Zhenyang Wang

Amine-Capped ZnS−Mn2+ Nanocrystals for Fluorescence Detection of Trace TNT Explosive

Mn2+-doped ZnS nanocrystals with an amine-capping layer have been synthesized and used for the fluorescence detection of ultratrace 2,4,6-trinitrotoluene (TNT) by quenching the strong orange Mn2+ photoluminescence. The organic amine-capped nanocrystals can bind TNT species from solution and atmosphere by the acid-base pairing interaction between electron-rich amino ligands and electron-deficient aromatic rings. The resultant TNT anions bound onto the amino monolayer can efficiently quench the Mn2+ photoluminescence through the electron transfer from the conductive band of ZnS to the lowest unoccupied molecular orbital (LUMO) of TNT anions. The amino ligands provide an amplified response to the binding events of nitroaromatic compounds by the 2- to approximately 5-fold increase in quenching constants. Moreover, a large difference in quenching efficiency was observed for different types of nitroaromatic analytes, dependent on the affinity of nitro analytes to the amino monolayer and their electron-accepting abilities. The amine-capped nanocrystals can sensitively detect down to 1 nM TNT in solution or several parts-per-billion of TNT vapor in atmosphere. The ion-doped nanocrystal sensors reported here show a remarkable air/solution stability, high quantum yield, and strong analyte affinity and, therefore, are well-suited for detecting the ultratrace TNT and distinguishing different nitro compounds.

Resonance Energy Transfer-Amplifying Fluorescence Quenching at the Surface of Silica Nanoparticles toward Ultrasensitive Detection of TNT

This paper reports a resonance energy transfer-amplifying fluorescence quenching at the surface of silica nanoparticles for the ultrasensitive detection of 2,4,6-trinitrotoluene (TNT) in solution and vapor environments. Fluorescence dye and organic amine were covalently modified onto the surface of silica nanoparticles to form a hybrid monolayer of dye fluorophores and amine ligands. The fluorescent silica particles can specifically bind TNT species by the charge-transfer complexing interaction between electron-rich amine ligands and electron-deficient aromatic rings. The resultant TNT-amine complexes bound at the silica surface can strongly suppress the fluorescence emission of the chosen dye by the fluorescence resonance energy transfer (FRET) from dye donor to the irradiative TNT-amine acceptor through intermolecular polar-polar interactions at spatial proximity. The quenching efficiency of the hybrid nanoparticles with TNT is greatly amplified by at least 10-fold that of the corresponding pure dye. The nanoparticle-assembled arrays on silicon wafer can sensitively detect down to approximately 1 nM TNT with the use of only 10 microL of solution (approximately 2 pg TNT) and several ppb of TNT vapor in air. The simple FRET-based nanoparticle sensors reported here exhibit a high and stable fluorescence brightness, strong analyte affinity, and good assembly flexibility and can thus find many applications in the detection of ultratrace analytes.

Design of Sb2S3 nanorod-bundles: imperfect oriented attachment

The large scale formation of uniform Sb2S3 nanorod-bundles has been achieved via a simple and mild hydrothermal approach with the assistance of polyvinylpyrrolidone. By closely inspecting the growth process and the crystallographic analysis of as-synthesized products, conclusive evidence has been provided to show that the growth mechanism of such nanorod-bundles is imperfect oriented attachment. The anisotropic adsorption of polyvinylpyrrolidone at the different surfaces of Sb2S3 nanocrystals assists the one-dimensional preferential growth; it is just the misorientations that result in the nanorod-based superstructures. Moreover, the hydrothermal treatment time plays a crucial role, and can be used as the parameter to control the size and morphology of the bundles. This simple approach promises future large-scale controlled synthesis of various nanobody-based superstructures for many important applications in nanotechnology.

