Microstructure–mechanical properties of Ag0/Au0 doped K–Mg–Al–Si–O–F glass-ceramics

In understanding the catalytic efficacy of silver (Ag⁰) and gold (Au⁰) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure–machinability correlation of a SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ system is studied. The thermal parameters viz., glass transition temperature (T_g) and crystallization temperature (T_c) were extensively changed by varying NPs (in situ or ex situ). Tc was found to be increased (T_c = 870–875 °C) by 90–110 °C when ex situ NPs were present in the glass system. Under controlled heat-treatment at 950 ± 10 °C, the glasses were converted into glass-ceramics with the predominant presence of crystalline phase (XRD) fluorophlogopite mica, [KMg₃(AlSi₃O₁₀)F₂]. Along with the secondary phase enstatite (MgSiO₃), the presence of Ag and Au particles (FCC system) were identified by XRD. A microstructure containing spherical crystallite precipitates (∼50–400 nm) has been observed through FESEM in in situ doped GCs. An ex situ Ag doped GC matrix composed of rock-like and plate-like crystallites mostly of size 1–3 μm ensured its superior machinability. Vicker''s and Knoop microhardness of in situ doped GCs were estimated within the range 4.45–4.61 GPa which is reduced to 4.21–4.34 GPa in the ex situ Ag system. Machinability of GCs was found to be in the order, ex situ Ag > ex situ Au ∼ in situ Ag > in situ Au. Thus, the ex situ Ag/Au doped SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ GC has potential for use as a machinable glass-ceramic.

In understanding the catalytic efficacy of silver (Ag⁰) and gold (Au⁰) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure–machinability correlation of a SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ system is studied.     

Photocatalytic activity of Ag/Al2O3–Gd2O3 photocatalysts prepared by the sol–gel method in the degradation of 4-chlorophenol

The photocatalytic activity in the degradation of 4-chlorophenol (4-ClPh) in aqueous medium (80 ppm) using 2.0 wt% Ag/Al₂O₃–Gd₂O₃ (Ag/Al–Gd-x; where x = 2.0, 5.0, 15.0, 25.0 and 50.0 wt% of Gd₂O₃) photocatalysts prepared by the sol–gel method was studied under UV light irradiation. The photocatalysts were characterized by N₂ physisorption, X-ray diffraction, SEM, HRTEM, UV-Vis, XPS, FTIR and fluorescence spectroscopy. About 67.0% of 4-ClPh was photoconverted after 4 h of UV light irradiation using Ag/γ-–Al₂O₃. When Ag/Al–Gd-x photocatalysts were tested, the 4-ClPh photoconversion was improved and more than 90.0% of 4-ClPh was photoconverted after 3 h of UV light irradiation in the materials containing 15.0 and 25.0 wt% of Gd₂O₃. Ag/Al–Gd-25 was the material with the highest efficacy to mineralize dissolved organic carbon, mineralizing more than 85.0% after 4 h of UV light irradiation. Silver nanoparticles and micro-particles of irregular pentagonal shape intersected by plane nanobelts of Al₂O₃–Gd₂O₃ composite oxide were detected in the Ag/Al–Gd-25 photocatalyst. This material is characterized by a lowest recombination rate of electron–hole pairs. The low recombination rate of photo-induced electron–hole pairs in the Ag/Al–Gd-x photocatalysts with high Gd₂O₃ contents (≥15.0 wt%) confirmes that the presence of silver nanoparticles and microparticles interacting with Al₂O₃–Gd₂O₃ composite oxide entities favors the separation of photo-induced charges (e⁻ and h⁺). These materials could be appropriate to be used as highly efficient photocatalysts to eliminate high concentrations of 4-ClPh in aqueous medium.

Ag/Al₂O₃–Gd₂O₃ showed high efficacy to photodegradate 4-chlorophenol, the strong interaction between silver nano-particles and micro-particles and Al₂O₃–Gd₂O₃ entities favors the decrease in the recombination rate.     

