Sea urchin-like CuO particles prepared using Cu3(PO4)2 flowers as precursor for high-performance ethanol sensing.

Cu3(PO4)2 flowers are reported for the first time as a solid precursor for the preparation of hierarchical CuO particles with sea urchin-like morphology in the absence of self-assembled templates or matrixes. In the alkaline condition, Cu3(PO4)2 transforms into Cu(OH)2 firstly, and then into CuO through dehydration at room temperature. Different from soluble Cu salt as precursor, the basic building blocks for CuO are continuously supplied in a controlled manner form Cu3(PO4)2 precursor, which ensures a nearly sustained supersaturated concentration that favors heterogeneous nucleation and progressive growth of sea urchin-like CuO particles. The gas sensing property of as-prepared sea urchin-like CuO particles to ethanol is investigated. The sea urchin-like CuO particles exhibit a good sensing performance in terms of high response, short response/recovery time, good selectivity, good reproducibility, and long-term stability. The facile strategy demonstrated here opens up a new strategy to fabricate hierarchical CuO particles with enormous potential from the perspective of practical application.

Dynamic Tunable Color Display Based on Metal-Insulator-Metal Resonator with Polymer Brush Insulator Layer as Signal Transducer.

Dynamic color-changing nanomaterials have been widely investigated for applications in fields like optical sensors, wearable activity monitors, smart electronic devices, and anticounterfeiting materials due to the excellent ability to change their optical properties with external variation. Here, a simple metal-insulator-metal (MIM) trilayer Fabry-Perot resonance cavity with a poly(N-isopropylacrylamide) (PNIPAm) brush layer as a responsive element is reported as a thermal-induced colorimetric response platform. The dynamic changes of conformation and physical properties of PNIPAm brush layer in response to external signals give rise to a significant color change of the MIM Fabry-Perot resonance cavity. This MIM Fabry-Perot resonance cavity shows the advantages of dynamic color change, rapid response, good repeatability, and simple construction. Additionally, the as-prepared MIM cavity shows great potential in various applications such as color printing, multicolor indicator, and information anticounterfeiting.

Fabrication of Metal-Organic Framework and Infinite Coordination Polymer Nanosheets by the Spray Technique.

We have developed a rapid and convenient method for fabricating metal-organic framework (MOF) and infinite coordination polymer (ICP) nanosheets by spraying the atomized solution of metal ions onto the organic ligand solution. Nanosheet formation could be attributed to the anisotropic diffusion of metal ions in the ligand solution, which may give rise to a lateral interface of metal ions and organic ligands, where the crystals tend to grow laterally in the form of nanosheets. Three kinds of Zn- and Cu-based MOF nanosheets and two kinds of Co-based ICP nanosheets have been successfully obtained by spraying under mild conditions. The two-dimensional structures of nanosheets with a nanometer thickness and a homogeneous size can be evidenced by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopy measurements. Furthermore, the fabricated ICP nanosheets have exhibited efficient catalytic performance for the conversion of CO2 to high-value-added chemicals. This spray technique simplifies the nanosheet production process by industrialized means and enhances its controllability by the fast liquid-liquid interfacial fabrication, thus allowing access to the industrialized fabrication of MOF and ICP nanosheets.

Responsive etalon based on PNIPAM@SiO2 composite spacer with rapid response rate and excellent repeatability for sensing application.

In this paper, we demonstrate a responsive etalon fabricated through combining colloidal lithography and surface-initiated atom-transfer radical polymerization (SI-ATRP). The responsive etalon is simply constructed with one responsive spacer sandwiched by two reflective layers, and the middle responsive spacer is constructed by grafting thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes on a SiO2 nanosphere array. The etalon possesses one single interference peak in the visible region, and the interference peak changes sensitively against the concentration of the external stimulant (water vapor) or the temperature of the system, owing to the responsiveness of the PNIPAM brush. Importantly, the as-prepared etalon shows a rapid response rate and excellent stability, and it is also handy to realize the miniaturization and integration of the responsive etalon based on a conventional micro-fabrication method. These features all make the as-prepared responsive etalon an attractive candidate for future sensing applications. We believe such responsive etalons are promising for the fabrication of smart photonic materials and optical sensors that may be useful in tissue engineering, medical diagnosis, public security, and biochip areas.

Thermal annealing: a facile way of conferring responsivity to inert alkyl-chain-passivated nanoparticle arrays.

This work demonstrates a facile post-treatment strategy, vacuum thermal annealing, to fabricate a dodecanethiol-passivated gold nanoparticle (Au NP) array with organic solvent sensitivity. Through investigating the structure change of the Au NP array, it was found that the interparticle distance decreased during vacuum heat treatment, which meant a closer arrangement of the particles and a more dense packing of the dodecanethiol ligands in the interparticle region. The condensation would increase the interaction of the alkyl chain and enhance their interdigitation. Furthermore, on the basis of the stretching of the alkyl chains in organic solvents, the thermally treated Au NP array showed a good response to organic solvent or vapor by using the interdigitated dodecanethiol network as its responsive unit. The alkyl chains stretch to different extents in different organic solvents, leading to differences in interparticle distance, which provided a distinct blue shift of maximum wavelength upon exposure to various organic solvents or vapors. All of these results indicated that thermal annealing was an efficient way to confer responsivity to inert Au NP arrays. Together with the cost-effectiveness of such NP arrays, this study has potential in the development of economical sensors for medical diagnostics, food safety screening, and environmental pollution monitoring.