Inverted Opal Fluorescent Film Chemosensor for the Detection of Explosive Nitroaromatic Vapors through Fluorescence Resonance Energy Transfer

This paper reports an inverted opal fluorescence chemosensor for the ultrasensitive detection of explosive nitroaromatic vapors through resonance-energy-transfer-amplified fluorescence quenching. The inverted opal silica film with amino ligands was first fabricated by the acid-base interaction between 3-aminopropyltriethoxysilane and surface sulfonic groups on polystyrene microsphere templates. The fluorescent dye was then chemically anchored onto the interconnected porous surface to form a hybrid monolayer of amino ligands and dye molecules. The amino ligands can efficiently capture vapor molecules of nitroaromatics such as 2,4,6-trinitrotoluene (TNT) through the charge-transfer complexing interaction between electron-rich amino ligands and electron-deficient aromatic rings. Meanwhile, the resultant TNT-amine complexes can strongly suppress the fluorescence emission of the chosen dye by the fluorescent resonance energy transfer (FRET) from the dye donor to the irradiative TNT-amino acceptor through intermolecular polar-polar resonance at spatial proximity. The quenching response of the highly ordered porous films with TNT is greatly amplified by at least 10-fold that of the amorphous silica films, due to the interconnected porous structure and large surface-to-volume ratio. The inverted opal film with a stable fluorescence brightness and strong analyte affinity has lead to an ultrasensitive detection of several ppb of TNT vapor in air.

Copolypeptide-doped polyaniline nanofibers for electrochemical detection of ultratrace trinitrotoluene.

This paper demonstrates a new electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene (TNT) with synthetic copolypeptide-doped polyaniline nanofibers. The copolypeptide, comprising of glutamic acid (Glu) and lysine (Lys) units, is in situ doped into polyaniline through the protonation of the imine nitrogen atoms of polyaniline by the free carboxylic groups of Glu segments, resulting in the formation of polyaniline nanofibers of emeraldine salt. The free amino groups of Lys segments at the surface of nanofibers provide the receptor sites of TNT through the formation of charge-transfer complex between the electron-rich amino groups and the electron-deficient aromatic rings. Adsorptive stripping voltammetry results demonstrate that the poly(Glu-Lys)-doped nanofibers confined onto glassy carbon electrodes exhibit a remarkable enriching effect and thus sensitive electrochemical response to TNT with a linear dynamic range of 0.5-10 microM and a detection limit down to 100 nM. Moreover, other kinds of nitro compounds show different redox behaviors from TNT at the doped nanofibers, and thus do not interfere with the electrochemical detection of TNT. This study essentially offers a new and simple method for electrochemical detection of ultratrace TNT.

Controlled heat release of new thermal storage materials: the case of polyethylene glycol intercalated into graphene oxide paper

Brick-and-mortar microstructures of graphene oxide–polyethylene glycol (PEG) composite papers were easily prepared with large area. The freezing point of the PEG intercalated into the shaped composite paper could be successively decreased down to room temperature, while the melting point was kept constant with that of bulk PEG, which means controlled heat release was thus achieved.

Diverting phase transition of high-melting-point stearic acid to room temperature by microencapsulation in boehmite

Organic phase change materials (OPCMs) have long been recognized as potentially reversible thermal energy storage candidates due to their ability to reversibly store or release large amounts of latent heat when changing from one physical state to another. For application of which in solar heat storage, reducing their relatively high phase transition temperature (TC) to room temperature is still challenging. Herein, a microemulsion with metastable interface is adopted for in situ synthesis of sphere-like structure stearic acid (SA)@boehmite (γ-AlOOH) microcapsules. Interestingly, when the high-melting-point SA crystals (TC = 70.8 °C) were capsulated into boehmite nanoshells, their phase transition could be diverted to room temperature (∼21 °C), which means about 50 °C decrease of their phase change temperature has been achieved. This dramatic change could be due to a confinement effect on the interface between SA cores and the boehmite nanoshells, which leads to a change of geometric factors and enhancement of shell-SA interactions. Furthermore, the heat energy storage density (∼140 kJ kg−1) of the obtained SA@γ-AlOOH microcapsules is higher than that of most common room temperature PCMs, suggesting an efficient heat storage ability. This kind of shape-stabilized microcapsule can be considered as candidate room temperature PCMs for thermal energy storage.

