Efficient photocatalysis with graphene oxide/Ag/Ag2S–TiO2 nanocomposites under visible light irradiation

Lack of visible light response and low quantum yield hinder the practical application of TiO₂ as a high-performance photocatalyst. Herein, we present a rational design of TiO₂ nanorod arrays (NRAs) decorated with Ag/Ag₂S nanoparticles (NPs) synthesized through successive ion layer adsorption and reaction (SILAR) and covered by graphene oxide (GO) at room temperature. Ag/Ag₂S NPs with uniform sizes are well-dispersed on the TiO₂ nanorods (NRs) as evidenced by electron microscopic analyses. The photocatalyst GO/Ag/Ag₂S decorated TiO₂ NRAs shows much higher visible light absorption response, which leads to remarkably enhanced photocatalytic activities on both dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 600% higher than that of pure TiO₂ sample under visible light. This remarkable enhancement can be attributed to a synergy of electron-sink function and surface plasmon resonance (SPR) of Ag NPs, band matching of Ag₂S NPs, and rapid charge carrier transport by GO, which significantly improves charge separation of the photoexcited TiO₂. The photocurrent density of GO/Ag/Ag₂S–TiO₂ NRAs reached to maximum (i.e. 6.77 mA cm⁻²vs. 0 V). Our study proves that the rational design of composite nanostructures enhances the photocatalytic activity under visible light, and efficiently utilizes the complete solar spectrum for pollutant degradation.

The photocatalytic reaction efficiency of GO/Ag/Ag₂S–TiO₂ nanorod arrays is 600% higher than that of a pure TiO₂ sample under visible light.     

Natural assembly of a ternary Ag–SnS–TiO2 photocatalyst and its photocatalytic performance under simulated sunlight

Natural assembly method was utilized to prepare a novel ternary Ag–SnS–TiO₂ nanocomposite, in which TiO₂ nanobelts were used as templates. The co-loading of Ag and SnS nanoparticles endows TiO₂ nanobelts with enhanced photocatalytic capability, resulting from the broadened light absorption spectra and decreased band gaps. Comparing with raw TiO₂ nanobelts and commercial Degussa P25, an improvement in photodegradation of simulated organic pollutants was successfully demonstrated due to the decreasing recombination of photogenerated electron–hole pairs. Our work presents a new strategy for the preparation of ternary TiO₂-based photocatalysts in the practical application of wastewater treatment.

Natural assembly method was utilized to prepare a novel ternary Ag–SnS–TiO₂ nanocomposite, in which TiO₂ nanobelts were used as templates.     

A novel multifunctional Ag and Sr2+ co-doped TiO2@rGO ternary nanocomposite with enhanced p-nitrophenol degradation,and bactericidal and hydrogen evolution activity

In the present study, a novel multifunctional Sr²⁺/Ag–TiO₂@rGO ternary hybrid photocatalyst was prepared via facile sol–gel and hydrothermal methods. The prepared catalyst was well characterized by UV-vis, XRD, Raman, HRTEM and XPS. The synthesized composite was utilised for p-NP degradation, E. coli disinfection and H₂ generation under visible light. The Sr²⁺/Ag–TiO₂@rGO catalyst showed enhanced photocatalytic H₂ evolution rate (64.3 μmol h⁻¹) compared with Ag–TiO₂@rGO (30.1 μmol h⁻¹) and TiO₂ (no activity). Nearly complete degradation of 15 mg l⁻¹p-NP was achieved over Sr²⁺/Ag–TiO₂@rGO after 3 h, while only 66% and 5% was achieved by Ag–TiO₂@rGO and TiO₂ respectively. Furthermore, TEM analysis was carried out on Escherichia coli (E. coli) before and after visible light irradiation to understand the inactivation mechanism and DNA analysis indicated no fragmentation during inactivation. Radical quantification experiments and ESR analysis suggested that ·OH and O₂˙⁻ were the main ROS in the degradation and disinfection processes. The superior photocatalytic H₂ evolution rate of Sr²⁺/Ag–TiO₂@rGO was attributed to the synergetic effect between the Ag, Sr²⁺ and TiO₂ components on the rGO surface. The localized SPR effect of Ag induced visible light generated charge carriers into the conduction band of the TiO₂ and Sr²⁺ which further transfer to the rGO for the reduction of H⁺ ions into H₂. The results suggest that Sr²⁺/Ag–TiO₂@rGO structures could not only induce separation and migration efficiency of charge carries, but also improve charge collection efficiency for enhanced catalytic activity. Thus, we believe that this work could provide new insights into multifunctional nanomaterials for applications in solar photocatalytic degradation of harmful organics and pathogenic bacteria with clean energy generation during wastewater treatment.

