Probing a dip-coated layer of organic molecules by an aerosol nanoparticle sensor with sub-100 nm resolution based on surface-enhanced Raman scattering

Abstract

A surface coated with organic molecules has been probed by a sub 100 nm resolution particulate sensor by surface-enhanced Raman scattering (SERS) technique.

Electrospray surface-enhanced Raman spectroscopy (ES-SERS) for probing surface chemical compositions of atmospherically relevant particles

“…S6) of the aerosol from the electrospray. The size of Ag nanoparticles in suspension has been reported to be ∼ 50 nm (Gen and Lenggoro, 2015). The similarity in size between particles in the suspension, particles in the gas phase and particles deposited on the substrate Figure 4.…”

“…1b) using the electrospray technique (Gen and Lenggoro, 2015). An aqueous suspension of Ag nanoparticles was prepared by reducing silver nitrate with sodium citrate (Lee and Meisel, 1982).…”

“…Figure 2 shows the electrospray system consisting of a generation and a deposition chamber. The suspension was diluted with an equal volume of ethanol to reduce the surface tension and to facilitate the evaporation of solvents (Gen and Lenggoro, 2015). The diluted suspension was fed to a stainless-steel capillary tube (SUS304; 32 gauge, Hamilton) which serves as a spray nozzle using a syringe pump (KDS-100, KD Scientific) at a liquid flow rate of 0.2 mL h −1 .…”

“…The substrate was set perpendicular to the spray nozzle in the deposition chamber and negatively charged at −2.0 kV using another high-voltage module (HV2, S1-5N(A)-L2, Matsusada Precision Inc.). Ag nanoparticles were deposited on the substrate at ambient pressure (1 atm) and the spraying time was 1 h based on earlier work (Gen and Lenggoro, 2015). The Ag nanoparticles produced were electrically neutralized with a Kr-85 aerosol neutralizer (model 3077A, TSI Inc.) before entering the DMA for size distribution measurements.…”

“…A significant enhancement was observed only at the edge of particles likely due to spatially non-uniform SERS-active spots distributed across individual particles (Craig et al, 2015). Gen and Lenggoro (2015) recently developed an SERS approach to probe surfaces coated with an organic thin film by electrospraying Ag nanoparticle aerosols over the probed surfaces (Gen and Lenggoro, 2015). A number concentration of 11.6 particles µm −2 and a narrow distribution of separa- tion distance between deposited particles peaking at 100 nm confirmed the concentrated and uniform deposition pattern of Ag nanoparticles on a substrate, respectively.…”