Vanillic Acid Nanocomposite: Synthesis, Characterization Analysis, Antimicrobial, and Anticancer Potentials

Recently, nanoparticles have received considerable attention owing to their efficiency in overcoming the limitations of traditional chemotherapeutic drugs. In our study, we synthesized a vanillic acid nanocomposite using both chitosan and silver nanoparticles, tested its efficacy against lung cancer cells, and analyzed its antimicrobial effects. We used several characterization techniques such as ultraviolet-visible spectroscopy (UV-Vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDAX), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to determine the stability, morphological characteristics, and properties of the biosynthesized vanillic acid nanocomposites. Furthermore, the vanillic acid nanocomposites were tested for their antimicrobial effects against Escherichia coli and Staphylococcus aureus, and Candida albicans. The data showed that the nanocomposite effectively inhibited microbes, but its efficacy was less than that of the individual silver and chitosan nanoparticles. Moreover, the vanillic acid nanocomposite exhibited anticancer effects by increasing the expression of pro-apoptotic proteins (BAX, Casp3, Casp7, cyt C, and p53) and decreasing the gene expression of Bcl-2. Overall, vanillic acid nanocomposites possess promising potential against microbes, exhibit anticancer effects, and can be effectively used for treating diseases such as cancers and infectious diseases.

Enhanced visible-light photodegradation of fluoroquinolone-based antibiotics and E. coli growth inhibition using Ag-TiO2 nanoparticles

Antibiotics in wastewater represent a growing and worrying menace for environmental and human health fostering the spread of antimicrobial resistance. Titanium dioxide (TiO₂) is a well-studied and well-performing photocatalyst for wastewater treatment. However, it presents drawbacks linked with the high energy needed for its activation and the fast electron–hole pair recombination. In this work, TiO₂ nanoparticles were decorated with Ag nanoparticles by a facile photochemical reduction method to obtain an increased photocatalytic response under visible light. Although similar materials have been reported, we advanced this field by performing a study of the photocatalytic mechanism for Ag–TiO₂ nanoparticles (Ag–TiO₂ NPs) under visible light taking in consideration also the rutile phase of the TiO₂ nanoparticles. Moreover, we examined the Ag–TiO₂ NPs photocatalytic performance against two antibiotics from the same family. The obtained Ag–TiO₂ NPs were fully characterised. The results showed that Ag NPs (average size: 23.9 ± 18.3 nm) were homogeneously dispersed on the TiO₂ surface and the photo-response of the Ag–TiO₂ NPs was greatly enhanced in the visible light region when compared to TiO₂ P25. Hence, the obtained Ag–TiO₂ NPs showed excellent photocatalytic degradation efficiency towards the two fluoroquinolone-based antibiotics ciprofloxacin (92%) and norfloxacin (94%) after 240 min of visible light irradiation, demonstrating a possible application of these particles in wastewater treatment. In addition, it was also proved that, after five Ag–TiO₂ NPs re-utilisations in consecutive ciprofloxacin photodegradation reactions, only a photocatalytic efficiency drop of 8% was observed. Scavengers experiments demonstrated that the photocatalytic mechanism of ciprofloxacin degradation in the presence of Ag–TiO₂ NPs is mainly driven by holes and ˙OH radicals, and that the rutile phase in the system plays a crucial role. Finally, Ag–TiO₂ NPs showed also antibacterial activity towards Escherichia coli (E. coli) opening the avenue for a possible use of this material in hospital wastewater treatment.

Ag nanoparticles decorated-TiO₂ P25 are a viable alternative for the degradation, through a rutile-mediated mechanism, of fluoroquinolone-based antibiotics under visible light irradiation and, at the same time, for bacteria inactivation in water.

Dependence of the electrical properties of Cu-doped ZnO nanoparticles decorated by Ag atoms

Silver decorated copper doped zinc oxide nanoparticles (Ag@Cu-ZnO) were successfully prepared via sol gel method. X-ray diffraction analysis revealed ZnO wurtzite crystalline structure with the existence of minor peaks attributed to Cu and Ag. The presence of Cu and Ag in addition to ZnO lattice was supplementary verified by EDS data while the shift in the FTIR band confirmed the Cu incorporation within the ZnO host lattice. Both SEM and XRD revealed an increase in particle size with Ag loading. At different frequencies, electrical measurements demonstrated a decrement in the dielectric constant, dielectric loss and AC conductivity with the increment of Ag content. Meanwhile, the Nyquist plots of the impedance measurement showed a single semicircle arc indicating the predominance of grain boundary resistance. This study elucidated the great influence of Ag on Cu-doped ZnO nanoparticles’ structural, dielectric constant and electrical conductivity which make it a promising candidate for catalytic, photocatalytic and adsorption applications.

