVC@Ag nanocomposite sample (as blank). When the Cd(II) ion pollutant is added on PVC@Ag nanocomposite sample, it adsorbed on the surface of the nanocomposite sample causing shift in the angle of incidence. Therefore, the change of angle of incidence can be attributed to the Cd(II) ion pollutant adsorbed on the surface. The PVC@Ag nanocomposite samples covered the gold (Au) surface acted as the active sensing layer for Cd(II) detection. Therefore, a shift in the SPR angle when the light interacted with PVC@Ag nanocomposite after and before Cd(II) ion adsorption is produced. By eliminating the blank peak, thus the obtained peaks are only accounted for the angle of incidence of adsorption of a Cd(II) ion pollutant because the angle of incidence (θ) of thin film and nanocomposite samples is eliminated. Thus, the angle of incidence (θ) of adsorption of Cd(II) ion on the surface of PVC@Ag nanocomposite samples and the corresponding intensities was represented in Fig. (10). It is obvious from this figure that the angle of incidence (θ) was 26.30° and the intensity values obtained were 11.13, 12.06, 12.19 and 10.80 for 1%, 2%, 3% and 4% nanocomposites samples, respectively. The variation in intensity of light which resulted from the reflectance of the nanocomposite samples that reacted with Cd(II) ions and this change is recorded by the SPR detector. A small dip was noticed for SPR plots using standard Cd(II) ion solution. It can deduce that SPR method depended on PVC@Ag nanocomposite samples which are credible for Cd(II) ion detection. The surface plasmon resonance (SPR) technique exploits the unique optical properties arising from the collective oscillation of conduction electrons at the interface between a metal and a dielectric medium. In this study, the PVC@Ag nanocomposite served as the active sensing layer on a gold thin film, facilitating the label-free detection of cadmium(II) ions in aqueous solutions. Upon exposure to Cd(II) ions, the nanocomposite's surface undergoes specific interactions and adsorption phenomena, altering the local refractive index at the metal–dielectric interface. This refractive index change is transduced into a measurable shift in the SPR angle and intensity, enabling quantitative detection of the Cd(II) analyte.

Fig. 9
figure 9

The surface plasmon resonance patterns representing the PVC@Ag nanocomposite at different concentrations: (A) 1%, (B) 2%, (C) 3%, and (D) 4%

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Fig. 10
figure 10

The Raman spectroscopy illustrates the compositional characteristics of the PVC@silver nanocomposite at various concentration levels (1%, 2%, 3%, and 4%)

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The adsorption mechanism is governed by the high affinity of Cd(II) ions towards the silver nanoparticles embedded in the PVC matrix. The nanoparticles' large surface-to-volume ratio and their plasmonic properties contribute to enhanced binding kinetics and sensitivity. Additionally, the polymeric PVC host offers functional moieties (e.g., chloride groups) that can participate in selective complexation with Cd(II) ions through electrostatic interactions or chelation. However, the adsorption process can be tailored by optimizing parameters such as pH, ionic strength, and temperature to enhance the selectivity and sensitivity towards Cd(II) ion over competing metal ions. Surface functionalization strategies, involving the incorporation of specific ligands or molecular recognition elements, could further augment the nanocomposite's affinity and selectivity for Cd(II) detection. Post-sensing regeneration and reusability of the PVC@Ag nanocomposite can be achieved through desorption protocols, employing appropriate eluents or chelating agents to disrupt the Cd(II) ion-nanocomposite interactions. This approach enables the recovery and recycling of the sensing platform, minimizing operational costs and environmental impact. Kinetic studies and adsorption isotherm modeling can provide insights into the adsorption mechanisms, binding affinities, and maximum Cd(II) ion removal capacities, facilitating the design and optimization of the PVC@Ag nanocomposite for practical water treatment applications.

The SPR angle, marked by a significant intensity decline, holds considerable importance. A sharper SPR dip is preferred due to its heightened sensitivity derived from a deeper curve and increased detection accuracy resulting from a narrower width. Sensor parameters, notably the choice of metals, exert a substantial influence on the width and depth of the SPR dip, impacting detection efficiency [68].

For the validation of inherent morphological structures within the PVC@Ag nanocomposite, Raman scattering spectroscopy was utilized. Figure 10 portrays the Raman spectrum, illustrating the vibrational characteristics of the nanocomposite. Key Raman lines assigned to the PVC@Ag nanocomposite are presented in Fig. 10. These spectral attributes were identified in regions associated with C–Cl, C-H, and CH2 stretching vibrations, revealing specific frequencies: 361 cm−1 for C–Cl in trans HClC = CHCl in-plane bending mode; 636–695 cm−1 for C–Cl stretching vibration; 1102–1179 cm−1 for C–C stretching; 1334–1403 cm−1 for C–H symmetrical stretching in CH2 group; 2916 cm−1 for C–H asymmetrical stretching in CH2 group; and 2975 cm−1 for C–H asymmetrical stretching in CH3 group [69]. Significant PVC peaks were identified in the spectral range of C-H and CH2 stretching vibrations in the region of 2750–3100 cm−1. The vibrations associated with C–Cl in PVC were detected at 694 and 635 cm−1, while the presence of alkyl (CHn) was identified at 1431 cm−1 [70]. A subtle deviation observed in the characteristic bands of PVC implies an interaction between the Ag nanoparticles and the PVC polymer, as depicted in Fig. 10.

