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The first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described. The utilized polymerization technique, namely atom transfer radical precipitation polymerization (ATRPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding kinetics and an appreciable selectivity over structurally related compounds. The living chain propagation mechanism in ATRPP results in MIP spherical particles with diameters (number‐average diameter Dn ≈ 3 μm) much larger than those prepared via traditional radical precipitation polymerization (TRPP). In addition, the MIP microspheres prepared via ATRPP have also proven to show significantly higher high‐affinity binding site densities on their surfaces than the MIP generated via TRPP, while the binding association constants Ka and apparent maximum numbers Nmax of the high‐affinity sites as well as the specific template bindings are almost the same in the two cases. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3257–3270, 2009

Uniform CdS/ZnO core/shell nanowires are hydrothermally synthesized using a two‐step process and assembled into a photodetector and a NO2 optoelectronic sensor for the first time. The corresponding photodetector exhibits a fast, reversible, and stable optoelectronic response with a rise time of ∼26 ms, a decay time of ∼2.1 ms and a stability of over 5 months. The remarkable photosensitivity and fast photoresponse are attributed to the formation of a heterojunction structure between CdS and ZnO, which greatly inhibits the recombination of photoinduced electrons and holes. The CdS/ZnO core/shell nanowires also show an excellent visible‐light‐activated gas sensing performance towards ppb‐level NO2 at room temperature. The responses range from 6.7% to 337% toward NO2 concentrations of 5 to 1000 ppb. It is found that the sensitivity of the NO2 sensor is dependent on the illuminated light intensity with a maximum value at 0.68 mW/cm2. The sensing mechanisms of the CdS/ZnO nanowires under visible‐light irradiation and the influence of light intensity are also discussed. The present CdS/ZnO core/shell nanowire not only benefits the fabrication of efficient photodetectors, but also makes the instant, optically controlled sensing of ppb‐level NO2 gas possible.

The development of portable, real-time, and cheap platforms to monitor ultratrace levels of explosives is of great urgence and importance due to the threat of terrorism attacks and the need for homeland security. However, most of the previous chemiresistor sensors for explosive detection are suffering from limited responses and long response time. Here, a transition-metal-doping method is presented to remarkably promote the quantity of the surface defect states and to significantly reduce the charge transfer distance by creating a local charge reservoir layer. Thus, the sensor response is greatly enhanced and the response time is remarkably shortened. The resulting sensory array can not only detect military explosives, such as, TNT, DNT, PNT, PA, and RDX with high response, but also can fully distinguish some of the improvised explosive vapors, such as AN and urea, due to the huge response reaching to 100%. Furthermore, this sensory array can discriminate ppb-level TNT and ppt-level RDX from structurally similar and high-concentration interfering aromatic gases in less than 12 s. Through comparison with the previously reported chemiresistor or Schottky sensors for explosive detection, the present transition-metal-doping method resulting ZnO sensor stands out and undoubtedly challenges the best.

4039wileyonlinelibrary.com mole cules and depends highly on the analyte concentrations. [8][9][10][11][12] As a result, the traditional Ohm-contacted nanosensor has diffi culty in realizing the ultrasensitive detection in real circumstances where open environment must be considered. Recently, it was demonstrated that Schottky contact could largely improve the sensitivity of nanosensors due to that Schottky barrier serves as a "gate" controlling the current passing through the barrier, [ 13,14 ] and the value of this current highly depends on the Schottky barrier height (SBH). A small change in SBH will lead to a huge change in current, which is the basis of the Schottky barrier enhanced sensing. [ 13 ] The selection of the components of the Schottky junction is of vital importance to improve the sensor performance, which highly depends on the energy band structure and adsorption characteristics. It is reported that a higher SBH favors a better sensitivity in a Schottky-gated sensor toward electron acceptor analytes detection, while for electron donor analytes detection, the result is opposite. [ 15 ] Thus, the insertion of another semiconductor that could both modulate the SBH and increase the adsorption energy will greatly increase the sensitivity and selectivity in a Schottky junction sensor. Graphene or reduced graphene oxide (rGO) with high charge carrier mobility, atomically thin nature and abundant adsorption sites, [16][17][18][19][20] makes the semiconductor/graphene Schottky heterojunction (Barristor) ultrasensitive for gas sensing. [ 21,22 ] Vertical silicon nanowires (SiNWs) array offers distinct merits in terms of the capability for surface functionalization and the suffi cient gaps for molecules diffusion, and SiNWs array-based sensor has been considered an ideal platform for gas sensing due to the higher signal-to-noise ratios and faster response. [ 23,24 ] The electron affi nity of TiO 2 (4.0 eV) is only a bit smaller than that of silicon (4.05 eV); [ 25 ] thus the insertion of TiO 2 into Si/rGO should be an ideal choice to support the above assertion. As a result, the SiNWs array/TiO 2 /rGO ternary junction will provide a new approach for designing ultrasensitive and selective sensors.Nitro-explosives is one of the most important categories in common explosives, and the detection of them has been a research focus due to plenty of adverse events, increasing threat of terrorism attack, and the need for homeland security. [ 1,9,26,27 ] The sensitive, selective, and rapid detection of nitro-explosives vapors is still a challenge due to the low vapor pressure of

For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (∼10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective π-π interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives.

This article describes for the first time the development of a new polymerization technique by introducing iniferter‐induced “living” radical polymerization mechanism into precipitation polymerization and its application in the molecular imprinting field. The resulting iniferter‐induced “living” radical precipitation polymerization (ILRPP) has proven to be an effective approach for generating not only narrow disperse poly(ethylene glycol dimethacrylate) microspheres but also molecularly imprinted polymer (MIP) microspheres with obvious molecular imprinting effects towards the template (a herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D)), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant Ka and apparent maximum number Nmax for the high‐affinity sites of the 2,4‐D imprinted polymer were determined by Scatchard analysis and found to be 1.18 × 104 M−1 and 4.37 μmol/g, respectively. In addition, the general applicability of ILRPP in molecular imprinting was also confirmed by the successful preparation of MIP microspheres with another template (2‐chloromandelic acid). In particular, the living nature of ILRPP makes it highly useful for the facile one‐pot synthesis of functional polymer/MIP microspheres with surface‐bound iniferter groups, which allows their direct controlled surface modification via surface‐initiated iniferter polymerization and is thus of great potential in preparing advanced polymer/MIP materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3217–3228, 2010

In order to sensitively, selectively, and rapidly detect the constituents relevant to improvised explosive devices (IEDs), the sensing properties of ZnS nanocrystals (NCs) are regulated by tailoring the doping level of Mn2+. The responses of the sensors fabricated by ZnS NCs with different Mn‐doping levels (Mn:ZnS) toward the constituents, such as sulphur powder and black powder, generally increases first and then decreases with the increase of the concentration of doped Mn2+, and reaches the climate with an atomic ratio of 2.23% at room temperature. The sensory array based on eight sensors of Mn:ZnS NCs can realize the detection of two typical military explosives and six constituents relevant to IEDs within 7 s and can recover in 19 s. Furthermore, the fingerprinting of the constituents is achieved by pattern recognizing the inherent kinetics and thermodynamics of interaction between the sensory array and the constituents. Thus, a simple chemiresistive sensing strategy based on semiconductor NCs which can rapidly, supersensitively, and discriminatively detect the constituents relevant to IEDs is explored for the first time.