Synergistic effect of Au–Ag nano-alloying: intense SEIRA and enhanced catalysis

Abstract

The well-known AuAg nanohybrid system was effectively synthesized, utilizing polyvinyl pyrrolidone (PVP) as a multiple metal precursor reducing agent (based solely on their reduction potentials), thereby drastically decreasing their activation energy of diffusion and readily facilitating the homogenous alloy nanoparticle formation, duly confirmed by Vegard's law. Furthermore, the crucial parameters in determining the local electric field enhancement in the vicinity of the alloy nanoparticles such as the quality factor Q, dephasing time, T and the homogenous line width Γ were also evaluated in a systematic manner, in correlation with their unique visible optical absorption spectra. Optical band gap calculations of this robust AuAg/PVP nanocomposite system demonstrate the formation of trap levels between the HOMO and LUMO energy states with increasing Urbach's energy for decreasing Au content. The surface enhanced infrared (SEIRA) measurements with the analyte bromophenol, not only highlight the differential metal-PVP-analyte binding, but also corroborate the optical constants of the nanohybrids. Moreover, the catalytic conversion of 4-nitro-aniline (4-NA) to p-phenylenediamine (p-PDA) in the presence of AuAg nanohybrids visibly distinguishes their excellent stability and reproducibility along with their moderate rate constant in direct contrast to the poor recycling ability of their individual metal counterparts.

Mechanism of Gold–Silver Alloy Nanoparticle Formation by Laser Coreduction of Gold and Silver Ions in Solution

“…9−11 Aside from sensing applications, Au−Ag NPs may be utilized as antibacterial agents 12−14 and chemical catalysts. 15,16 Au−Ag NPs are typically synthesized with the reducing agent NaBH 4 and capping agents such as oleylamine, dodecylamine, and dodecanethiol. 17−21 However, NaBH 4 and other commonly used reductants such as hydrazine are toxic, and a volume of reducing agent that is greater than the stoichiometric requirement leaves an excess of toxic chemicals in the products, preventing their use in environmental and biological applications.…”

“…Thus, a changing chemical and physical environment may be sensed with Au–Ag NPs of certain Au and Ag compositions. Incorporating Ag into Au NPs was found to enable selective sensing of volatile organic compounds. , Au–Ag nanoprobes have been used to detect a DNA sequence from genes linked to cancer development, and Au–Ag nanoprobes of differing Au and Ag compositions may enable detection platforms for multiple nucleic acids. − For biological sensing using surface-enhanced Raman spectroscopy (SERS), Au–Ag nanoalloys would be ideal because they have a much narrower and stronger SPR peak than pure Au NPs and are much more stable than pure Ag NPs. − Aside from sensing applications, Au–Ag NPs may be utilized as antibacterial agents − and chemical catalysts. , …”

Summerfield scaling model and electrical conductivity study for understanding transport mechanisms of a Cr3+ substituted ZnAl2O4 ceramic

“…Using the extrapolation function F ( θ ), the true value of the lattice parameter ( a 0 ) was obtained by plotting the a experimental values of each diffraction peak as a function of the Nelson–Riley function to minimize systematic and random errors: 39 …”

Recent advances in gold nanoparticles for biomedical applications: from hybrid structures to multi-functionality

“…There are several alloyed plasmonic NPs (e.g. Au-Ag, 81,82 Au-Cu, 83 and Au-Pd 84 ), but they show little changes in e r , and therefore exhibit limited sensitivity enhancement. Recently, this approach has been achieved by increasing the material complexity (Section 2.2, from top to bottom in the framework in Fig.…”