Figure 2 TEM characterization. (A) TEM images of PEG-reduced AgNPs obtained by rapidly adding AgNO3 to the aqueous PEG solution. (B) Atomic-scale resolution TEM image of one PEG-reduced AgNP exhibiting the 5-nm PEG layer around the silver core. Spherical PEG-coated AgNPs of narrow size distribution are visible. SERS measurements The SERS activity of the as-produced PEG-coated AgNPs is an important issue for further biomedical

applications of these nanoparticles. Since both the citrate- and the hydroxylamine-reduced silver colloids are ones of the most used SERS substrates, they were chosen as a reference for the characterization of SERS activity of the PEG-reduced silver colloid. Figure 3 Salubrinal purchase shows SERS spectra of methylene blue and Cu(PAR)2 analytes obtained with PEG-, citrate-, and hydroxylamine-reduced silver sols using the 532-nm laser line. The concentrations of methylene blue and Cu(PAR)2 analytes were 1.0 × 10−6 and 1.25 × 10−5 M, respectively. In order to achieve a higher SERS enhancement for citrate-reduced silver colloids, 10 μl of NaCl (0.1 M) solution was added. This was not the case for the PEG-reduced silver colloid, suggesting that the Raman signal is enhanced only by the single PEG-coated AgNP positioned in the laser focus and not by aggregates through the so-called hot-spots. The lack of pure Raman signal of the analytes, at the same concentrations

as GSK1904529A manufacturer in the SERS spectra, supports the idea that the SERS signal is due to the presence of the PEG-coated nanoparticles. Figure 3 SERS U0126 molecular weight analysis of Cu(PAR) 2 and methylene blue. SERS spectra (employing the 532-nm laser line) of methylene blue adsorbed on (curve A) the rapid PEG-reduced

(peg_r), (curve B) the hydroxylamine-reduced (hya), and (curve C) the citrate-reduced (cit) silver sol and of Cu(PAR)2 adsorbed on (curve D) the rapid PEG-reduced (peg_r), (curve E) the dropwise PEG-reduced (peg_s), (curve F) the hydroxylamine-reduced (hya), and (curve G) the citrate-reduced (cit) silver sol. The spectra were shifted for check details clarity. Specific vibrational peaks of analyte molecules are clearly visible for all three classes of silver colloids. The general applicability of the PEG-reduced silver sol is further checked by recording the SERS spectra of amoxicillin and p-aminothiophenol adsorbed on PEG-reduced silver sol, using both 532- and 633-nm laser lines (Figure 4). These spectra are then compared with those obtained on both the citrate- and the hydroxylamine-reduced silver colloid (Figure 4). The concentrations of amoxicillin and p-aminothiophenol analytes were 5 × 10−5 and 5 × 10−7 M, respectively. Figure 4 SERS analysis of p -aminothiophenol and amoxicillin. SERS spectra of p-aminothiophenol (patp) and amoxicillin (amx) adsorbed on PEG-reduced silver sol using both 633-nm (curves A and C) and 532-nm (curves B and D) laser lines. The spectra were shifted for clarity. Specific vibrational peaks of analytes molecules are clearly visible for all three classes of silver colloids.