Simple synthesis and size-dependent surface-enhanced Raman scattering of Ag nanostructures on TiO2 by thermal decomposition of silver nitrate at low temperature

Antimicrobial activity of silver-carbon nanoparticles on the bacterial flora of bull semen

The spermicidal effects of silver nanoparticles (AgNPs) hinder its application in the field of artificial insemination. In this study, silver-carbon NPs (Ag@C NPs) was synthesized and applied as an alternative antibiotic agent for bull semen extender. Ag@C NPs were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption flame spectroscopy, transmission electron microscope (TEM), and high-resolution TEM (HR-TEM). Data analysis revealed the successful synthesis of Ag@C NPs with a particle size of 1-5 nm (average particle size of 2.5 nm) embedded into carbon. The antimicrobial activity of Ag@C NPs was tested against bacteriospermia of fresh semen collected from five fertile bulls (three ejaculates/bull). Escherichia coli (E. Coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) were isolated from fresh semen samples and identified by culture, staining, and conventional biochemical tests. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Ag@C NPs against bacteriospermia was determined at 5 and 37 °C. Ag@C NPs showed efficient antimicrobial activity (MIC: 3.125-12.5 μg/mL) against the tested strains and strong bactericidal effect on S. aureus, and P. aeruginosa (MBC: 3.125 μg/mL), with no detrimental effect (P ˃ 0.05) on the percentage of sperm motility (70.71 ± 4.82; 74.65 ± 4.46), plasma membrane integrity (68.39 ± 4.31; 72.38 ± 4.91), acrosome integrity (88.40 ± 13.21; 86.77 ± 14.23), and normal sperm morphology (86.85 ± 7.43; 87.82 ± 8.15) at concentrations of 15 and 30 μg/mL, respectively, after a cold storage of 48 h. However, Ag@C NPs showed a detrimental effect on sperm parameters in a dose dependent manner at concentrations ≥60 μg/mL. Ag@C NPs showed no adverse effect on the sperm's ultrastructure with limited sperm internalization at MIC. In conclusion, Ag@C NPs could be used as an alternative antibiotic agent for bull semen extender without a significant cytotoxic effect on the sperm during cold storage. However, further investigations for their effects on embryo production and female genitalia are still required.

In situ preparation of Ag nanoparticles on silicon wafer as highly sensitive SERS substrate

An intensive surface enhanced Raman scattering (SERS) effect is realized by ordered Ag nanoparticles (NPs) in situ grown on silicon wafer directly using (3-aminopropyl) trimethoxysilane (APS) as both the surface modifier and reducing agent. The as-prepared ordered Ag NPs based SERS substrate shows excellent performance in detecting glycerin (an important integration in liquid super lubricating system) as well as conventional Rhodamine 6G (R6G, a kind of dye organic pollutant). The enhancement factor (EF) achieves 4-fold for glycerin and 10-fold for R6G (allowing for detecting as low as 10-11 M aqueous R6G), confirming the high sensitivity. The limited relative standard deviations (RSD) of the enhancement factors are within 15% for both glycerin and R6G, indicating the excellent uniformity. This remarkable progress is ascribed to the advantages of APS in improving adsorption and modulating distribution of Ag NPs on silicon, which results in a large local electric field to enhance the Raman signals. The SEM and UV-visible absorption spectrum characterization verified the contribution of APS in SERS improvement by investigating the influence of APS content and reduction time during the preparation process. All these advances imply that the SERS substrates prepared by Ag NPs in situ grown on silicon wafer have great potential application in real-time interface state tracing and sensitive detection.

Vibrational spectroscopic and bond valence study of structure and bonding in Al2O3-containing AgI–AgPO3 glasses

We present a detailed investigation of the effects of synthesis conditions on glasses xAgI–(1 − x)AgPO₃ with 0 ≤ x ≤ 0.4.

Controlled photocatalytic growth of Ag nanocrystals on brookite and rutile and their SERS performance

Ag nanocrystals (NCs) were photocatalytically grown on the surfaces of brookite and rutile nanocrystals, respectively, and their surface-enhanced Raman scattering (SERS) performance was evaluated. The resultant Ag NCs exhibit different morphologies owing to the different photocatalytic capabilities of the two types of TiO2 under otherwise identical synthetic conditions. The effects of AgNO3 concentration, UV irradiation time, and UV light power on the morphology evolution and growth kinetics of the Ag NCs were systematically investigated. Moreover, PVP was found to serve as both a reductant and a capping agent in the photocatalytic reaction systems, and its presence allows morphological control of the Ag NCs. A proper amount of PVP was confirmed to favor Ag nanoplates of larger sizes and to produce SERS substrates of substantially better performance.

Ag-decorated TiO₂ nanograss for 3D SERS-active substrate with visible light self-cleaning and reactivation

The production of SERS-active substrates which are uniform, sensitive, reproducibile and durable still remains an important issue. Here, we report a strategy for the fabrication of a large-area Ag-decorated TiO₂ nanograss SERS-active substrate by a simple solvothermal approach combined with Ag evaporation. The nanograss consists of dense rutile TiO₂ nanorods of about 5 nm in diameter and the decorated Ag nanoparticles are an average of 8 nm in diameter. The Ag protrusions and gaps between them contribute to three dimensional SERS "hot spots" which can be modulated by simply controlling the Ag evaporating parameters. The Ag-decorated TiO₂ substrate is highly efficient in detecting rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP) molecules and has good homogeneity. An obvious red shift and even high enhancement of b₂ vibration mode were observed in detecting 4-ATP due to the effective charge transfer from the Ag atoms to sulfur atoms. The Ag-decorated TiO₂ substrate can be easily self-cleaned and reactivated by visible light irradiation without obvious degeneration of SERS signals. Our results demonstrate that the Ag-decorated TiO₂ substrate with high and homogeneous SERS activity has potential feasibility as a sensitive SERS probe.

The effect of size and size distribution on the oxidation kinetics and plasmonics of nanoscale Ag particles

We employed a simple and effective electroless (EL) plating approach to produce silver nanoparticles (NPs) on bare silicon, on dielectric ZnO nanowires (NWs) and on Si NWs, respectively. The surface stability of the homogeneous Ag NPs formed on the ZnO NW surfaces was investigated by surface enhanced Raman spectroscopy (SERS), which show that the attachment of thiol to the Ag surface can slow down the oxidation process, and the SERS signal remains strong for more than ten days. To further examine the Ag NP oxidation process in air, the oxygen content in the silicon nanowire core/Ag sheath composites was monitored by the energy dispersive x-ray (EDX) method. The amount of oxygen in the system increases with time, indicating the silver NPs were continuously oxidized, and it is not clear if saturation is reached in this time period. To investigate the influence of the Ag NPs size distribution on the oxidation process, the oxygen amount in the NPs formed by EL deposition and e-beam (EB) evaporation on a bare silicon surface was compared. Results indicate a faster oxidation process in the EL formed Ag NPs than those produced by EB evaporation. We attribute this observation to the small diameter of the EL produced silver particles, which results in a higher surface energy.