Hydrothermal Synthesis of Ag Thin Films and Their SERS Application

In this article, a facile, one-step method for the formation of silver thin-film nanostructures on the surface of Al2O3 substrates using the hydrothermal method is proposed. The dependence of the SERS effect intensity of the formed films during the detection of methylene blue (MB) low concentrations on the synthesis conditions, additional temperature treatment, and laser radiation wavelength (532 and 780 nm) in comparison with similar dye films on commercial SERS substrates is shown. The detection limit of the analyte used for the indicated lasers is estimated. The effect of the synthesis temperature on the particle size, crystal structure, and microstructure features of the obtained thin films based on silver nanoparticles is demonstrated. Using spreading resistance microscopy, the interface between the substrate and Ag particles is studied, and the dependence of the size of the corresponding gap between them and the nature of microstructural defects on the parameters of hydrothermal treatment of reaction systems in the presence of Al2O3 substrates is shown. As a result of the study, the factors associated with the properties of the obtained SERS substrates and the parameters of recording the spectra, which affect the amplification factor of the spectral lines intensity of the analyte, are revealed.

Novel Approach to Synthesize Nanostructured Gallium Oxide for Devices Operating in Harsh Environmental Conditions

The importance of Ga2O3-based material for harsh environmental applications has attracted the interest of researchers in exploring various fabrication and growth techniques of Ga2O3-based nanomaterials using effective and low-cost processes. Herein, a demonstration to improve the wettability of liquid gallium on a rough silicon surface is presented. To control the roughness process, the silicon surface was patterned and groove-shape structures on the silicon were created using a photoelectrochemical (PEC) etching technique. Gallium oxide nanostructures were grown by thermal oxidation from liquid Ga in the presence and the absence of a silver thin film used as a catalyst. Scanning Electron Microscopy (SEM) was used to observe the morphology of the nanostructures grown on the roughed surface of the silicon substrate. The conformal deposition of Ga2O3 nanostructures inside the grooves of the PEC etched silicon surface was observed. The presence of Ag catalyst was found to completely change the morphology of Ga2O3. This method is recommended for the sustainable and low-cost synthesis of nanostructured gallium oxide for applications, including gas sensing.

Non-perpendicular incidence angle of cold atmospheric-pressure plasma treatment for fabrication of silver-based surface plasmon resonance biosensor for detection of Escherichia coli in water

In this study, for the first time, to our knowledge, a biosensor was produced using cold atmospheric plasma (CAP) treatment of silver thin film surface with non-perpendicular incidence angle for identification of Escherichia coli in the distilled water. Field emission scanning electron microscopy (FESEM) exhibits that before deposition, non-perpendicular CAP treatment of glass surface substrate leads to the production of pinhole-free silver thin film. The results of atomic force microscopy (AFM), and curve fitting show that non-perpendicular CAP treatment of this pinhole-free silver thin film indicates to the appearance of Ag NPs with smaller size and larger surface area compared to untreated silver film deposited on the untreated glass substrate. The silver-based pinhole-free SPR biosensor produced with non-perpendicular CAP treatment of both glass substrate and silver film shows E. coli detection in the distilled water in the range of 104 Colony forming unit (CFU/ml) to 108 CFU/ml with better sensitivity compared to the untreated silver-based SPR biosensor.

Synthesis of Nanoporous Gold by Chemical Dealloying of Co-Sputtered Gold-Silver Thin Films and Study of Its Variability

In the past two decades, nanoporous metals have attracted wide attention in the areas of energy storage, biomedicine and catalysis. Compared to other metals, nanoporous gold exhibits superior chemical stability, high catalytic activity, and its synthesis is facile and well documented. While many studies elaborate on the dealloying kinetics to understand process-structure relationships, its process variability is known to be large and yet not well documented. In this study, nanoporous gold was synthesized by chemical dealloying of co-sputtered gold-silver thin film. By controlling temperature and time during dealloying, its porosity characteristics, such as ligament diameter and solid area fraction, were controlled. Further, the time evolution of structural and elemental characteristics of nanoporous gold were examined including its correlation to silver residual content. It is found that mean diameters grow as a function of etch time from 25 to 60 nm. The large standard deviation (18.6 nm) of multiple dealloying attempts at any given temperature and dealloying time points to the lack of control in the kinetics of the dealloying reaction and variability in its substrate preparation and processing protocols. A comprehensive analysis of these parameters might provoke a better understanding of nanoporous gold synthesis in terms of the structure evolution kinetics.

Monitoring of the Environmental Corrosivity in Museums by RFID Sensors: Application to Pollution Emitted by Archeological Woods

The control of air quality in museums or storages is of fundamental interest for the conservation of historic artifacts. The present work reports an example of application of RFID sensors developed in the European project SensMat and dedicated to this issue. The sensors are based on the variation of property of an RFID tag coupled with a sensitive silver thin film exposed to the environment. As it will be described in the paper, such low-cost sensors are interrogated by a commercial reader and provide the environmental corrosivity index and thus the presence of pollutants. The selected case study concerns the monitoring of pollution by H2S in a building dedicated to conservation and restoration of archeological and historical woods. The ability of sensors to map spatially the corrosivity within buildings is highlighted.

Monitoring of the Environmental Corrosivity in Museums by RFID Sensors: Application to Pollution Emitted by Archeological Woods

The control of air quality in museums or storages is of fundamental interest for the conservation of historic artifacts. The present work reports an example of application of RFID sensors developed in the European project SensMat and dedicated to this issue. The sensors are based on the varia-tion of property of an RFID tag coupled to a sensitive silver thin film exposed to the environment. As it will be described in the paper, such low cost sensors are interrogated by a commercial reader and provide the environmental corrosivity index and thus the presence of pollutants. The selected case study concerns the monitoring of pollution by H2S in a building dedicated to conservation and restoration of archeological and historical woods. The ability of sensors to map spatially the corrosivity within buildings is highlighted.