In the present study, a novel multifunctional Sr²⁺/Ag–TiO₂@rGO ternary hybrid photocatalyst was prepared via facile sol–gel and hydrothermal methods.     

Rational design of a polypyrrole-based competent bifunctional magnetic nanocatalyst

The combination of conducting polymers with semiconductors for the fabrication of organic/inorganic hybrid nanocatalysts is one of the most promising research areas for many applications. In this work, the synthesized nanocomposite combines several advantages such as the photoresponse shift from the UV region toward visible light by narrowing the band gap of the semiconductor, magnetic separation ability and dual applications including the catalytic reduction of p-nitrophenol (PNP) and the photocatalytic degradation of methylene blue (MB) dye. In addition to the core magnetite nanoparticles (NPs), the synthesized nanocomposite contains polypyrrole (PPY) and TiO₂ shells that are decorated with silver metal NPs to prevent electron–hole recombination and to enhance the catalytic performance. Indeed, the catalytic PNP reduction experiments reveal that the synthesized nanocomposite exhibits significantly high catalytic activity with a rate constant of 0.1169 min⁻¹. Moreover, the photocatalytic experiments show that the synthesized nanophotocatalyst has a boosting effect toward MB dye degradation under normal daytime visible light irradiation with a rate constant of 6.38 × 10⁻² min⁻¹. The synergetic effect between silver NPs, PPY and TiO₂ is thought to play a fundamental role in enhancing the photocatalytic activity.

An efficient method to synthesize a magnetic nanocomposite with dual catalytic activities with a synergetic effect between Ag nanoparticles, polypyrrole and TiO₂ is described.     

Enhanced antibacterial properties of biocompatible titanium via electrochemically deposited Ag/TiO2 nanotubes and chitosan–gelatin–Ag–ZnO complex coating

A novel double-layered antibacterial coating was fabricated on pure titanium (Ti) via a simple three-step electrodeposition process. Scanning electronic microscopy (SEM) images show that the coating was constructed with the inner layer of TiO₂ nanotubes doped with silver nanoparticles (TNTs/Ag) and the outer layer of chitosan–gelatin mixture with zinc oxide and silver nanoparticles (CS–Gel–Ag–ZnO). In comparison, we also investigated the composition, structure and antibacterial properties of pure Ti coated with TNTs, TNTs/Ag or TNTs/Ag + CS–Gel–Ag–ZnO, respectively. The TNTs was about 100 nm wide and 240 nm to 370 nm tall, and most Ag nanoparticles (Ag NPs) with diameter smaller than 20 nm were successfully deposited inside the tubes. The CS–Gel–Ag–ZnO layer was continuous and uniform. Antibacterial activity against planktonic and adherent bacteria were both investigated. Agar diffusion test against Staphylococcus aureus (S. aureus) shows improved antibacterial capacity of the TNTs/Ag + CS–Gel–Ag–ZnO coating, with a clear zone of inhibition (ZOI) up to 14.5 mm wide. Dead adherent bacteria were found on the surface by SEM. The antibacterial rate against planktonic S. aureus was as high as 99.2% over the 24 h incubation period.

A novel complex antibacterial coating fabricated via a simple three-step electrodeposition process shows high antibacterial rate of 99.2%.     