Counterion coupled (COCO) gemini surfactant capped Ag/Au alloy and Ag@Au core–shell nanoparticles for cancer therapy

Hybrid silver (Ag)–gold (Au) nanoparticles (NPs) with different sizes and compositions were synthesized. Ag/Au alloy and Ag@Au core–shell type NPs were prepared from Ag and Au with various ratios using the COCO gemini surfactant, 1,6-bis (N,N-hexadecyldimethylammonium) adipate (COCOGS), 16-6-16 as a stabilizer. The formation of the Ag/Au alloy and Ag@Au core–shell was confirmed by UV-visible absorption spectroscopy, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX) and selected area electron diffraction (SAED) patterns. Depending on the composition of the Ag/Au alloy NPs, the λ_max values varied from 408 nm to 525 nm. FTIR measurements were used to evaluate the adsorption of the COCO gemini surfactant (16-6-16) on the Ag/Au alloy and Ag@Au core–shell surface. In this present work, we study how to achieve the stability and activity of the COCO gemini surfactant (16-6-16) capped Ag/Au alloy and Ag@Au core–shell NPs for developing novel anti-cancer agents by evaluating their potentials in the Hep-2 cell line model. Thus the developed core–shell NPs were possibly involved in inducing cytotoxicity followed by inhibition of cell proliferation to the cancer cells with apoptosis induction. The developed core–shell NPs might serve as highly applicable agents in the development of next-generation cancer chemotherapeutic agents.

In this work hybrid silver (Ag)–gold (Au) nanoparticles (NPs) with different sizes and compositions were synthesized and applied for anticancer evaluations and which is effectively involved in cancer cell apoptosis through DNA damage.     

Au–Ag and Pt–Ag bimetallic nanoparticles@halloysite nanotubes: morphological modulation,improvement of thermal stability and catalytic performance

In this study, Au–Ag and Pt–Ag bimetallic nanocages were loaded on natural halloysite nanotubes (HNTs) via galvanic exchange based on Ag@HNT. By changing the ratio of Au to Ag or Pt to Ag in exchange processes, Au–Ag@HNT and Pt–Ag@HNT with different nanostructures were generated. Both Au–Ag@HNT and Pt–Ag@HNT systems showed significantly improved efficiency as peroxidase-like catalysts in the oxidation of o-phenylenediamine compared with monometallic Au@HNT and Pt@HNT, although inert Ag is dominant in the composition of both Au–Ag and Pt–Ag nanocages. On the other hand, loading on HNTs enhanced the thermal stability for every system, whether monometallic Ag nanoparticles, bimetallic Au–Ag or Pt–Ag nanocages. Ag@HNT sustained thermal treatment at 400 °C in nitrogen with improved catalytic performance, while Au–Ag@HNT and Pt–Ag@HNT maintained or even had slightly enhanced catalytic efficiency after thermal treatment at 200 °C in nitrogen. This study demonstrated that natural halloysite nanotubes are a good support for various metallic nanoparticles, improving their catalytic efficiency and thermal stability.

Bimetallic Au–Ag@HNT and Pt–Ag@HNT nanocages showed significantly improved efficiency in the oxidation of o-phenylenediamine as peroxidase-like catalyst compared with corresponding monometallic nanoparticles.     

Formation mechanism of MnxCo3−xO4 yolk–shell structures

Formation of Mn_xCo_3−xO₄ yolk–shell microspheres via a solvothermal reaction of hydrated cobalt and manganese nitrates in ethanol is investigated. Spinel nanocrystals of cobalt oxide or cobalt-rich ternary oxide preferentially develop in the system, while manganese-rich hydroxide form Mn(OH)₂-type nanosheets. Instead of continuing to grow individually, the nanocrystallites and nanosheets aggregate into large microspheres due to their strong inter-particle interaction. When the proportion of Mn-rich nanosheets is high, therefore the overall density is low, dehydration of hydroxide nanosheets and a surface re-crystallisation lead to formation of a dense and rigid shell, which is separated from a solid or hollow core via a further Ostwald ripening process. The proposed formation mechanism of the yolk–shell structures based on electron microscopic studies would help us to develop yolk–shell structure based multifunctional materials.

A formation mechanism of yolk–shell microspheres of Mn-rich spinel Mn_xCo_3−xO₄ is proposed based on the analyses of microstructures and local compositions.     

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%.     

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.     