Ultrathin Cu7S4 nanosheets-constructed hierarchical hollow cubic cages: one-step synthesis based on Kirkendall effect and catalysis property

Ultrathin two-dimensional (2D) nanosheets are a conceptually new category of nanoscale materials. Integration/assembly of individual 2D nanosheets into 3D hierarchical structures is an enormous challenge and an essential requirement for their application. Here we first report the direct synthesis of Cu7S4 hierarchical hollow cubic cages assembled by ultrathin nanosheets based on the Kirkendall effect. Slowly released Cu+ from Cu2O cubic template-crystals and S2− from decomposed thioacetamide (TAA) can react with each other and form a diffusion pair, which provides a thermodynamic and kinetic equilibrium to be responsible for the formation of ultrathin Cu7S4 nanosheets and the Cu7S4 hierarchical hollow cubic cages. Using this unique hollow structure and the outstanding catalytic property of the Cu7S4 nanosheets, as an example, we successfully demonstrate that Cu7S4 nanocages can effectively catalyse the “clock reaction”, which is a periodic cycle redox oscillation reaction between methylene blue (MB) and colorless leucomethylene blue (LMB). The unique hierarchical structure has been found to enhance the rate of this redox reaction via the ultrathin nanocatalyst. This work develops a facile strategy for synthesizing 3D hierarchical structures constructed by ultrathin nanosheets and demonstrates their superior ability to optimize the nanosheet-catalyzed clock reaction.

Well-dispersed magnetic iron oxide nanocrystals on sepiolite nanofibers for arsenic removal

A novel nanostructure composed of magnetic iron oxide nanocrystals (MI) anchored on a sepiolite nanofiber backbone with excellent arsenic adsorption performance has been successfully developed. Sepiolites (SEPs) as typical nano-geomaterials with low cost, large specific surface (ca. 300 m2 g−1) and tunable surface chemistry are chosen as the host matrix. Transmission electron microscopy confirms that uniform Fe2O3 nanocrystals with an average particle size of ∼9 nm are spatially well-dispersed and anchored on the sepiolite backbone at a high Fe2O3 content of 33.2 wt%, rather than forming aggregates on the external surface. MI/SEPs have a high specific surface area, high loading amount, the non-aggregated nature of Fe2O3 nanocrystals, good dispersion and magnetic properties, making them promising for use as a separable adsorbent for As(III) removal with high adsorption capacity and magnetic separation properties. The maximum adsorption capacity has a wonderful value of 50.35 mg g−1 for As(III) on the MI/SEPs, which is higher than those of previously reported adsorbents. Moreover, MI/SEPs can reduce the concentration of As(III) from 140 to 1.5 μg L−1. MI/SEPs also show high removal ratios of 96.4% without any pre-treatment in real groundwater with an arsenic concentration of 456.5 μg L−1.

Janus particle arrays with multiple structural controlling abilities synthesized by seed-directed deposition

Janus particle arrays have attracted much investigation interest in recent years due to their wide application potentialities. Here, we introduce a new protocol to synthesize Janus particle arrays depending on seed-directed eletrophoretic deposition on monolayer colloidal crystal (MCC) templates. The size and feature of the Janus particles can be conveniently tailored by selecting different sized polystyrene spheres and deposition current densities and/or times, respectively. Non-close-packed Janus particle arrays can be prepared by adopting plasma treated monolayer colloidal crystal templates. The spacing between neighbouring Janus particles in the ordered array is determined by the plasma etching time of the MCC template. Due to the symmetry breaking and the plasmon hybridization, the Janus particle arrays show interesting plasmonic properties. They have multiple plasmonic peaks and have infrared absorption, making them have applications in sensing and bio-related areas.