Fabrication,characterization and high photocatalytic activity of Ag–ZnO heterojunctions under UV-visible light

Pure ZnO and Ag–ZnO nanocomposites were fabricated via a sol–gel route, and the obtained photocatalysts were characterized by XRD, SEM, TEM, BET, XPS, PL and DRS. The results showed that Ag⁰ nanoparticles deposit on the ZnO surface and Ag modification has negligible impact on the crystal structure, surface hydroxyl group content and surface area of ZnO. However, the recombination of photogenerated electrons and holes was suppressed effectively by Ag loading. The photocatalytic activity was investigated by evaluating the degradation of MB under xenon lamp irradiation as the UV-visible light source, and the results show that the photocatalytic activity of ZnO significantly improved after Ag modification. Ag–ZnO photocatalysts exhibit higher photocatalytic activity than commercial photocatalyst P25. The degradation degree of MB for 1%Ag–ZnO was 97.1% after 15 min. ˙O₂⁻ radicals are the main active species responsible for the photodegradation process, and Ag–ZnO heterojunctions generate more ˙O₂⁻ radicals, which is the primary reason for the improved photocatalytic performance.

Ag–ZnO heterojunction promotes the separation of photogenerated pairs and thus exhibits high catalytic activity under UV-visible light.     

Synthesis of Sn/Ag–Sn nanoparticles via room temperature galvanic reaction and diffusion

Tin (Sn) has a low melting temperature, i.e., 231.9 °C for the bulk, and the capability to form compounds with many metals. The galvanic reaction between Sn nanoparticles (NPs) as the core and silver nitrate at room temperature under argon gas in an organic solvent without any reducing power, was employed for the first time to coat an Ag–Sn intermetallic shell, i.e., Ag₃Sn and/or Ag₄Sn, on Sn NPs. For spherical Sn NPs, the NPs retained a spherical shape after coating. Uniform and Janus structures consisting of a β-Sn core with Ag–Sn shell were observed in the resulting NPs and their population related to the input molar ratios of the metal precursors. The observation of the intermetallic shell is general for both spherical and rod-shape Sn NPs. The formation of the intermetallic shell indicated that two reactions occurred sequentially, first reduction of Ag ions to Ag atoms by the Sn core, followed by interdiffusion of Ag and Sn to form the Ag–Sn intermetallic shell.

Coating of Ag–Sn intermetallic compound on Sn nanoparticles at room temperature.     

Goethite–titania composite: disinfection mechanism under UV and visible light

Goethite–titania (α-FeOOH–TiO₂) composites were prepared by co-precipitation and mechanical milling. The structural, morphological and optical properties of as-synthesized composites were characterized by X-ray powder diffraction, scanning electron microscopy and UV-Vis diffuse reflectance spectroscopy, respectively. α-FeOOH–TiO₂ composites and TiO₂-P25, as reference, were evaluated as photocatalysts for the disinfection of Escherichia coli under UV or visible light in a stirred tank reactor. α-FeOOH–TiO₂ exhibited better photocatalytic activity in the visible region than TiO₂-P25. The mechanical activation increased the absorption in the visible range of TiO₂-P25 and the photocatalytic activity of α-FeOOH–TiO₂. In the experiments with UV light and α-FeOOH–TiO₂, mechanically activated, a 5.4 log-reduction of bacteria was achieved after 240 min of treatment. Using visible light the α-FeOOH–TiO₂ and the TiO₂-P25 showed a 3.1 and a 0.7 log-reductions at 240 min, respectively. The disinfection mechanism was studied by ROS detection and scavenger experiments, demonstrating that the main ROS produced in the disinfection process were superoxide radical anion, singlet oxygen and hydroxyl radical.

A photocatalytic mechanism for FeOOH–TiO₂ composite is proposed under UV-Vis light, the FeOOH–TiO₂ composite showed higher photocatalytic activity than TiO₂-P25.     

Localized surface plasmon resonance enhanced photocatalysis: an experimental and theoretical mechanistic investigation

Titanium dioxide (TiO₂) is an advantageous material in catalytic photodegradation due to its low cost, high stability, and considerably higher efficiency when compared to other semiconductors. However, the need for artificial radiation sources in the UV range is a limitation to its use in wastewater remediation. In this context, Localized Surface Plasmon Resonance (LSPR) has been shown to enhance the photoexcitation of charge carriers in the semiconductor. In the present work, the investigation of catalytic photodegradation of phenol solution under distinct excitation by UV-visible or just visible radiation, employing three TiO₂ based plasmonic catalysts, was conducted. Spherical silver nanoparticles which present LSPR along the TiO₂ bandgap energy and electrically insulated silver nanoparticles were employed. Gold nanoparticles, which present low energy LSPR, were also employed in order to compare the excitation efficiency. Discrete dipole approximation simulations were carried out in order to verify the electric field enhancement and penetration at the semiconductor surface of each plasmonic catalyst. The results presented here may help to shed some light with respect to the contribution of plasmonic photocatalysts and the charge transfer mechanism in catalysts containing plasmonic structures.

