Tailoring gold and silver colloidal bimetallic nanoalloys towards SERS detection of rhodamine 6G

Nanoparticles of gold, silver and their bimetallic alloys were tailored for SERS sensing towards trace amounts of rhodamine 6G.

Large-scale uniform Au nanodisk arrays fabricated via x-ray interference lithography for reproducible and sensitive SERS substrate

Large-scale Au nanodisk arrays on Si substrate are successfully fabricated via x-ray interference lithography and followed by electron-beam vapor deposition. The Au nanodisk arrays exhibit a significant, uniform, and reproducible surface enhancement on Raman scattering signal, which enables the detection of R6G as low as 10(-8) M with an enhancement factor of 10(6). Importantly, the Au nanodisk arrays SERS-active substrates with uniformly high sensitivity also have high reproducibility and stability. The diameters of the nanodisks and the inter-disk distance can be simply optimized to obtain high enhancement in Raman signal by varying exposure time and development time in XIL process. The electric fields of the Au nanodisks with various diameters and inter-disk distance simulated by the finite difference time domain (FDTD) techniques further confirm that the Raman signal enhancement of Au nanodisks is determined by the diameters of nanodisks and the inter-disk distance of nanodisks. The Au/Ag double-layer bimetal nanodisk arrays are also fabricated which show a significant increase in the Raman signal enhancement than that of the Au nanodisk arrays. XIL nanofabrication appears to be a feasible approach to prepare uniform and reproducible SERS-active substrates with high sensitivity for practical SERS applications.

Real-time monitoring of oxidative burst from single plant protoplasts using microelectrochemical sensors modified by platinum nanoparticles

Oxidative bursts from plants play significant roles in plant disease defense and signal transduction; however, it has not hitherto been investigated on individual living plant cells. In this article, we fabricated a novel sensitive electrochemical sensor based on electrochemical deposition of Pt nanoparticles on the surface of carbon fiber microdisk electrodes via a nanopores containing polymer matrix, Nafion. The numerous hydrophilic nanochannels in the Nafion clusters coated on the electrode surface served as the molecular template for the deposition and dispersion of Pt, which resulted in the uniform construction of small Pt nanoparticles. The novel sensor displayed a high sensitivity for detection of H(2)O(2) with a detection limit of 5.0 x 10(-9) M. With the use of this microelectrochemical sensor, the oxidative burst from individual living plant protoplasts have been real-time monitored for the first time. The results showed that oxidative burst from single protoplasts triggered by a pathogen analogue were characterized by quanta release with a large number of "transient oxidative microburst" events, and protoplasts from the transgenic plants biologically displayed better disease-resistance and showed a distinguished elevation and longer-lasting oxidative burst.

SERS-active Ag/Au bimetallic nanoalloys on Si/SiO(x)

Nanoalloys are clusters formed of two or more metallic elements and are of interest for applications in catalysis, spectroscopy, photonics, electronics, and magnetism. The hybridization of the individual plasmonic absorptions of different alloyed metals allows for plasmon tunability and a better coupling of plasmon-excitation line, giving rise to significant increases in the enhancement factor for surface-enhanced Raman scattering (SERS) spectroscopy. Here we report simple fabrication procedures for the preparation of Ag/Au nanoalloys on Si/SiO(x) substrates, with tunable plasmon resonances. The mechanism and kinetic of the nanoalloy formation and its optical properties were studied by SEM, XPS, SPR, and SERS.

SERS study of the controllable release of nitric oxide from aromatic nitrosothiols on bimetallic, bifunctional nanoparticles supported on carbon nanotubes

A hybrid system comprising bimetallic nanoparticles supported on carbon nanotubes (CNTs) was engineered to maximize the surface-enhanced Raman scattering signal from solution by generating a high density of hot spots with reproducible enhancing activity and long-term colloidal and optical stability. CNT@AgAu was employed as a bifunctional material to catalyze and monitor the controlled release of nitric oxide from aromatic nitrosothiols, as a function of the gold content.

Gold Nanoparticle Based Surface Enhanced Fluorescence For Detection of Organophosphorus Agents

Organophosphorus agents (OPA) represent a serious concern to public safety as nerve agents and pesticides. Here we report the development of gold nanoparticle based surface enhanced fluorescence (NSEF) spectroscopy for rapid and sensitive screening of organophosphorus agents. Fluorescent from Eu3+ ions that are bound within the electromagnetic field of gold nanoparticles exhibit a strong enhancement. In the presence of OPA, Eu3+ ions are released from the gold nanoparticle surface and thus a very distinct fluorescence signal change was observed. We discussed the mechanism of fluorescence enhancement and the role of OPA for fluorescence intensity change in the presence of gold nanoparticles.