Qitao Zhou

Ag-nanoparticles-decorated NiO-nanoflakes grafted Ni-nanorod arrays stuck out of porous AAO as effective SERS substrates

NiO-nanoflakes (NiO-NFs) grafted Ni-nanorod (Ni-NR) arrays stuck out of the porous anodic aluminum oxide (AAO) template are achieved by a combinatorial process of AAO-confined electrodeposition of Ni-NRs, selectively etching part of the AAO template to expose the Ni-NRs, wet-etching the exposed Ni-NRs in ammonia to obtain Ni(OH)2-NFs grafted onto the cone-shaped Ni-NRs, and annealing to transform Ni(OH)2-NFs in situ into NiO-NFs. By top-view sputtering, Ag-nanoparticles (Ag-NPs) are decorated on each NiO-NFs grafted Ni-NR (denoted as NiO-NFs@Ni-NR). The resultant Ag-NPs-decorated NiO-NFs@Ni-NR (denoted as Ag-NPs@NiO-NFs@Ni-NR) arrays exhibit not only strong surface-enhanced Raman scattering (SERS) activity but also reproducible SERS-signals over the whole array. It is demonstrated that the strong SERS-activity is mainly ascribed to the high density of sub-10 nm gaps (hot spots) between the neighboring Ag-NPs, the semiconducting NiO-NFs induced chemical enhancement effect, and the lightning rod effect of the cone-shaped Ni-NRs. The three-level hierarchical nanostructure arrays stuck out of the AAO template can be utilized to probe polychlorinated biphenyls (PCBs, a kind of global environmental hazard) with a concentration as low as 5 × 10(-6) M, showing promising potential in SERS-based rapid detection of organic environmental pollutants.

A Surface-Enhanced Raman Scattering Sensor Integrated with Battery-Controlled Fluidic Device for Capture and Detection of Trace Small Molecules

For surface-enhanced Raman scattering (SERS) sensors, one of the important issues is the development of substrates not only with high SERS-activity but also with strong ability to capture analytes. However, it is difficult to achieve the two goals simultaneously especially when detecting small molecules. Herein a compact battery-controlled nanostructure-assembled SERS system has been demonstrated for capture and detection of trace small molecule pollutants in water. In this SERS fluidic system, an electrical heating constantan wire covered with the vertically aligned ZnO nanotapers decorated with Ag-nanoparticles is inserted into a glass capillary. A mixture of thermo-responsive microgels, Au-nanorods colloids and analyte solution is then filled into the remnant space of the capillary. When the system is heated by switching on the battery, the thermo-responsive microgels shrink, which immobilizes the analyte and drives the Au-nanorod close to each other and close to the Ag-ZnO nanotapers. This process has also created high-density “hot spots” due to multi-type plasmonic couplings in three-dimensional space, amplifying the SERS signal. This integrated device has been successfully used to measure methyl parathion in lake water, showing a great potential in detection of aquatic pollutants.

Nanochannel-Assisted Perovskite Nanowires: From Growth Mechanisms to Photodetector Applications

Growing interest in hybrid organic-inorganic lead halide perovskites has led to the development of various perovskite nanowires (NWs), which have potential use in a wide range of applications, including lasers, photodetectors, and light-emitting diodes (LEDs). However, existing nanofabrication approaches lack the ability to control the number, location, orientation, and properties of perovskite NWs. Their growth mechanism also remains elusive. Here, we demonstrate a micro/nanofluidic fabrication technique (MNFFT) enabling both precise control and in situ monitoring of the growth of perovskite NWs. The initial nucleation point and subsequent growth path of a methylammonium lead iodide-dimethylformamide (MAPbI3·DMF) NW array can be guided by a nanochannel. In situ UV-vis absorption spectra are measured in real time, permitting the study of the growth mechanism of the DMF-mediated crystallization of MAPbI3. As an example of an application of the MNFFT, we demonstrate a highly sensitive MAPbI3-NW-based photodetector on both solid and flexible substrates, showing the potential of the MNFFT for low-cost, large-scale, highly efficient, and flexible optoelectronic applications.

Permanent encapsulation of nanoparticle patterns formed by inkjet printer for transparent and flexible anti-counterfeit applications

The self-assembly and deposition mechanisms of nanoparticles in droplets on a substrate are significant in many inkjet printing-based industrial applications such as microelectronics, display systems, and paint manufacturing. In this study, we describe the underlying lack mechanisms of the self-assembly and deposition behavior of nanoparticles in inkjet-printed. We also demonstrate the development of flexible and photonic crystals structural color based on self-assembled silica photonic crystals.

Inkjet-printed AG micro-/nanostructure clusters on CU substrates for in-situ pre-concentration and surface-enhanced Raman scattering

Here, we describe a novel method for SERS substrates using inkjet printing that allows AgNO3 solution to be regularly injected onto a superhydrophobically functionalized Cu substrate. The chemical replacement reaction occurs only within droplet-injected areas, creating a hydrophilic Ag micro-/nanostructures and a wettability gradient on the Cu surface. As a sample drop containing analytes and Au nanoparticles (Au-NPs) evaporates on the Cu substrate, the analytes and Au-NPs are delivered to the hydrophilic Ag nanoplate array (Ag-NPA), facilitating simple, easy, and in-situ pre-concentration and sensitive SERS detection. Our approach made it possible to successfully detect antibiotics at very low concentrations, thereby demonstrating a remarkable potential of the inkjet printing method for SERS substrates.