Micro‐nanofabrication technologies are frequently used to prepare surface‐enhanced Raman scattering (SERS)‐active substrates with specially shaped microstructures, whose characteristics of high sensitivity and good reproducibility are our unswerving pursuit of the goal. However, these techniques suffer from high cost and low throughput, which limits the fabrication of large‐area SERS substrates and restricts their practical application in detection analysis. Therefore, a low‐cost, facile, and environmentally friendly fabrication strategy for SERS‐active substrates by sonochemical treatment in conjunction with mechanical stirring without surfactants is proposed for the detection of low concentrations of molecules. Liquid metal alloys were employed as SERS‐active substrate materials and are easily oxidized to form an oxide film in air, resulting in good dispersion of the nanoparticles. In addition, nanograss consisting of rod‐like structures and nanogaps formed on the micro/nanoparticle surface, providing numerous SERS‐active sites. The shape, size, and surface nanostructure of the micro/nanoparticles could be tuned by controlling the ultrasonication time and the stirring speed. The performance of the SERS substrate coated with Au film was evaluated by using rhodamine 6G as a probe. The resulting limit of rhodamine 6G detection for the optimized nanograss‐structured substrate by Raman analysis was as low as 10−7 M, and the standard deviation was 8–15.5%, which meets the requirements for the trace detection of analytes. This facile, large‐scale, low‐cost, and green synthesis of a liquid metal nanograss‐structured substrate with high SERS activity and sensitivity makes it a perfect choice for practical SERS detection applications.
The multi-nozzle electrospinning is under extensive investigations because it is an easy way to enhance the productivity and also feasible to produce special structure fibers such as core-shell fibers and to fabricate composite fibers of those polymers that cannot form blend solution in common solvent. Control over the multi-nozzle electrospinning fibers deposition has attracted increasing attentions. The most common method was to use the auxiliary electrode. However, the concentrated effect of the works of control multi-nozzle electrospinning deposit was inconspicuous. To enhance the controlling of multi-nozzle electrospinning deposition, a set-up based oppositely charged electrospinning was designed. In this set-up the air flow was used to transport neutralized nanofibers. This electrospinning method was named oppositely charged and air auxiliary electrospinning (OCAAES). The capacity of OCAAES in deposition area and pattern controlling were investigated. By the OCAAES, concentrated and several patterned nanofibers deposition were fabricated. Results showed that nanofiber deposition area and pattern of multi-nozzle electrospinning could be controlled actively, and nanofiber deposition could be fabricated in a quick thickening rate.
In this paper, electrospray technology was utilized to fabricate micro membrane. The stable cone-jet injection mode was the key role to atomize uniformity particle and smooth membrane. As applied voltage ranged from 2.5kV to 7.5kV, the stable cone-jet model was built up. When the applied voltage increased from 2.5kV to 7.5kV, the average linear jet length increased from 3.699mm to 4.653mm under the stable cone-jet mode. Under the smaller distance between the nozzle and collector of 3~5cm, electrospray particles with higher solvent content was syncretized into membrane. Larger applied voltage led to higher surface charge density and multiple jets injection mode, in which electrospray particles can be syncretized into membrane structure. The uniformity and compactness of the membranes can be improved through the heat treatment. Smooth and uniform membrane can be fabricated with the heat treatment temperature of 100 . With the help of heat treatment, the thickness of electrospray membrane was decreased from 9.06 μm to 6.41 μm. Electrospray technology provides an excellent way to fabricate polymer micro membrane and had great application potential.
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