Rhodamine depositions with

Figure 18 Graphs (Deng and Juang, 2014) demonstrating (A) SERS spectra of 10" mol/L concentration rhodamine-6G response intensity dependence on gold layer thickness that was deposited on the black silicon substrate. (B)The Raman spectra for 10" to 10" mol/L rhodamine-6G on the black silicon substrate deposited with 400-nm-thick gold layer.

The clear transition in the polarization behaviour that occurs at about 6 pM shows that the structure of the interface has changed. It is likely that this corresponds to reaching a critical packing density at which a change of phase takes place and the adsorbed layer corresponds to a collection of dye dimers at the interface. The formation of multiple layers has been observed with spin-coated films although multilayers of Rhodamine B have been deposited from solution without a change being observed in the layer structure. Similarly the predominance of dimers at interfaces has been inferred previously but in the current situation we are able to observe the transition between monomers and dimers at the interface. 

The multilayer coating of particles and formation of ultrathin microcapsules were verified by confocal laser scanning microscopy (CLSM, Leica) and atomic force microscopy (AFM, NanoScope). For AFM measurements, a drop of each sample was deposited onto the silicon support (with a PEl/PSS sublayer) and dried. For CLSM analysis, the coated particles and multilayer capsule suspensions were preliminary colored with rhodamin C. 

Rhodamine B isothiocyanate was adsorbed onto microcrystalline cellulose by two different methods deposition from ethanolic and aqueous solutions followed by solvent evaporation (Type I) and also fnim aqueous solutions in equilibrium with the powdered solid and following a dyeing protocol (Type II). Figure 38 displays the scheme of the dyeing procedure used to bind rhodamine molecules to microcrystalline cellulose [15]. 

Figure 3. Optical micrographs of glass slides showing the formation of silver islands after multiple depositions of Ag sol with ultrasonic sprayer (a) and (b) Substrates with Ag nanoparticles sprayed-on (c) adenine (d) Rhodamine 6G.

They have also used the same approach to detect TNT using capping silica nanoparticles (200 nm in diameter) with primary amine receptors and fluorescein or rhodamine dyes [126]. The analyte brings about induced quenching of the fluorescence for both species again via a FRET mechanism. Nanoparticle assembled chips were able to detect TNT in solution down to nanomolar concentrations while when deposited as a thin film could sense nitroaromatic vapours down to 4 ppb in air. 

---