A theoretical (DDA simulation) and experimental (phenol degradation) study has shown the LSPR from Ag and Ag@SiO₂ NPs to contribute to better TiO₂ photocatalytic performances. Au NPs has shown very low contribution, due to its low energy LSPR.     

Synthesis of Ni–Ag–ZnO solid solution nanoparticles for photoreduction and antimicrobial applications

ZnO is one of the most promising and efficient semiconductor materials for various light-harvesting applications. Herein, we reported the tuning of optical properties of ZnO nanoparticles (NPs) by co-incorporation of Ni and Ag ions in the ZnO lattice. A sonochemical approach was used to synthesize pure ZnO NPs, Ni–ZnO, Ag–ZnO and Ag/Ni–ZnO with different concentrations of Ni and Ag (0.5%, 2%, 4%, 8%, and 15%) and Ni doped Ag–ZnO solid solutions with 0.25%, 0.5%, and 5% Ni ions. The as-synthesized Ni–Ag–ZnO solid solution NPs were characterized by powdered X-ray diffraction (pXRD), FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), UV-vis (UV) spectroscopy, and photoluminescence (PL) spectroscopy. Ni–Ag co-incorporation into a ZnO lattice reduces charge recombination by inducing charge trap states between the valence and conduction bands of ZnO and interfacial transfer of electrons. The Ni doped Ag–ZnO solid solution NPs have shown superior 4-nitrophenol reduction compared to pure ZnO NPs which do not show this reaction. Furthermore, a methylene blue (MB) clock reaction was also performed. Antibacterial activity against E. coli and S. aureus has inhibited the growth pattern of both strains depending on the concentration of catalysts.

The synergic effect of Ni and Ag in Ni–Ag–ZnO solid solutions has tuned the optoelectronic properties of ZnO for photoreduction reactions.     

Compact TiO2 films with sandwiched Ag nanoparticles as electron-collecting layer in planar type perovskite solar cells: improvement in efficiency and stability

Fabrication of perovskite solar cells (PSCs) in a simple way with high efficiency and stability remains a challenge. In this study, silver nanoparticles (Ag NPs) were sandwiched between two compact TiO₂ layers through a facile process of spin-coating an ethanolic AgNO₃ solution, followed by thermal annealing. The presence of Ag NPs in the electron-transporting layer of TiO₂ improved the light input to the device, the morphology of the perovskite film prepared on top, and eliminated leakage current. Photoluminescence and electron mobility studies revealed that the incorporation of Ag NPs in the ETL of the planar PSC device facilitated the electron–hole separation and promoted charge extraction and transport from perovskite to ETL. Hysteresis-free devices with incorporated Ag NPs gave a high average short-circuit current density (J_sc) of 22.91 ± 0.39 mA cm⁻² and maximum power conversion efficiency of 17.25%. The devices also showed enhanced stability versus a control device without embedded Ag NPs. The possible reasons for the improvement are analyzed and discussed.

Embedding silver nanoparticles in the compact TiO₂ layer effectively improves the efficiency and stability of a perovskite solar cell.     

Modified graphene supported Ag–Cu NPs with enhanced bimetallic synergistic effect in oxidation and Chan–Lam coupling reactions

Herein, well dispersed Ag–Cu NPs supported on modified graphene have been synthesized via a facile and rapid approach using sodium borohydride as a reducing agent under ambient conditions. Dicyandiamide is selected as an effective nitrogen source with TiO₂ as an inorganic material to form two kinds of supports, labelled as TiO₂–NGO and NTiO₂–GO. Initially, the surface area analysis of these two support materials was carried out which indicated that N-doping of GO followed by anchoring with TiO₂ has produced support material of larger surface area. Using both types of supports, ten nano-metal catalysts based on Ag and Cu were synthesized. Benefiting from the bimetallic synergistic effect and larger specific surface area of TiO₂–NGO, Cu@Ag–TiO₂–NGO is found to be a highly active and reusable catalyst out of other synthesized catalysts. It exhibits excellent catalytic activity for oxidation of alcohols and hydrocarbons as well as Chan–Lam coupling reactions. The nanocatalyst is intensively characterized by BET, SEM, HR-TEM, ICP-AES, EDX, CHN, FT-IR, TGA, XRD and XPS.

