Preparation and characterization by surface-enhanced infrared absorption spectroscopy of silver nanoparticles formed on germanium substrates by electroless displacement

Abstract

In this paper, the feasibility of applying electroless displacement to prepare silver nanoparticles (AgNPs) on the surface of germanium (Ge) substrate is demonstrated, and the performances of surfaces prepared in this manner for surface-enhanced infrared absorption (SEIRA) spectroscopy are reported. The process used to produce suitable AgNPs for SEIRA by electroless deposition is simple and effective, requiring only pretreatment of the germanium surface with hot air, immersion of the substrate in a dilute solution of silver nitrate, and washing of the resulting plate. To quantify the behavior of AgNPs on a Ge substrate and to optimize the conditions for the preparation of AgNPs on Ge substrates, a monolayer of p-nitrothiophenol (PNTP) was bonded to the surface of the AgNPs by immersion of the plate in a dilute solution of PNTP and measurement of the transmission spectrum. The factors that influenced the formation of AgNPs, and hence the SEIRA signals, included the concentration of AgNO3, the reaction time and the temperature. Results indicated that stronger absorption bands in the SEIRA spectrum of a monolayer of PNTP were obtained if the reaction rate for the displacement of silver ions by Ge was slow. This condition was achieved by keeping the concentration of AgNO3 and the reaction temperature low. Under the optimal conditions found in this work, an enhancement factor of approximately 100 was achieved for commonly used probe molecules in SEIRA measurements.

Facile fabrication of silver nanoparticles on silicon for surface‐enhanced infrared and Raman analysis

“…Reaction time is another important parameter that may deserve attention. Similar to that observed by Yang and Griffiths for the formation of Ag nanoparticles on Ge, [26] SEIRA signal from AgNP/Si initially increases with reaction time. However, when the reaction takes longer than 10 min, for example, in the solution containing 5 mM AgNO 3 and 60 mM HF, the AgNPs will start to form an unstable film and are inclined to peel off from the substrate.…”

“…For the latter, the main reaction [26] is regarded as 4Ag + + Ge = 4Ag + Ge 4+ , and for the former, as 4Ag + + 6F − + Si = 4Ag + SiF 6 2− used in the present work. The latter equation suggests that the formation of Ag nanoparticles may strongly depend upon the relative concentrations of Ag + and F − , and a higher concentration for F − is necessary.…”

“…[25] Recently, chemical deposition of Ag nanoparticles on IRtransparent substrates has received strong attention for fabricating SEIRA-active templates. [25,26] In fact, electroless displacement for preparing silver nanoparticles on Ge for SEIRA analysis has been reported by Yang and Griffiths, [26] which involved hotair pretreatment of a Ge disk to form a thin surface layer of germanium oxide followed by immersion in a dilute solution of silver nitrate. A conductive Ag film on the reflecting plane of a Ge prism was also chemically deposited by Rodes and his coworkers for electrochemical ATR-SEIRAS application.…”

Multilayer Structures of Self‐Assembled Gold Nanoparticles as a Unique SERS and SEIRA Substrate

“…However, the astonishing research interest manifested today concerning how to control, manipulate, and amplify light on the nanometer length scale by using the properties of the collective electronic excitations in noble-metal films or nanoparticles has prompted the resurgence not only of SERS, [4,[11][12][13][14][15][16][17] but also of SEIRA techniques. [18][19][20][21][22] The enhancement of both Raman and IR signals is of particular interest because of the efficiency of these spectroscopic methods in elucidating molecular structures and obtaining complete information on the adsorption behavior and orientation of molecular species. The experimental data accumulated in recent years have demonstrated that these spectroscopic methods are sufficiently sensitive for surface science, analytical and environmental applications, biomedicine, biophysics, and biochemistry.…”

Metal Nano Layer Coating for Improving the Detection and Recognition of Micro-Poisons Using Reflection Spectroscopic Measurement

“…An example of using metal nano particles in spectroscopic measurements is the Surface-Enhanced Infrared Absorption (SEIRA) method [18]. In this method, Silver nano particles on germanium substrate were used to enhance the MIR absorption in spectroscopic measurement.…”