Nanosphere lithography for optical fiber tip nanoprobes

This paper reports a simple and economical method for the fabrication of nanopatterned optical fiber nanotips.The proposed patterning approach relies on the use of the nanosphere lithography of the optical fiber end facet.Polystyrene(PS)nanospheres are initially self-assembled in a hexagonal array on the surface of water.The created pattern is then transferred onto an optical fiber tip(OFT).The PS monolayer colloidal crystal on the OFT is the basic building block that is used to obtain different periodic structures by applying further treatment to the fiber,such as metal coating,nanosphere size reduction and sphere removal.Ordered dielectric and metallo-dielectric sphere arrays,metallic nanoisland arrays and hole-patterned metallic films with feature sizes down to the submicron scale are achievable using this approach.Furthermore,the sizes and shapes of these periodic structures can be tailored by altering the fabrication conditions.The results indicate that the proposed self-assembly approach is a valuable route for the development of highly repeatable metallo-dielectric periodic patterns on OFTs with a high degree of order and low fabrication cost.The method can be easily extended to simultaneously produce multiple fibers,opening a new route to the development of fiber-optic nanoprobes.Finally,we demonstrate the effective application of the patterned OFTs as surface-enhanced Raman spectroscopy nanoprobes.

Fabrication of silver nanoparticles decorated anodic aluminum oxide as the SERS substrate for the detection of pesticide thiram

An efficient surface-enhanced Raman scattering(SERS) substrate is developed based on silver nanoparticles decorated anodic aluminum oxide(Ag/AAO).The AAO templates were fabricated using a two-step anodization approach,and silver nanoparticles(Ag NPs) were obtained by thermal decomposition of Ag nitrate in AAO.The structure of Ag/AAO hybrid substrate is characterized by scanning electron microscopy(SEM).The results show that the as-prepared SERS substrates consist of high-density Ag NPs with sizes of tens of nanometers.The Ag NPs are adsorbed on the surface of AAO template in the form of network structure which is called "hot spot".The SERS enhancement ability of the nanostructure is verified using thiram as probing molecules.The limit of detection is as low as 1×10-9 mol/L.The results indicate that the as-prepared substrate possesses excellent SERS sensitivity,high stability and uniformity enhancement.