Co3O4–Ag photocatalysts for the efficient degradation of methyl orange

In this paper, a series of Co₃O₄–Ag photocatalysts with different Ag loadings were synthesized by facile hydrothermal and in situ photoreduction methods and fully characterized by XRD, SEM, TEM, FTIR spectroscopy, XPS, UV-vis and PL techniques. The catalysts were used for the degradation of methyl orange (MO). Compared with the pure Co₃O₄ catalyst, the Co₃O₄–Ag catalysts showed better activity; among these, the Co₃O₄–Ag-0.3 catalyst demonstrated the most efficient activity with 96.4% degradation efficiency after 30 h UV light irradiation and high degradation efficiency of 99.1% after 6 h visible light irradiation. According to the corresponding dynamics study under UV light irradiation, the photocatalytic efficiency of Co₃O₄–Ag-0.3 was 2.72 times higher than that of Co₃O₄ under identical reaction conditions. The excellent photocatalytic activity of Co₃O₄–Ag can be attributed to the synergistic effect of strong absorption under UV and visible light, reduced photoelectron and hole recombination rate, and decreased band gap due to Ag doping. Additionally, a possible reaction mechanism over the Co₃O₄–Ag photocatalysts was proposed and explained.

A novel Co₃O₄–Ag catalyst covered on the Ni foam substrate was synthesized via facile hydrothermal and in situ photoreduction methods for the efficient degradation of methyl orange.     

Innovative approach to controlled Pt–Rh bimetallic nanoparticle synthesis

Precise control of the elemental composition and distribution in bimetallic nanoparticles is of great interest for both fundamental studies and applications, e.g. in catalysis. We present a new innovative and facile synthesis strategy for the production of true solid solution Pt_1−xRh_x nanoparticles. This constitutes a development of the established heat-up method, where undesired shell formation is fully suppressed, despite utilizing metal precursors with different reaction rates. The concept is demonstrated through synthesis of selected Pt_1−xRh_x solid solution compositions via the polyalcohol reduction approach. In addition, we provide modified procedures, using the same surface stabilizing agent/metal precursors reaction matrix yielding controlled model Rh(core)–Pt(shell) and Pt(core)–Rh(shell) nanoparticles. Tunable bimetallic solid solution and core–shell nanoparticles with the same capping agent are of key importance in systematic fundamental studies, as functional materials properties may be altered by modifying the surface termination.

In this work, we establish an innovative protocol for the production of Pt–Rh solid solution/core–shell nanoparticles with excellent control of element distribution and composition, built upon the well-established heat-up method.     

Facile solvothermal preparation of Fe3O4–Ag nanocomposite with excellent catalytic performance

Functional nanocomposites demonstrate excellent comprehensive properties and outstanding characteristics for numerous applications. Magnetic nanocomposites are an important type of composite materials, due to their applications in optics, medicine and catalysis. In this report, a new Fe₃O₄-loaded silver (Fe₃O₄–Ag) nanocomposite has been successfully synthesized via a simple solvothermal method and in situ growth of silver nanowires. The silver nanowires were prepared via the reduction of silver vanadate with the addition of uniformly dispersed Fe₃O₄ nanoparticles. Structural and morphological characterizations of the obtained Fe₃O₄–Ag nanocomposite were carried out using many characterization methods. As a new composite catalyst, the synthesized magnetic Fe₃O₄–Ag nanocomposite displayed a high utilization rate of catalytically active sites in catalytic reaction medium and showed good separation and recovery using an external magnetic field. The facile preparation and good catalytic performance of this Fe₃O₄–Ag nanocomposite material demonstrate its potential applications in catalytic treatment and composite materials.

A new Fe₃O₄–Ag nanocomposite was prepared via solvothermal method, demonstrating potential application in catalytic degradation of wastewater treatment and composite materials.     

Environmentally sustainable route to SiO2@Au–Ag nanocomposites for biomedical and catalytic applications

A facile, sustainable, operationally simple and mild method for the synthesis of SiO₂@Au–Ag nanocomposites (NCs) using Nephrolepis cordifolia tuber extract is described and its catalytic, antibacterial and cytotoxic properties were investigated. The fabricated SiO₂@Au–Ag NCs were well characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to determine the optical activity, size and morphology, elemental composition, functional groups present, crystallinity, thermal stability and chemical state respectively. The obtained SiO₂@Au–Ag NCs exhibited spherical shape SiO₂ decorated with Au and Ag nanoparticles. The diameter of the SiO₂ nanoparticles ranges from 200–246 with average 3 nm diameter of Au and Ag NPs. Synthetic utility of this protocol has been demonstrated by exploring its effective catalytic activities for the solvent-free amidation of carboxylic acid with a primary amine with excellent yields. Moreover, the synthesized nanocomposite exhibited as noticeable antibacterial effect against Gram negative and Gram positive bacteria and better bio-compatibility against human keratinocytes. Thus, additive free SiO₂@Au–Ag NCs display the potential for catalysis and biomedical applications.