Cu@Ag–TiO₂–NGO prepared from modified graphene by simple methodology exhibits enhanced catalytic activity towards oxidation and Chan–Lam coupling due to the synergistic effect between Ag and Cu NPs.     

Ag0/Au0 nanocluster loaded Bi2O4 photocatalyst for methyl orange dye photodegradation

Visible-light-sensitive Ag and Au nanocluster loaded Bi₂O₄ (Ag–Bi₂O₄ and Au–Bi₂O₄) semiconductor photocatalysts have been synthesized. The composite materials exhibited increased photocatalytic degradation of the azo-dye pollutant, Methyl Orange (MO). In addition, Au–Bi₂O₄ (Au-7% wt) showed the highest MO degradation rate (0.05904 min⁻¹) i.e. 7.69 times higher than the pristine Bi₂O₄ and 1.4 times higher than 1% Ag–Bi₂O₄. The optical properties of the composites showed that the band gaps of the composite samples 1% Ag–Bi₂O₄ and 7% Au–Bi₂O₄ were 1.96 eV and 2.09 eV, respectively. The increase in the degradation rate is attributed to the decrease of the recombination rate of photoinduced e⁻/h⁺, caused by the enhanced charge transfer between the metal nanoparticles and Bi₂O₄ as confirmed in the photocurrent measurements. The photocurrent measurements showed increase in the transients output by 8.25 times and 2.75 times for 1% Ag–Bi₂O₄ & 3% Au–Bi₂O₄, respectively as compared to that of the pristine Bi₂O₄. These features further aided the increase in the photocatalytic efficiency while retaining the original physical properties, thus showing the robustness of Bi₂O₄ as a photocatalyst.

Illustration of charge transfer between Bi₂O₄ and nanoclusters, and photocatalytic MO degradation by M/Bi₂O₄ under visible light irradiation (M = Ag or Au).     

New insights into the surface plasmon resonance (SPR) driven photocatalytic H2 production of Au–TiO2

The Surface Plasmon Resonance (SPR) driven photocatalytic H₂ production upon visible light illumination (≥500 nm) was investigated on gold-loaded TiO₂ (Au–TiO₂). It has been clearly shown that the Au-SPR can directly lead to photocatalytic H₂ evolution under illumination (≥500 nm). However, there are still some open issues about the underlying mechanism for the SPR-driven photocatalytic H₂ production, especially the explanation of the resonance energy transfer (RET) theory and the direct electron transfer (DET) theory. In this contribution, by means of the EPR and laser flash photolysis spectroscopy, we clearly showed the signals for different species formed by trapped electrons and holes in TiO₂ upon visible light illumination (≥500 nm). However, the energy of the Au-SPR is insufficient to overcome the bandgap of TiO₂. The signals of the trapped electrons and holes originate from two distinct processes, rather than the simple electron–hole pair excitation. Results obtained by Laser Flash Photolysis spectroscopy evidenced that, due to the Au-SPR effect, Au NPs can inject electrons to the conduction band of TiO₂ and the Au-SPR can also initiate e⁻/h⁺ pair generation (interfacial charge transfer process) upon visible light illumination (≥500 nm). Moreover, the Density Functional Theory (DFT) calculation provided direct evidence that, due to the Au-SPR, new impurity energy levels occurred, thus further theoretically elaborating the proposed mechanisms.

The Surface Plasmon Resonance (SPR) driven photocatalytic H₂ production upon visible light illumination (≥500 nm) was investigated on gold-loaded TiO₂ (Au–TiO₂).     

