Shape-diversified silver nanostructures uniformly covered on aluminium micro-powders as effective SERS substrates

New Trends in Nanoarchitectured SERS Substrates: Nanospaces, 2D Materials, and Organic Heterostructures

This article reviews recent fabrication methods for surface-enhanced Raman spectroscopy (SERS) substrates with a focus on advanced nanoarchitecture based on noble metals with special nanospaces (round tips, gaps, and porous spaces), nanolayered 2D materials, including hybridization with metallic nanostructures (NSs), and the contemporary repertoire of nanoarchitecturing with organic molecules. The use of SERS for multidisciplinary applications has been extensively investigated because the considerably enhanced signal intensity enables the detection of a very small number of molecules with molecular fingerprints. Nanoarchitecture strategies for the design of new NSs play a vital role in developing SERS substrates. In this review, recent achievements with respect to the special morphology of metallic NSs are discussed, and future directions are outlined for the development of available NSs with reproducible preparation and well-controlled nanoarchitecture. Nanolayered 2D materials are proposed for SERS applications as an alternative to the noble metals. The modern solutions to existing limitations for their applications are described together with the state-of-the-art in bio/environmental SERS sensing using 2D materials-based composites. To complement the existing toolbox of plasmonic inorganic NSs, hybridization with organic molecules is proposed to improve the stability of NSs and selectivity of SERS sensing by hybridizing with small or large organic molecules.

Highly Sensitive, Uniform, and Reusable Surface-Enhanced Raman Scattering Substrate with TiO₂ Interlayer between Ag Nanoparticles and Reduced Graphene Oxide

TiO2 nanoparticles and Ag nanoparticles were successively deposited on reduced graphene oxide (rGO) by a two-step solvothermal process to develop a reusable surface-enhanced Raman scattering (SERS) substrate with high sensitivity and uniformity owing to the 2-dimensional planar structure of rGO, the photocatalytic activity of TiO2, and the SERS function of Ag nanoparticles. The presence of TiO2 interlayer efficiently diminished the interference from the Raman intensities of D-band and G-band of rGO and hence enhanced the sensitivity significantly. As compared to Ag/rGO nanocomposite, the detection limit of 4-aminothiophenol (4-ATP) for Ag/TiO2/rGO nanocomposite could be lowered from 10(-10) to 10(-14) M, and its enhancement factor could be raised from 1.27 × 10(10) to 3.46 × 10(12). Meanwhile, good uniformity remained, the relative standard deviation (RSD) value was about 10%. Furthermore, by UV irradiation in water, the photocatalytic property of TiO2 could eliminate the Raman signal of 4-ATP efficiently and made this substrate reusable. After being reused five times, its excellent SERS performance was still retained. Thus, the Ag/TiO2/rGO nanocomposite developed in this work was a promising SERS substrate with good reusability and high sensitivity and uniformity.

Facile fabrication of a silver dendrite-integrated chip for surface-enhanced Raman scattering

A facile approach to fabricating a surface-enhanced Raman scattering (SERS)-active chip by integrating silver dendrites with copper substrate through a one-step process was explored. The structures of dendrites were synthesized and controlled by an AgNO3/PVP aqueous system, and the fabrication parameters amount of AgNO3/PVP and reaction time were systematically investigated. The optimized silver dendrites, closely aggregated on the surface of the copper chip, exhibited high SERS activity for detecting rhodamine 6G at a concentration as low as 3.2 × 10(-11) M. Meanwhile, the prepared SERS-active chip displayed a high thermal stability and good reproducibility. Moreover, the potential application for analysis of polycyclic aromatic hydrocarbons was demonstrated by detection of fluoranthene at a low concentration of 4.5 × 10(-10) M. This SERS-active chip prepared by the convenient and high-yield method would be a promising means for rapid detection under field conditions.

Facile synthesis of silver submicrospheres and their applications

Silver submicrospheres fabricated under an ambient condition can catalyze the reduction of 4-nitrophenol and improve significantly the Raman signal of crystal violet as surface-enhanced Raman scattering (SERS) substrate.