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Herein, we demonstrate the effectiveness of surface-enhanced Raman scattering (SERS) to detect trace concentration of potentially harmful imidacloprid pesticide. To achieve this ultimate objective, a rapid and highly effective methodology for the fabrication of active and stable porous silicon (PSi) plated palladium nanoparticles (PdNPs) SERS substrates by an electrochemical anodization and immersion plating routes was applied. The PSi layers were fabricated by the electrochemical anodization of a silicon wafer in ethanoic fluoride solution, followed by uniformly deposition of PdNPs via a simple immersion plating technique. The structural features and morphology of fabricated frameworks of PSi-Pd NPs have been investigated by field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectra. The PSi substrate demonstrates a meso-porous morphology with good distribution, good pore density and average pore sizes around 20 nm. The SERS performance of Si–Pd NPs and PSi–Pd NPs substrates has been examined taking imidacloprid (an insecticide) as a target analyte. The SERS signal of imidacloprid using PSi–Pd NPs substrate exhibited immense enhancement compared to the Si-Pd NPs substrate. The active substrate revealed excellent detectable performance with a concentration as low as 10–9 M imidacloprid and an enhancement factor (EF) of 1.2 × 105. This large EF is fundamentally ascribed to the combined effect of the electromagnetic improvement and charge transfer mechanisms. Additionally, no aging effect was observed for the present substrates kept in air for two weeks. Striking enhancement in Raman spectral signals obtained with the current PSi–Pd NPs substrates can provide a simple and smooth platform towards the sensitive detection of various target analytes.

Glasses of the composition 37.5Li2O-25V2O5-37.5P2O5 mol% containing different sulfur (0, 10, 50, 100 mol%) content were successfully synthesized and investigated as electrodes for electrochemical devices. Both galvanostatic charge/discharge (GCD) and cyclic voltammetry (CV) were performed to study of electrochemical properties. The results showed that glasses containing sulfur (S) exhibited a high performance, such as specific capacitance, energy density and power density, compared with the S-free glass. These properties increased with increasing of S content. The outstanding electrochemical performance of the glasses containing S can be attributed to the partial substitution of oxygen (O) atoms by S atoms. Since the radius of S ion is higher than O ion, this substitution can significantly enlarge the size of Li-ion transfer pathway. Besides, S ion has better polarization ability than O ion, thus weakens the interaction between Li ions and glass network. Therefore, the addition of S into oxide glasses may be an effective way to improve the performance of electrochemical devices electrodes.

The glasses defined by the formula 37.5Li2O–25V2O5–37.5P2O5 mol% containing different sulfur (0, 10, 50 and 100 mol%) content were studied before and after nanocrystallization. X-ray diffraction and transmission electron micrograph of the heat treated samples indicated nanocrystals embedded in the glass matrix. The average crystallite size was found between 18 and 37 nm. Sulfur (S) behaved as a reducing agent for redox reaction during preparation of glass and affected the conductivity, i.e., the V4+–V5+ or V3+–V4+ion pairs increased with increasing S content and led to increasing conductivity of glasses. After creation of the nanocrystalline phase, S-free glass–ceramic nanocomposite exhibited improvement in electrical conductivity around three orders of magnitude than initial glass. This great improvement of electrical conductivity is related to increase in a concentration of V4+–V5+or V3+–V4+ ion pairs and also, forming of defective and well-conducting regions along the crystallite/glass interfaces. The decrease in electrical conductivity in the 50S glass–ceramic nanocomposite, which possessed the highest crystallite size, could be related to the increase of grain boundaries scattering because of the increasing crystallite size. The conduction was attributed to non-adiabatic small polaron hopping and mostly determined by hopping carrier mobility.

Li3V2(PO4)3 glass-ceramic nanocomposites, based on 37.5Li2O-25V2O5-37.5P2O5 mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li3V2(PO4)3 NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li+ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li+ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li+ ions/electrons and higher surface area of contact between cathode and electrolyte.

The novel Li3V2(PO4)3 glass-ceramic nanocomposites were synthesized and investigated as electrodes for energy storage devices. They were fabricated by heat treatment (HT) of 37.5Li2O–25V2O5–37.5P2O5 mol% glass at 450 °C for different times in the air. XRD, SEM, and electrochemical methods were used to study the effect of HT time on the nanostructure and electrochemical performance for Li3V2(PO4)3 glass-ceramic nanocomposites electrodes. XRD patterns showed forming Li3V2(PO4)3 NASICON type with monoclinic structure. The crystalline sizes were found to be in the range of 32–56 nm. SEM morphologies exhibited non-uniform grains and changed with variation of HT time. The electrochemical performance of Li3V2(PO4)3 glass-ceramic nanocomposites was investigated by using galvanostatic charge/discharge methods, cyclic voltammetry, and electrochemical impedance spectroscopy in 1 M H2SO4 aqueous electrolyte. The glass-ceramic nanocomposites annealed for 4 h, which had a lower crystalline size, exhibited the best electrochemical performance with a specific capacity of 116.4 F g−1 at 0.5 A g−1. Small crystalline size supported the lithium ion mobility in the electrode by decreasing the ion diffusion pathway. Therefore, the Li3V2(PO4)3 glass-ceramic nanocomposites can be promising candidates for large-scale industrial applications in high-performance energy storage devices.

The effect of grain size on the structural and transport properties of glass–ceramic nanocomposites consisting of Li3V2(PO4)3 crystals were investigated by differential scanning calorimeter, X-ray diffraction (XRD), transmission electron micrograph (TEM), density (d) and dc conductivity. XRD patterns exhibit the formation of Li3V2(PO4)3 with monoclinic structure. It was shown by XRD and TEM studies that by appropriate heat-treatment glasses can be turned into glass–ceramic nanocomposites consisting of crystallites smaller than 56 nm embedded in the glassy matrix. Density was found to increase with increasing grain size while the molar volume decreases. The dc conductivity measured in high temperature range increased with decreasing of the grain size while the activation energy decreased. The calculated dc conductivity at 400 K for the present glass was 5.77 × 10−7 S/cm, while in its glass–ceramic nanocomposites was in the range of 1.712 × 10−5–2.10 × 10−6 S/cm. On the other hand, the calculated activation energy for the present glass was 0.542 eV, while in its glass–ceramic nanocomposites was in the range of 0.165–0.468 eV. The increase in electrical conductivity in the glass–ceramic nanocomposite annealed at 450 °C for 4 h compared to that annealed at 450 °C for 2, 8, 24 h can be attributed to the decrease in grain boundary scattering due to the reduction in grain size. The conduction was confirmed to obey non-adiabatic small polaron hopping. The electron–phonon interaction coefficient (γ p) was calculated and found to be in the range of 5.09–16.64.