Highly efficient core–shell Ag@carbon dot modified TiO2 nanofibers for photocatalytic degradation of organic pollutants and their SERS monitoring

In the present study, a novel hybrid nanomaterial composed of core–shell structured Ag@carbon dot (CD) modified TiO₂ nanofibers (NFs) was successfully fabricated via a simple two-step strategy for the first time. Herein, the Ag@CDs–TiO₂ NFs are demonstrated to be an efficient SERS substrate. The strong LSPR-induced electromagnetic enhancement (EM) by Ag@CDs NPs and efficient charge transfer (CT) effect between Ag@CDs and TiO₂ NFs synergistically contribute to the excellent SERS enhancement. In addition, the Ag@CDs–TiO₂ NFs exhibit enhanced photocatalytic activity regarding the organic pollutant degradation under visible light irradiation because of the enhanced light absorption and improved separation of photo-generated electron–hole pairs. Thus, this new nanocomposite can be used as a sensitive SERS substrate for determining the catalytic activity and reaction kinetics during the photodegradation of methylene blue (MB). Compared with UV-vis spectroscopy, the SERS technique enables more accurate monitoring of the changes of adsorption molecules and actual catalytic process on the surface of the catalyst. These results are significant for the development of metal or semiconductor-based catalysts for ensuring optoelectronic, energy and environmental applications.

The possible mechanism of enhanced photocatalytic performance of Ag@CDs–TiO₂ hybrid NFs.     

Synergistic effect of Ni–Ag–rutile TiO2 ternary nanocomposite for efficient visible-light-driven photocatalytic activity

P25 comprising of mixed anatase and rutile phases is known to be highly photocatalytically active compared to the individual phases. Using a facile wet chemical method, we demonstrate a ternary nanocomposite consisting of Ni and Ag nanoparticles, decorated on the surface of XTiO₂ (X: P25, rutile (R)) as an efficient visible-light-driven photocatalyst. Contrary to the current perspective, RTiO₂-based Ni–Ag–RTiO₂ shows the highest activity with the H₂ evolution rate of ∼86 μmol g⁻¹ W⁻¹ h⁻¹@535 nm. Together with quantitative assessment of active Ni, Ag and XTiO₂ in these ternary systems using high energy synchrotron X-ray diffraction, transmission electron microscopy coupled energy dispersive spectroscopy mapping evidences the metal to semiconductor contact via Ag. The robust photocatalytic activity is attributed to the improved visible light absorption, as noted by the observed band edge of ∼2.67 eV corroborating well with the occurrence of Ti³⁺ in Ti 2p XPS. The effective charge separation due to intimate contact between Ni and RTiO₂via Ag is further evidenced by the plasmon loss peak in Ag 3d XPS. Moreover, density functional theory calculations revealed enhanced adsorption of H₂ on Ti₈O₁₆ clusters when both Ag and Ni are simultaneously present, owing to the hybridization of the metal atoms with d orbitals of Ti and p orbitals of O leading to enhanced bonding characteristics, as substantiated by the density of states. Additionally, the variation in the electronegativity in Bader charge analysis indicates the possibility of hydrogen evolution at the Ni sites, in agreement with the experimental observations.

Robust photocatalytic activity of Ni–Ag–RTiO₂ is attributed to the improved visible light absorption and effective charge separation due to intimate contact between Ni and RTiO₂via Ag, as evidenced by Ti³⁺ in Ti 2p XPS and energy dispersive mapping.     

Mesoporous Cu–Cu2O@TiO2 heterojunction photocatalysts derived from metal–organic frameworks

This study reveals a unique Cu–Cu₂O@TiO₂ heterojunction photocatalyst obtained with metal–organic framework as the precursor, which can be utilized in dye photodegradation under visible light irradiation. The composition, structure, morphology, porosity, optical properties and photocatalytic performance of the obtained catalysts were all investigated in detail. The Cu–Cu₂O@TiO₂ nanocomposite is composed of lamellar Cu–Cu₂O microspheres embedded by numerous TiO₂ nanoparticles. Methylene blue, methyl orange and 4-nitrophenol were used as model pollutants to evaluate the photocatalytic activity of the Cu–Cu₂O@TiO₂ nanocomposite for dye degradation under visible light irradiation. Nearly 95% decolourisation efficiency of Methylene blue was achieved by the Cu–Cu₂O@TiO₂ photocatalyst within 3 h, which is much higher than that of TiO₂ or Cu₂O catalysts. The excellent photocatalytic activity was primarily attributed to the unique MOF-based mesoporous structure, the enlarged photo-adsorption range and the efficient separation of the charge carriers in the Cu–Cu₂O@TiO₂ heterojunction.