Dependence of the electrical properties of Cu-doped ZnO nanoparticles decorated by Ag atoms

Silver decorated copper doped zinc oxide nanoparticles (Ag@Cu-ZnO) were successfully prepared via sol gel method. X-ray diffraction analysis revealed ZnO wurtzite crystalline structure with the existence of minor peaks attributed to Cu and Ag. The presence of Cu and Ag in addition to ZnO lattice was supplementary verified by EDS data while the shift in the FTIR band confirmed the Cu incorporation within the ZnO host lattice. Both SEM and XRD revealed an increase in particle size with Ag loading. At different frequencies, electrical measurements demonstrated a decrement in the dielectric constant, dielectric loss and AC conductivity with the increment of Ag content. Meanwhile, the Nyquist plots of the impedance measurement showed a single semicircle arc indicating the predominance of grain boundary resistance. This study elucidated the great influence of Ag on Cu-doped ZnO nanoparticles’ structural, dielectric constant and electrical conductivity which make it a promising candidate for catalytic, photocatalytic and adsorption applications.

Synthesis of Ag/TiO2 nanocomposite via plasma liquid interactions: Improved performance as photoanode in dye-sensitized solar cell

Ag/TiO₂ nanocomposite was prepared by the atmospheric direct current plasma in aqueous solution to improve its performance in dye-sensitized solar cells (DSSCs) as the photoanode. The fabricated DSSC shows high power conversion efficiency over 6.5% and displays better long-term stability than that of referenced pure TiO₂. The comparison of photoluminescence spectra of Ag/TiO₂ and pure TiO₂ showed that only the Ag containing samples had notable photocurrent under visible light, which was attributed to the highly dispersed Ag, according to the EDS and XRD measurements. The short-circuit current density (Jsc) and open-circuit voltage (Voc) reached 13.43 mA cm^-2 and 0.72 V in Ag/TiO₂, and 9.44 mA cm^-2 and 0.68 V in pure TiO₂, respectively. The performance improvement in Ag/TiO₂ DSSC may occur due to the declined band-gap energy, retarded charge recombination and greater surface coverage of the sensitizing dye over Ag/TiO₂ nanocomposite.

Enhanced Photocatalytic Efficiency of a Least Active Ag-TiO2 by Amine Adsorption

An Ag-TiO2 photocatalyst with 3.5 atom % silver content, synthesized by a single step sol-gel method, possessed silver nanoparticles (AgNPs; 1-5 nm) on the TiO2 surface, but owing to the nonplasmonic nature of AgNPs and the wide band gap of TiO2, this material exhibited poor activity in a photocatalytic degradation reaction. However, this least active Ag-TiO2 catalyst showed a sudden increase in activity during a photocatalytic amine self-coupling reaction showing the highest activity, which was interpreted as amine (reactant) adsorption-driven activity enhancement. We found that amine adsorption occurred over AgNPs converting into plasmonic AgNPs as well as on the TiO2 surface reducing the band gap and therefore facilitated the visible light excitation and the electron-transfer process efficiently, resulting into overall enhancement in the photocatalytic activity. Thus, a very efficient, stable, and visible light active photocatalyst (amine-adsorbed Ag-TiO2) was developed by simply adsorbing an amine in the least active Ag-TiO2 photocatalyst.

Surface Alloying in Silver-Cobalt through a Second Wave Solution Combustion Synthesis Technique

Herein, we report the synthesis of silver-cobalt nanopowders using three different modes of solution combustion synthesis, and we present the effects of the synthesis conditions on particle morphology. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectrophotometer (UV-vis), Transmission electron microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS) to understand the structural and elemental properties. When Co is synthesized over Ag in a second wave of combustion, peak shifts observed in XRD and XPS show a change in the cell parameters and prove the existence of a strong electronic interaction between Ag and Co. Better control of mixing and alloying through the second wave combustion synthesis mode (SWCS) was evident. The sequence of combustion affects the structure and composition of the material. SWCS reduces the amount of carbon content, as compared to single-stage combustion, and the combustion of carbon is followed by a rearrangement of atoms.