The absorbtion spectra of the PVC@Ag nanocomposites were plotted across a range of Ag nanoparticle concentrations from 190 to 1100 nm, as presented in Fig. 11. Variations in the quantity of silver profoundly impact absorbance, revealing a decline with increasing wavelengths. Figure 11 delineated distinct surface plasmon resonance bands observed within the PVC@Ag nanocomposite at 420–430 nm, confirming the successful integration of silver nanoparticles in the PVC matrix. The observed spectra demonstrated heightened absorbance in the ultraviolet region and relatively lower absorbance in the visible region, indicating interactions between incident photons and the material, particularly as wavelengths decrease [71]. Moreover, the absorbance increased as the nanoparticle weight escalates, attributed to incident light absorption by unbound electrons [71]. For quantitative analysis, the optical absorption coefficient α is calculated (Eq. 4) [72]:

Fig. 11
figure 11

The graphical representation showcases the correlation between absorbance and wavelength for the PVC@Ag nanocomposite across different concentrations: 1%, 2%, 3%, and 4%

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$$\mathrm{\alpha }=2.303\,\mathrm{ A }/\mathrm{ t}$$
(4)

The computation of the optical absorption coefficient (α) involves parameters such as 'A' for absorbance and 't' denoting the thickness of the specimen. Figure (12) illustrated the nanocomposite's wavelength variation alongside coefficient of absorption (α). The analysis revealed that α demonstrated its minimum value at elevated wavelengths, suggesting a scarcity of electron transitions due to insufficient energy from incident photons to facilitate movement from the valence band to the conduction band (hυ < Eg). Conversely, an increase in energy resulted in a rise in the absorption coefficient [73]. The existence of viable electron transitions stems from the potent absorption at shorter wavelengths. Consequently, the photon's energy surpasses the energy gap, enabling the transition from the valence band to the conduction band. This underscores how the absorption coefficient serves as a gauge for determining electron transition types: heightened absorption coefficients at shorter wavelengths imply a likelihood of direct transitions, while lower coefficients at longer wavelengths indicate the likelihood of indirect transitions [71].

Fig. 12
figure 12

The association between the absorption coefficient and the wavelength of the PVC@Ag nanocomposite across various concentrations: 1%, 2%, 3%, and 4%

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The energy gap, a significant parameter, signifies the minimum energy difference between the highest valence band and the lowest conduction band [74]. Within PVC, the magnitude of the mobility gap depends on factors like conditions, material type, and impurity concentration. Alterations in these factors can result in shifts in the absorption edge toward higher or lower energy ranges [74]. The connection between incident photon energy (hυ) and (αhυ)2 is presented in Fig. 13, facilitating the calculation of the optical band gap (Eq. 5) [75]:

Fig. 13
figure 13

The correlation between the energy gap of allowed direct transitions [(αhυ)2] and the photon energy in the PVC@Ag nanocomposite across different concentrations: 1%, 2%, 3%, and 4%, is depicted

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$$\alpha h\nu =B{(h\nu -{E}_{g})}^{n}$$

The formula outlines the calculation of the optical band gap (Eg) for PVC@Ag nanocomposite samples, where 'B' stands for an energy-independent constant, and 'n' signifies the type of transitions, where 'n = 2' represents indirect allowed transitions and 'n = ½' denotes direct allowed transitions. The computed Eg values approximate to 4.51 eV for 1%, 4.33 eV for 2%, 4.27 eV for 3%, and 4.12 eV for 4% concentrations. For indirect allowed transition the computed energy gap (Eg) value approximates to 2.63 eV for 1%, 2.52 eV for 2%, 2.27 eV for 3%, 1.91 eV for 4% (Fig. 14).

Fig. 14
figure 14

The correlation between the energy gap of allowed indirect transitions [(αhυ)0.5] and the photon energy in the PVC@Ag nanocomposite across different concentrations: 1%, 2%, 3%, and 4%

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5 Conclusions

This study successfully demonstrated the development and characterization of a novel PVC@Silver nanocomposite material for highly sensitive detection of cadmium(II) ions in water samples. The systematic incorporation of silver nanoparticles (1–4% w/w) into the PVC matrix resulted in significant alterations in the structural, morphological, and optical properties of the nanocomposite, as evidenced by complementary analytical techniques. X-ray diffraction analysis confirmed the face-centered cubic crystalline structure of the embedded silver nanoparticles, with average crystallite sizes ranging from 26.1 nm (3% Ag) to 30.0 nm (2% Ag). Dynamic light scattering measurements revealed nanoparticle sizes between 24–43 nm, while zeta potential values (-24 to -40 mV) indicated reasonable colloidal stability. Notably, the PVC@Silver nanocomposite exhibited exceptional performance in cadmium(II) ion detection using surface plasmon resonance (SPR) spectroscopy. The SPR response demonstrated a significant angular shift of 26.30° and intensity variations from 10.80 (4% Ag) to 12.19 (3% Ag), attributed to the adsorption of cadmium(II) ions on the nanocomposite's surface. This concentration-dependent response highlights the crucial role of silver nanoparticle loading in modulating the sensing capabilities. UV–vis spectroscopy revealed a prominent surface plasmon resonance band at 420–430 nm, confirming the presence of silver nanoparticles within the PVC matrix. Furthermore, the optical band gap of the nanocomposite could be tuned from 4.51 eV (1% Ag) to 4.12 eV (4% Ag) by varying the silver nanoparticle concentration. The synergistic combination of the robust PVC polymer host and the plasmonic properties of silver nanoparticles endowed the PVC@Silver nanocomposite with exceptional sensing performance for cadmium ion detection. These findings pave the way for the development of cost-effective and sensitive sensor platforms for monitoring heavy metal contamination in environmental and drinking water samples.