Gong Wang

Fabrication of photopolymer hierarchical micronanostructures by coupling electrospinning and photolithography for SERS substrates

AbstractReported here is the fabrication of photopolymer hierarchical micronanostructures through a combinative process of electrospinning and subsequent photolithography. Electrospun SU-8 (epoxy-based negative photoresist) nanofiber films have been patterned into gratings with periods of 100, 200, 300, and 400 μm, respectively. Deposition of a silver nanolayer on these interlaced nanofiber films would lead to the formation of various plasmonic nanostructures, and therefore, giving rise to abundant surface-enhanced Raman scattering (SERS) “hot spots”. In the detection of Rhodamine 6G (R6G), probing molecule, the resultant SERS substrates show both high sensitivity and good reproducibility. The SERS enhancement factor could reach as high as ∼108, indicating high efficiency. The fabrication of patterned, highly efficient SERS substrates may hold a great promise for the integration of SERS substrates in various microdevices such as microfluidic chips.

Preparation of a Fe3O4–Au–GO nanocomposite for simultaneous treatment of oil/water separation and dye decomposition

A nanocomposite capable of simultaneously controlling multiple water pollutants (soluble organic dye and insoluble chemical solvent) has been obtained. The Au and Fe3O4 nanoparticles (NPs) were modified on a graphene oxide (GO) surface via light reduction and covalent attachment. The obtained Fe3O4-Au-GO nanocomposite has magnetic driving ability and catalytic applications. The nanocomposite can form emulsions after wrapping an insoluble and volatile organic solvent inside; moreover, the multi-layer graphene shell structure may delay volatilization of the solvent, ensuring that the oil droplets are collected efficiently and completely by the Fe3O4-Au-GO nanocomposite. At the same time, the Au NPs on the surface of the composite can effectively catalyze the decomposition of an organic dye in water and the recovery of the nanocomposite catalyst can also be realized using an external magnetic field. The simultaneous treatment of non-soluble oil (organic solvents) and organic dyes in water can be realized by the Fe3O4-Au-GO nanocomposite. Therefore, based on surface modification of GO, one material with two types of water pollution treatment functions was realized. This provides a new way for the simultaneous treatment of oil separation and dye decomposition, and the assembled structure may result in emulsions to give new applications in fuel cells and other fields.

Fabrication and Manipulation of Magnetic Composite Particles with Specific Shape and Size

The fabrication of microscale polyethylene glycol diacrylate(PEGDA) hydrogel particles was demonstrated via magnetic property ultraviolet(UV) lithography techniques, polydimethylsiloxane(PDMS) soft stamp preparation techniques and micro-nano imprint technology in this paper. The results of compositional and morphological characterizations of magnetic microparticles show that the Fe3O4 nanoparticles with an average diameter of 100 nm are uniformly dispersed in hydrogel. Owing to the excellent magnetism of Fe3O4 nanoparticles, the fabricated hydrogel microparticles with different sizes and shapes were manipulated in water via applying an external magnetic fields. Three types of motions, translation, rotation and flip, were demonstrated with the manipulator. These microscale magnetic PEGDA hydrogel particles have a great application potential in manufacturing process, micro/nanomotors, and machines.

Ferrofluids Containing Fe 3 O 4 Nanoparticles in Solidified Photoresist Carrier

Ferrofluids, formed by magnetic nanoparticles uniformly dispersed in a liquid carrier, respond to an external magnetic field, which enable the fluid’s position by applying a magnetic field. Here, ferrofluids composed of Fe3O4 nanoparticles with oleic acid and oleylamine as the surfactant and photoresist, respectively, were prepared. Under an external magnetic field, the movement and the position of ferrofluids and the injection of the fluids into complex shapes were easily achieved. The ferrofluid surfaces were distorted under the magnetic field, and the surface structue was controlled by the applied field strength. Using a photoresist as the liquid carrier, it was possible to solidify the ferrofluids by UV irradiation. The shape and the position of the solid superparamagnetic nanoparticles/polymer composites were also determined by the external magnetic field.