Photosensitization of TiO2 nanofibers by Ag2S with the synergistic effect of excess surface Ti3+ states for enhanced photocatalytic activity under simulated sunlight

TiO₂ nanofibers, with mean diameter ~200 nm, were fabricated by electrospinning and successfully photosensitized with low bandgap Ag₂S nanoparticles of 11, 17, 23 and 40 nm mean sizes, with corresponding loading of 4, 10, 18 and 29 wt.% Ag₂S, respectively. 17 nm Ag₂S@TiO₂ nanofibers exhibited optimal activity in the photodegradation of methylene blue under simulated sunlight with pseudo-first order rate constant of 0.019 min⁻¹ compared to 0.009 min⁻¹ for pure TiO₂ nanofibers. In spite of greater visible-light absorption and reduced bandgap, larger than 17 nm Ag₂S nanoparticles exhibited sluggish photodegradation kinetics probably due to less photo-induced carriers generation in TiO₂ and reduced electron injection rates from the larger sized Ag₂S into TiO₂. Furthermore, a UV-O₃ surface treatment induced excess Ti³⁺ surface states and oxygen vacancies which synergistically enhanced the photodegradation rate constant to 0.030 min⁻¹ for 17 nm Ag₂S@TiO₂ sample which is ~70% better than the previously reported for Ag₂S/TiO₂ hierarchical spheres. This was attributed to the efficient charge separation and transfer driven by increased visible-light absorption, bandgap narrowing and reduced electron-hole recombination rates. The present study demonstrate the potential utilization of Ag₂S@TiO₂ nanofibers in filtration membranes for removal of organic pollutants from wastewater.

Gold-silver@TiO2 nanocomposite-modified plasmonic photoanodes for higher efficiency dye-sensitized solar cells

In the present investigation, gold-silver@titania (Au-Ag@TiO₂) plasmonic nanocomposite materials with different Au and Ag compositions were prepared using a simple one-step chemical reduction method and used as photoanodes in high-efficiency dye-sensitized solar cells (DSSCs). The Au-Ag incorporated TiO₂ photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 7.33%, which is ∼230% higher than the unmodified TiO₂ photoanode (2.22%) under full sunlight illumination (100 mW cm^-2, AM 1.5G). This superior solar energy conversion efficiency was mainly due to the synergistic effect between the Au and Ag, and their surface plasmon resonance effect, which improved the optical absorption and interfacial charge transfer by minimizing the charge recombination process. The influence of the Au-Ag composition on the overall energy conversion efficiency was also explored, and the optimized composition with TiO₂ was found to be Au₇₅-Ag₂₅. This was reflected in the femtosecond transient absorption dynamics in which the electron-phonon interaction in the Au nanoparticles was measured to be 6.14 ps in TiO₂/Au₇₅:Ag₂₅, compared to 2.38 ps for free Au and 4.02 ps for TiO₂/Au₁₀₀:Ag₀. The slower dynamics indicates a more efficient electron-hole separation in TiO₂/Au₇₅:Ag₂₅ that is attributed to the formation of a Schottky barrier at the interface between TiO₂ and the noble metal(s) that acts as an electron sink. The significant boost in the solar energy conversion efficiency with the Au-Ag@TiO₂ plasmonic nanocomposite showed its potential as a photoanode for high-efficiency DSSCs.

Plasmonic Solar Cells: From Rational Design to Mechanism Overview

Plasmonic effects have been proposed as a solution to overcome the limited light absorption in thin-film photovoltaic devices, and various types of plasmonic solar cells have been developed. This review provides a comprehensive overview of the state-of-the-art progress on the design and fabrication of plasmonic solar cells and their enhancement mechanism. The working principle is first addressed in terms of the combined effects of plasmon decay, scattering, near-field enhancement, and plasmonic energy transfer, including direct hot electron transfer and resonant energy transfer. Then, we summarize recent developments for various types of plasmonic solar cells based on silicon, dye-sensitized, organic photovoltaic, and other types of solar cells, including quantum dot and perovskite variants. We also address several issues regarding the limitations of plasmonic nanostructures, including their electrical, chemical, and physical stability, charge recombination, narrowband absorption, and high cost. Next, we propose a few potentially useful approaches that can improve the performance of plasmonic cells, such as the inclusion of graphene plasmonics, plasmon-upconversion coupling, and coupling between fluorescence resonance energy transfer and plasmon resonance energy transfer. This review is concluded with remarks on future prospects for plasmonic solar cell use.

Synthesis, characterization and multifunctional properties of plasmonic Ag-TiO2 nanocomposites