A facile, sustainable, operationally simple and mild method for the synthesis of SiO₂@Au–Ag nanocomposites (NCs) using Nephrolepis cordifolia tuber extract is described and its catalytic, antibacterial and cytotoxic properties were investigated.     

Facile preparation of porous sheet–sheet hierarchical nanostructure NiO/Ni–Co–Mn–Ox with enhanced specific capacity and cycling stability for high performance supercapacitors

NiO, Ni–Co–Mn–O_x and NiO/Ni–Co–Mn–O_x on nickel foam substrates were prepared via a chemical bath deposition–calcination. The thermodynamic behavior was observed by TG/DTA. The chemical structure and composition, phase structure and microstructures were tested by XPS, XRD, FE-SEM and TEM. The electrochemical performance was measured by CV, GCD and EIS. The mechanism for formation and enhancing electrochemical performance is also discussed. Firstly, the precursors such as NiOOH, CoOOH and MnOOH grow on nickel foam substrates from a homogeneous mixed solution via chemical bath deposition. Thereafter, these precursors are calcined and decomposed into NiO, Co₃O₄ and MnO₂ respectively under different temperatures in a muffle furnace. Notably, NiO/Ni–Co–Mn–O_x on nickel foam substrates reveals a high specific capacity with 1023.50 C g⁻¹ at 1 A g⁻¹ and an excellent capacitance retention with 103.94% at 5 A g⁻¹ after 3000 cycles in 2 M KOH, its outstanding electrochemical performance and cycling stability are mainly attributed to a porous sheet–sheet hierarchical nanostructure and synergistic effects of pseudo-capacitive materials and excellent redox reversibility. Therefore, this research offers a facile synthesis route to transition metal oxides for high performance supercapacitors.

NiO, Ni–Co–Mn–O_x and NiO/Ni–Co–Mn–O_x on nickel foam substrates were prepared via a chemical bath deposition–calcination.     

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.     

Unravelling the one-pot conversion of biomass-derived furfural and levulinic acid to 1,4-pentanediol catalysed by supported RANEY® Ni–Sn alloy catalysts

Bimetallic Ni–Sn alloys have been recognised as promising catalysts for the transformation of furanic compounds and their derivatives into valuable chemicals. Herein, we report the utilisation of a supported bimetallic RANEY® nickel–tin alloy supported on aluminium hydroxide (RNi–Sn(x)/AlOH; x is Ni/Sn molar ratio) catalysts for the one-pot conversion of biomass-derived furfural and levulinic acid to 1,4-pentanediol (1,4-PeD). The as prepared RNi–Sn(1.4)/AlOH catalyst exhibited the highest yield of 1,4-PeD (78%). The reduction of RNi–Sn(x)/AlOH with H₂ at 673–873 K for 1.5 h resulted in the formation of Ni–Sn alloy phases (e.g., Ni₃Sn and Ni₃Sn₂) and caused the transformation of aluminium hydroxide (AlOH) to amorphous alumina (AA). The RNi–Sn(1.4)/AA 673 K/H₂ catalyst contained a Ni₃Sn₂ alloy as the major phase, which exhibited the best yield of 1,4-PeD from furfural (87%) at 433 K, H₂ 3.0 MPa for 12 h and from levulinic acid (up to 90%) at 503 K, H₂ 4.0 MPa, for 12 h. Supported RANEY® Ni–Sn(1.5)/AC and three types of supported Ni–Sn(1.5) alloy (e.g., Ni–Sn(1.5)/AC, Ni–Sn(1.5)/c-AlOH, and Ni–Sn(1.5)/γ-Al₂O₃) catalysts afforded high yields of 1,4-PeD (65–87%) both from furfural and levulinic acid under the optimised reaction conditions.

The RANEY® Ni–Sn(x) alloy catalysed the one-pot conversion of biomass-derived furfural and levulinic acid to allow remarkable yield of 1,4-pentanediol (up to 90%) under the mild reaction conditions.     

