Ting Chu Hsu

Strategy to improve stability of surface-enhanced raman scattering-active Ag substrates

Surface-enhanced Raman scattering (SERS)-active Ag substrates were popularly employed for evaluating the structural situation of analytes because SERS-active Ag substrates can demonstrate more significant SERS effects than Au and Cu substrates. However, the stability of SERS-active Ag substrates is an issue of concern in their application. In this work, SERS-active modified Ag substrates were simply prepared in 0.1 N HCl solutions containing Al2O3 nanoparticles by electrochemical methods. Experimental results indicate that the Al2O3-modified Ag substrate can significantly improve its thermal stability by raising the operation temperature of the Ag substrate by over 100 °C. Moreover, the aging of SERS enhancement capabilities in an atmosphere of 50% relative humidity (RH) and 20% (v/v) O2 at 30 °C is markedly depressed based on this Al2O3-modified Ag substrate.

Size-controllable synthesis of surface-enhanced Raman scattering-active gold nanoparticles coated on TiO2

As shown in the literature, gold nanoparticles (NPs) were popularly used in the fields of catalyst and surface-enhanced Raman scattering (SERS). In this work, size-controllable Au NPs coated on TiO(2) are synthesized by adjusting the pH of solutions based on sonoelectrochemical methods. The size-controlled Au NPs on TiO(2), ranging from 2 to 80 nm in diameter, can be obtained by varying the pH of solutions from 3 to 7 and placing the sample for 3 h before sonoelectrochemical reductions. The optimal particle sizes of Au NPs on TiO(2) to obtain the strongest SERS effects under an irradiation of 785 nm for probe molecules of adsorbed Rhodamine 6G (R6G) and deposited polypyrrole (PPy) are all ca. 60 nm.

New pathway to prepare gold nanoparticles and their applications in catalysis and surface-enhanced Raman scattering

As shown in the literature, additional energies are necessary for the reduction of positively charged noble metal ions to prepare metal nanoparticles (NPs). In this work, we report a new green pathway to prepare Au NPs in neutral 0.1M NaCl aqueous solutions from bulk Au substrates without addition of any stabilizer and reductant just via aid of natural chitosan (Ch) at room temperature. Au- and Ch-containing complexes in aqueous solution were electrochemically prepared. The role of Ch is just an intermediate to perform electron transfer with Au NPs. The stability of these prepared Au NPs is well maintained by Au NPs themselves with slightly positively charged Au remained on the surface of Au NPs. The particle size of prepared spherical Au (111) NPs is ca. 15 nm in diameter. Moreover, increasing the pH of preparation solutions can be contributive to preparing concentrated Au NPs in solutions. The prepared Au NPs are surface-enhanced Raman scattering (SERS)-active for probe molecules of Rhodamine 6G. They also demonstrate significantly catalytic activity for decomposition of acetaldehyde in rice wine.

Improved stabilities on surface-enhanced Raman scattering-active Ag/Al2O3 films on substrates

As is shown in the literature, surface-enhanced Raman scattering (SERS)-active Ag films obtained by the salting-out of Ag colloids from solutions with some salts, are popularly used to examine the structure of analytes. SERS-active Ag nanoparticles (NPs) demonstrate more significant SERS effects than Au NPs, however, problems regarding the stabilities of SERS-active Ag NPs remain to be overcome. In this work, Ag/Al(2)O(3) colloids were prepared in 0.1 M HNO(3) solutions containing Al(2)O(3) NPs with higher heat capacity by sonoelectrochemical methods. SERS-active Ag/Al(2)O(3) films deposited on glass slides were prepared by the addition of a saturated NaCl solution in the prepared Ag/Al(2)O(3) colloids-containing solution. In an acceptable sacrifice of Raman intensity by ca. 30% magnitude, the prepared Ag/Al(2)O(3) films markedly improved thermal stability by raising the operation temperature over 100 °C, compared to Ag films. Meanwhile, aging of SERS enhancement capability in an atmosphere of relative humidity (RH) of 50% and 20% (v/v) O(2) at 30 °C is significantly depressed using Ag/Al(2)O(3) films.

New electrochemical method to deposit surface-enhanced Raman scattering-active silver nanoparticles on metal substrates

As shown in the literature, many methods have been developed to improve the signal, reproducibility and stability of surface-enhanced Raman scattering (SERS) for its reliable application. However, the fabrication needed is laborious. In this work, we propose an effective method to prepare SERS-active substrates with Ag nanoparticles (NPs) by a new electrochemical strategy of deposition–dissolution cycles (DDCs). This electrochemical method is based on a cathodic potential of 0.25 V and an anodic potential of 1.05 V vs.Ag/AgCl, which are applied in turn under sonication. The prepared SERS-active substrate demonstrates a large Raman scattering enhancement for adsorbed Rhodamine 6G (R6G). The practical detection limit for polypyrrole deposited on this substrate is 0.1 μC cm−2. Moreover, the prepared SERS-active substrates exhibit satisfactory reproducibility and thermal stability. The SERS spectrum of R6G on the newly developed substrate still performs well at a high temperature of 250 °C.