Growth Of Silver Shell Research Articles

In situ monitoring PUVA therapy by using a cell-array chip-based SERS platform

Psoralen ultraviolet A (PUVA) therapy has thrived as a promising treatment for psoriasis. However, overdose of PUVA treatment will cause side-effects, such as melanoma formation. And these side-effects are often ignored during PUVA therapy. Hence, in situ monitoring therapeutic response of PUVA therapy is important to minimize side-effects. Aberrant expression of tyrosinase (TYR) has been proved to be associated with melanoma, indicating that TYR is a potential target for evaluation of PUVA therapy. Herein, we reported a strategy for in situ monitoring TYR activity during PUVA therapy by using a cell-array chip-based SERS platform. The cell-array chip was used to simulate cell survival environment for cell culture. Capture of single cells and living cell analysis were realized in the isolated microchambers. An enzyme-induced core-shell self-assembly substrate was used to evaluate TYR activity in living cells during PUVA therapy. The gold nanoparticle modified with a SERS reporter, 4-mercaptobenzonitrile (4-MBN), was used as the core. In the presence of oxygen and TYR, hydroxylation of l-tyrosine occurred, leading to the reduction of silver ion on the surface of gold cores. The growth of silver shells was accompanied by the increased SERS intensity of the reporter, which is related directly to TYR activity. The detection limit for TYR activity is 0.45 U/mL. Upregulation of TYR activity was successfully monitored after PUVA therapy. Notably, real-time and in situ information of therapeutic response can be obtained through monitoring PUVA therapy by using a cell-array chip-based SERS platform, which has great potential to guide the clinical application of PUVA therapy.

Unravelling the Mechanisms of Gold-Silver Core-Shell Nanostructure Formation by in Situ TEM Using an Advanced Liquid Cell Design.

The growth of silver shells on gold nanorods is investigated by in situ liquid cell transmission electron microscopy using an advanced liquid cell architecture. The design is based on microwells in which the liquid is confined between a thin Si3N4 membrane on one side and a few-layer graphene cap on the other side. A well-defined specimen thickness and an ultraflat cell top allow for the application of high-resolution TEM and the application of analytical TEM techniques on the same sample. The combination of high-resolution data with chemical information is validated by radically new insights into the growth of silver shells on cetrimonium bromide stabilized gold nanorods. It is shown that silver bromide particles already formed in the stock solution play an important role in the exchange of silver ions. The Ag shell growth can be directly correlated with the layer-by-layer dissolution of AgBr nanocrystals, which can be controlled by the electron flux density via distinctly generated chemical species in the solvent. The derived model framework is confirmed by in situ UV-vis absorption spectroscopy evaluating the blue shift in the longitudinal surface plasmon resonance of anisotropic NRs in a complementary batch experiment.

Fabrication of Silver Shells onto Silica Sphere for Infrared Emissivity

SiO2/Ag core-shell composite microspheres were synthesized by silver-seeding method in this paper. In the process, silver nanoparticles as seeds were deposited by repeating the cycle times for further formation of Ag shell. The effects of reaction power and time on the seeding of silica surfaces and the effect of silver ion on the growth of silver shells were investigated. Structures and properties were measured with TEM, UV, FT-IR and Infrared emissometer. The results showed the Ag nanoparticles on the silica surfaces were uniform in size. And the number density was increased growing with the increase of deposition. It was found that the composite exhibited a lower infrared emissivity value in the wavelength range from 8 to 14 μm than that of pure silica as a result of strong reflection of silver metal.

Synthesis of hollow silver spheres using poly-(styrene-methyl acrylic acid) as templates in the presence of sodium polyacrylate

Hollow silver spheres were successfully prepared by reducing AgNO 3 with ascorbic acid and using negatively charged poly-(styrene-methyl acrylic acid) (PSA) spheres as templates in the presence of sodium polyacrylate as a stabilizer. Firstly, silver cations adsorbed on the surface of PSA spheres via electrostatic attraction between the carboxyl groups and silver cations were reduced in situ by ascorbic acid. The silver nanoparticles deposited on the surface of PSA spheres served as seeds for the further growth of silver shells. After that, extra amount of AgNO 3 and ascorbic acid solutions were added to form PSA/Ag composites with thick silver shells. In order to obtain compact silver shells, the as-prepared PSA/Ag composites were heated at 150 °C for 3 h. Then hollow silver spheres were prepared by dissolving PSA templates with tetrahydrofuran.

Preparation of spindle-shape silver core-shell particles

Silver core-shell nanoparticles with spindle shape were successfully synthesized by the seed-mediated growth technique. Small amount of silver nanoparticles (4±1.5 nm) were immobilized on polyethylene amine (PEI) coated spindle-shape β-FeOOH particles and served as ‘seeds’ for further growth of silver shell. The seed catalyzed growing process was repeated for 1 to 4 times, the surface coverage of the silver core-shell particles was increased until a complete silver layer was formed finally. UV–visible extinction spectra showed that two absorption peaks red-shifted with the increasing surface coverage and shell completeness. Our research showed that these spindle-shape silver core-shell particles were promisingly to be used as surface enhanced Raman scattering (SERS) nanosensors.