Cu–Cu₂O@TiO₂ heterojunction photocatalyst derived from a metal–organic framework shows high photocatalytic activity for dye degradation under visible light irradiation.     

Biosynthesis of Ag–Pd bimetallic alloy nanoparticles through hydrolysis of cellulose triggered by silver sulfate

We report a simple but efficient biological route based on the hydrolysis of cellulose to synthesize Ag–Pd alloy nanoparticles (NPs) under hydrothermal conditions. X-ray powder diffraction, ultraviolet-visible spectroscopy and scanning transmission electron microscopy-energy dispersive X-ray analyses were used to study and demonstrate the alloy nature. The microscopy results showed that well-defined Ag–Pd alloy NPs of about 59.7 nm in size can be biosynthesized at 200 °C for 10 h. Fourier transform infrared spectroscopy indicated that, triggered by silver sulfate, cellulose was hydrolyzed into saccharides or aldehydes, which served as both reductants and stabilizers, and accounted for the formation of the well-defined Ag–Pd NPs. Moreover, the as-synthesized Ag–Pd nanoalloy showed high activity in the catalytic reduction of 4-nitrophenol by NaBH₄.

We report a simple but efficient biological route based on the hydrolysis of cellulose to synthesize Ag–Pd alloy nanoparticles (NPs) under hydrothermal conditions.     

Explosives sensing using Ag–Cu alloy nanoparticles synthesized by femtosecond laser ablation and irradiation

Herein we demonstrate the synthesis of Ag–Cu alloy NPs through a consecutive two-step process; laser ablation followed by laser irradiation. Initially, pure Ag and Cu NPs were produced individually using the laser ablation in liquid technique (with ∼50 femtosecond pulses at 800 nm) which was followed by laser irradiation of the mixed Ag and Cu NPs in equal volume. These Ag, Cu, and Ag–Cu NPs were characterised by UV-visible absorption, HRTEM and XRD techniques. The alloy formation was confirmed by the presence of a single surface plasmon resonance peak in absorption spectra and elemental mapping using FESEM techniques. Furthermore, the results from surface enhanced Raman scattering (SERS) studies performed for the methylene blue (MB) molecule suggested that Ag–Cu alloy NPs demonstrate a higher enhancement factor (EF) compared to pure Ag/Cu NPs. Additionally, SERS studies of Ag–Cu alloy NPs were implemented for the detection of explosive molecules such as picric acid (PA – 5 μM), ammonium nitrate (AN – 5 μM) and the dye molecule methylene blue (MB – 5 nM). These alloy NPs exhibited superiority in the detection of various analyte molecules with good reproducibility and high sensitivity with EFs in the range of 10⁴ to 10⁷.

Herein we demonstrate the synthesis of Ag–Cu alloy NPs through a consecutive two-step process; laser ablation followed by laser irradiation.     

Vitamin C assisted synthesis of rGO–Ag/PANI nanocomposites for improved photocatalytic degradation of pharmaceutical wastes

A highly efficient visible light active polyaniline (PANI)/Ag composites grafted reduced graphene oxide (rGO–Ag/PANI) was prepared for the efficient photocatalytic degradation of paracetamol. The structural, morphological, and light absorption properties of the as-synthesized rGO–Ag/PANI were characterized by UV-Visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Paracetamol was taken as a model water pollutant to investigate the photocatalytic degradation efficiency of the rGO–PANI/Ag nanocomposites under visible light radiation. The result shows the degradation of paracetamol to be 99.6% in the acidic medium (pH 5) and 75.76% in the basic medium (pH 9), respectively. The enhanced degradation efficiency is attributed to the synergetic effect of rGO, PANI, and Ag NPs in the nanocomposites. This synergy of the rGO–Ag/PANI is explained by the strong adsorption efficiency, charge separation, and light absorption in the visible region.

A highly efficient visible light active polyaniline (PANI)/Ag composites grafted reduced graphene oxide (rGO–Ag/PANI) was prepared for the efficient photocatalytic degradation of paracetamol.