Improving the dynamics of a Nd–Mg–Ni-based alloy by combining Ni element and mechanical milling

To improve the reversible kinetics and electrochemical performance of a Nd–Mg–Ni-based alloy, NdMg₁₁Ni + x wt% Ni (x = 100 or 200) samples were prepared through combining the addition of Ni element and ball-milling technology. Meanwhile, the effects of the addition of Ni element and the duration of milling on the NdMg₁₁Ni samples were researched. The results indicate that the addition of Ni element has a beneficial effect on the dynamics of the samples. Meanwhile, the milling duration also has a beneficial effect on the high-rate discharging capabilities, the gaseous hydrogenation rate, and the dehydrogenation dynamics. When the ball-milling time is increased from 5 h to 60 h, the value of R^d₂₀ (the ratio of the dehydrogenation capabilities within 20 min to the saturated hydrogenation capabilities) is raised from 62.20% to 71.59% for the x = 200 sample, and from 58.03% to 64.81% for the x = 100 sample; this is believed to be due to a decline in the activation energy resulting from an increase in the Ni content and ball-milling time. In addition, the E_a value of NdMg₁₁Ni + 200 wt% Ni with a ball-milling time of 60 h is 55.7 kJ mol⁻¹.

Both ball grinding and increasing the nickel content can effectively reduce the dehydrogenation activation energy of a RE–Mg-based alloy.     

Structure analysis of precursor alloy and diffusion during dealloying of Ag–Al alloy

Nanoporous silver (NPS) was fabricated by dealloying Ag–Al alloy ribbons with nominal compositions of 30, 35 and 40 at% Ag (corresponding to hypoeutectic composition, eutectic composition and hypereutectic composition, respectively). The microstructures of the Ag–Al precursor and as-dealloyed samples were observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM) as well as via focused ion beam (FIB) technique. We concluded that with the increase in Ag content from 30 to 40 at%, the diameter of ligament increased from 70 ± 15 nm to 115 ± 35 nm. Due to the method of crystalline solidification and the distribution of α-Al(Ag) and γ-Ag₂Al phases, the as-dealloyed Ag₃₅Al₆₅ alloy exhibited a homogeneous ligament/pore structure, whereas the microstructures of Ag₃₀Al₇₀ and Ag₄₀Al₆₀ showed thinner and coarser ligament structures, respectively.

Nanoporous silver (NPS) was fabricated by dealloying Ag–Al alloy ribbons with nominal compositions of 30, 35 and 40 at% Ag (corresponding to hypoeutectic composition, eutectic composition and hypereutectic composition, respectively).     

The structural transition of bimetallic Ag–Au from core/shell to alloy and SERS application

It is well-known that Ag–Au bimetallic nanoplates have attracted significant research interest due to their unique plasmonic properties and surface-enhanced Raman scattering (SERS). In recent years, there have been many studies on the fabrication of bimetallic nanostructures. However, controlling the shape, size, and structure of bimetallic nanostructures still has many challenges. In this work, we present the results of the synthesis of silver nanoplates (Ag NPls), and Ag–Au bimetallic core/shell and alloy nanostructures, using seed-mediated growth under green LED excitation and a gold salt (HAuCl₄) as a precursor of gold. The results show that the optical properties and crystal structure strongly depend on the amount of added gold salt. Interestingly, when the amount of gold(x) in the sample was less than 0.6 μmol (x < 0.6 μmol), the structural nature of Ag–Au was core/shell, in contrast x > 0.6 μmol gave the alloy structure. The morphology of the obtained nanostructures was investigated using the field emission scanning electron microscopy (FESEM) technique. The UV–Vis extinction spectra of Ag–Au nanostructures showed localized surface plasmon resonance (LSPR) bands in the spectral range of 402–627 nm which changed from two peaks to one peak as the amount of gold increased. Ag–Au core/shell and alloy nanostructures were utilized as surface enhanced Raman scattering (SERS) substrates to detect methylene blue (MB) (10⁻⁷ M concentration). Our experimental observations indicated that the highest enhancement factor (EF) of about 1.2 × 10⁷ was obtained with Ag–Au alloy. Our detailed investigations revealed that the Ag–Au alloy exhibited significant EF compared to pure metal Ag and Ag–Au core/shell nanostructures. Moreover, the analysis of the data revealed a linear dependence between the logarithm of concentration (log C) and the logarithm of SERS signal intensity (log I) in the range of 10⁻⁷–10⁻⁴ M with a correlation coefficient (R²) of 0.994. This research helps us understand better the SERS mechanism and the application of Raman spectroscopy on a bimetallic surface.