We report on the synthesis of multifunctional Ag-TiO2 nanocomposites and their optical, physio-chemical, surface enhanced Raman scattering (SERS) and antibacterial properties. A series of Ag-TiO2 nanocomposites were synthesized by sol-gel technique and characterized by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersed x-ray analysis, photoluminescence, UV-vis, x-ray photoelectron and Raman spectroscopy and Brunauer-Emmett-Teller method. The Ag nanoparticles (NPs) (7-20 nm) were found to be uniformly distributed around and strongly attached to TiO2 NPs. The novel optical responses of the nanocomposites are due to the strong electric field from the localized surface plasmon (LSP) excitation of the Ag NPs and decreased recombination of photo-induced electrons and holes at Ag-TiO2 interface providing potential materials for photocatalysis. The nanocomposites show enhancement in the SERS signals of methyl orange (MO) molecules with increasing Ag content attributed to the long-range electromagnetic enhancement from the excited LSP of the Ag NPs. To further understand the SERS activity, molecular mechanics and molecular dynamics simulations were used to study the geometries and SERS enhancement of MO adsorbed onto Ag-TiO2 respectively. Simulation results indicate that number of ligands (MO) that adsorb onto the Ag NPs as well as binding energy per ligand increases with increasing NP density and molecule-to-surface orientation is mainly flat resulting in strong bond strength between MO and Ag NP surface and enhanced SERS signals. The antimicrobial activity of the Ag-TiO2 nanocomposites was tested against the bacterium Staphylococcus aureus and enhanced antibacterial effect was observed with increasing Ag content explained by contact killing action mechanism. These results foresee promising applications of the plasmonic metal-semiconductor based nano-biocomposites for both chemical and biological samples.

Recent Development of Plasmonic Resonance-Based Photocatalysis and Photovoltaics for Solar Utilization

Increasing utilization of solar energy is an effective strategy to tackle our energy and energy-related environmental issues. Both solar photocatalysis (PC) and solar photovoltaics (PV) have high potential to develop technologies of many practical applications. Substantial research efforts are devoted to enhancing visible light activation of the photoelectrocatalytic reactions by various modifications of nanostructured semiconductors. This review paper emphasizes the recent advancement in material modifications by means of the promising localized surface plasmonic resonance (LSPR) mechanisms. The principles of LSPR and its effects on the photonic efficiency of PV and PC are discussed here. Many research findings reveal the promise of Au and Ag plasmonic nanoparticles (NPs). Continual investigation for increasing the stability of the plasmonic NPs will be fruitful.

Fabrication of pristine Mn2O3and Ag–Mn2O3composite thin films by AACVD for photoelectrochemical water splitting

Pristine Mn₂O₃and Ag–Mn₂O₃nanocomposite thin films deposited by AACVD on FTO showed photocurrent densities of 1.8 and 3 mA cm⁻²respectively.

Surface plasmon-enhanced dye-sensitized solar cells based on double-layered composite films consisting of TiO2/Ag and TiO2/Au nanoparticles

Double-layered composite films consisting of TiO₂/Ag and TiO₂/Au nanoparticles.

Nano polypropylenimine dendrimer (DAB-PPI-G1): as a novel nano basic-polymer catalyst for one-pot synthesis of 2-amino-2-chromene derivatives

For the first time, a novel nano basic-polymer catalyst for the green synthesis of new 2-amino-2-chromene derivatives, avoiding the use of any metal or acid catalysts, is proposed.

Multi-functional DNA-based synthesis of SWNTs@(TiO2/Ag/Au) nanocomposites for enhanced light-harvesting and charge collection in DSSCs

Based on multi-functional DNA templates, SWNTs@(TiO₂/Ag/Au) nanocomposites were synthesized to enhance the light-harvesting and charge collection efficiency of DSSCs.

Reductant-assisted synthesis, characterization and photovoltaic characteristics of ligand-protected gold nanoparticles

Influence of nano-particles sizes on photovoltaic characteristics.

Hybrid silver nanoparticle/nanocluster-decorated polypyrrole for high-performance supercapacitors

Schematic representation of the evolution of different Ag@PPy nanocomposites.

Improved electrochemical and photovoltaic performance of dye sensitized solar cells based on PEO/PVDF–HFP/silane modified TiO2 electrolytes and MWCNT/Nafion® counter electrode

Solid state dye sensitized solar cells based on PEO/PVDF–HFP/M-TiO₂.

Facile synthesis of Au@TiO2 nanocomposite and its application as a photoanode in dye-sensitized solar cells

Au@TiO₂ nanocomposite materials were synthesized by a facile one-step chemical reduction method and employed as photoanodes in dye-sensitized solar cells.

Aligned carbon nanotube/polymer hybrid electrolytes for high performance dye sensitized solar cell applications

Electrically aligned MWCNT/PEO/PVDF-HFP nanocomposite electrolyte membrane based solid state dye sensitized solar cell shows a power conversion efficiency of about 4%.

Photocatalytic activity of Ag nanoparticle-dispersed N-TiO2 nanofilms prepared by magnetron sputtering

N-TiO₂ nanofilms dispersed with Ag nanoparticles on glass substrates were prepared by magnetron sputtering, and their photocatalytic activity for the degradation of methylene blue in aqueous solution was investigated.

Promotional effect of silver nanoparticles on the performance of N-doped TiO2 photoanode-based dye-sensitized solar cells

We report the first successful application of an N-TiO₂–Ag nanocomposite as an efficient photoanode for highly efficient dye-sensitized solar cells (DSSC).