Template-Activated Strategy toward One-Step Coating Silica Colloidal Microspheres with Sliver

Abstract

Template-activated strategy was developed to coat silica (SiO2) colloidal microspheres with silver in one step, based on one-pot hydrothermal treatment of silver nitrate, PVP (poly(vinyl pyrrolidone)), and SiO2 colloidal microspheres in ammonia solution. In our reaction system, the surface of SiO2 colloidal microspheres was continually activated with negative-charged SiO(-) groups in ammonia solution, which accumulated [Ag(NH3)2](+) or Ag(+) ions around the SiO2 colloidal microspheres through electrostatic attraction; thereafter these ions could be reduced into Ag nanoparticles in situ by the weak reducer PVP in the solution, and then acted as seeds for the subsequent complete silver coating with the reaction proceeding. Therefore, the traditional three steps for complete silver coating, including prior surface modification, seeding, and subsequent growing, were effectively integrated into one step. The experimental results exhibited that perfect SiO2/Ag core/shell composite microspheres were successfully synthesized through optimizing the reaction parameters like the solvent ingredient, reducer, and the reaction temperature. Additionally, these obtained uniform composite microspheres were further used as SERS substrate by using R6G and thiram as probe molecules, and showed excellent trace detection of these organic chemicals in solution.

Fabrication of cube-like Fe3O4@SiO2@Ag nanocomposites with high SERS activity and their application in pesticide detection

“…The FSA composites were synthesized by coating the Ag nanoparticles onto the silica shell of the Fe 3 O 4 @SiO 2 composites: the functional groups on the surface of Fe 3 O 4 @SiO 2 composites were first activated to negative-charged -SiO -by ammonia in the hydrothermal condition (high temperature and pressure). (Wang et al 2014b). Thus, positive-charged [Ag(NH 3 ) 2 ] ?…”

Substrate-Immersed Solvothermal Synthesis of Ordered SiO2/Ag Arrays as Catalytic SERS Substrates

“…Here, the -OH on the surface of SiO 2 can be activated in ethanol, and Ag(NH 3 Þ þ 2 was rapidly absorbed to form silver ions layer by electrostatic forces. 15 After that, Ag (NH 3 Þ þ 2 was reduced by existing ethanol via simple solvothermal process. The absorption, nucleation and growth process were accomplished in the reactor directly.…”

Silica nanoparticle based techniques for extraction, detection, and degradation of pesticides

“…For on-site detection of this pesticide on fruit samples, the nanostructures (SiO 2 @Ag) could be coated on apple peels and Thiram at a concentration as low as 38 ng/cm 2 could be detected. Another report on SERS based detection of Thiram describes the use of Ag nanoparticles coated on to silica colloidal spheres via poly vinyl pyrrolidone [104]. An optofluidic SERS device involving the use of SiO 2 @Ag nanostructures for on-site analysis of Methyl parathion and Thiram from aquaculture settings has also been developed [105].…”