It is well-known that Ag–Au bimetallic nanoplates have attracted significant research interest due to their unique plasmonic properties and surface-enhanced Raman scattering (SERS).     

High N2 selectivity in selective catalytic reduction of NO with NH3 over Mn/Ti–Zr catalysts

A series of Mn-based catalysts were prepared by a wet impregnation method for the selective catalytic reduction (SCR) of NO with NH₃. The Mn/Ti–Zr catalyst had more surface area, Lewis acid sites, and Mn⁴⁺ on its surface, and showed excellent activity and high N₂ selectivity in a wide temperature range. NH₃ and NO oxidation was investigated to gain insight into NO reduction and N₂O formation. The formation of N₂O was primarily dominated by the reaction of NO with NH₃ in the presence of O₂via the Eley–Rideal mechanism. An intimate synergistic effect existed between the Mn-based and the Ti–Zr support. It was demonstrated that the Ti–Zr support greatly promoted the catalytic performance of Mn-based catalysts.

The Ti–Zr support greatly promotes the catalytic performance of Mn-based catalysts.     

Improvement of low-temperature NH3-SCR catalytic performance over nitrogen-doped MOx–Cr2O3–La2O3/TiO2–N (M = Cu,Fe, Ce) catalysts

A series of MO_x–Cr₂O₃–La₂O₃/TiO₂–N (M = Cu, Fe, Ce) catalysts with nitrogen doping were prepared via the impregnation method. Comparing the low-temperature NH₃-SCR activity of the catalysts, CeCrLa/Ti–N (xCeO₂–yCr₂O₃–zLa₂O₃/TiO₂–N) exhibited the best catalytic performance (NO conversion approaching 100% at 220–460 °C). The physico-chemical properties of the catalysts were characterized by XRD, BET, SEM, XPS, H₂-TPR, NH₃-TPD and in situ DRIFTS. From the XRD and SEM results, N doping affects the crystalline growth of anatase TiO₂ and MO_x (M = Cu, Fe, Ce, Cr, La) which were well dispersed over the support. Moreover, the doping of N promotes the increase of the Cr⁶⁺/Cr ratio and Ce³⁺/Ce ratio, and the surface chemical adsorption oxygen content, which suggested the improvement of the redox properties of the catalyst. And the surface acid content of the catalyst increased with the doping of N, which is related to CeCrLa/TiO₂–N having the best catalytic activity at high temperature. Therefore, the CeCrLa/TiO₂–N catalyst exhibited the best NH₃-SCR performance and the redox performance of the catalysts is the main factor affecting their activity. Furthermore, in situ DRIFTS analysis indicates that Lewis-acid sites are the main adsorption sites for ammonia onto CeCrLa/TiO₂–N and the catalyst mainly follows the L–H mechanism.

A series of MO_x–Cr₂O₃–La₂O₃/TiO₂–N (M = Cu, Fe, Ce) catalysts with nitrogen doping were prepared via the impregnation method.     

Pt–Nix alloy nanoparticles: a new strategy for cocatalyst design on a CdS surface for photo-catalytic hydrogen generation

Solar photocatalytic water splitting for the production of hydrogen has been a core aspect for decades. A highly active and durable photocatalyst is crucial for the success of the renewable hydrogen economy. To date, the development of highly effective photocatalysts has been seen by the contemporary research community as a grand challenge. Thus, herein we put forward a sincere attempt to use a Pt–Ni_x alloy nanoparticle (NP) cocatalyst loaded CdS photocatalyst ((Pt–Ni_x)/CdS) for photocatalytic hydrogen production under visible light. The Pt–Ni_x alloy NP cocatalyst was synthesized using a one-pot solvothermal method. The cocatalyst nanoparticles were deposited onto the surface of CdS, forming a Pt–Ni_x/CdS photocatalyst. Photocatalytic hydrogen production was carried out using a 300 W Xe light equipped with a 420 nm cut-off filter. The H₂ evolution rate of the Pt–Ni₃/CdS photocatalyst can reach a value as high as 48.96 mmol h⁻¹ g⁻¹ catalyst, with a quantum efficiency of 44.0% at 420 nm. The experimental results indicate that this Pt–Ni₃/CdS photocatalyst is a prospective candidate for solar hydrogen generation from water-splitting.

In this report, PtNi_x alloy NPs coupled with a CdS photocatalyst for photocatalytic hydrogen generation under visible light have been explored.