RESUMEN
Surface Enhanced Raman Spectroscopy (SERS) could be a powerful technique for detecting trace gaseous sulfur-mustard, but it is still challenging due to the difficulty in efficiently capturing sulfur-mustard molecules by normal SERS substrates. Here, a chemically trapping strategy is presented for such detection via coating an ultrathin metal-oxide sensing layer on a SERS substrate. In the strategy, a SERS substrate Au-wrapped Si nanocone array is designed and fabricated by Si wafer-based organic template-etching and appropriate Au deposition, and coated with an ultrathin CuO for chemically capturing sulfur-mustard molecules. The validity of such strategy has been demonstrated via taking the gaseous 2-chloroethyl ethyl sulfide (a simulant of sulfur-mustard, or 2-CEES for short) as the target molecules. The response of the CuO-coated SERS substrate to the gaseous 2-CEES is detectable within 10 min, and the lowest detectable concentration is 10 ppb or less. Further experiments have shown that there exists an optimal CuO coating thickness which is about 6 nm. The CuO coating-based capture of 2-CEES molecules is attributed to the surface hydroxyl-induced specific adsorption, which is subject to the pseudo-second-order kinetics and Freundlich-typed model. This study presents the practical SERS chips and new route for the trace detection of gaseous sulfur-mustard.
RESUMEN
This paper mainly presents a facile and cost-effective method to achieve large-scale ZnO nanocap (ZnO NC)-ordered arrays with a controllable amount of Au nanoparticles (Au NPs) decorated on their surface. The preparation process includes the construction of polystyrene nanosphere (PS) mask, metal deposition, and annealing process. The Au NPs/ZnO NCs have apparent hierarchical structure. Interestingly, the size and number of Au NPs can be controlled by changing the time of Au deposition and the diameter of PSs. Moreover, the Au NP/ZnO NC arrays can be used as a substrate to detect harmful dye molecules based on surface-enhanced Raman scattering (SERS) effect, and show ultrahigh sensitivity with a limit of detection (LoD) of 10-10 M for crystal violet (CV) molecules. In addition, the above substrate has achieved reusable detection due to their excellent photocatalytic degradation performance for harmful molecules. The finite difference time-domain (FDTD) simulation results have revealed that SERS "hot spots" are almost distributed at the junctions of Au NPs and ZnO NCs. The above results show that the composite substrates have a good prospect in practical applications in the future.
RESUMEN
Surface enhanced Raman spectroscopy (SERS) is a new and developing analytical technology in chemical and biological detection. However, traditional hard SERS substrates are struggling to meet the growing demand for flexible devices. In this work, we introduce a simple, cost-effective and large scale preparation route to form a flexible Au nanocap (AuNC) ordered array as SERS substrates via reactive ion etching (RIE) method and then Au deposition. We find RIE is an excellent method for nanoroughening the surface of polystyrene (PS) spheres. Such flexible SERS substrates exhibit high sensitivity and uniformity for detecting organic molecules. The finite-difference time-domain simulation results revealed that a strong electric field coupling effect existed not only in the gap site between the Au nanoparticles (AuNPs), but also in the connection position between the AuNCs and the single AuNP. This study not only offers a novel way for nanoroughening of PS spheres, but also acquires flexible and cheap SERS substrates for quick and sensitive detection of organic molecules.
