Zhenyi Zhang

Multichannel‐Improved Charge‐Carrier Dynamics in Well‐Designed Hetero‐nanostructural Plasmonic Photocatalysts toward Highly Efficient Solar‐to‐Fuels Conversion

The charge-carrier dynamics process in well-designed hetero-nanostructural plasmonic photocatalysts is greatly improved through a multichannel sensitization effect, which therefore results in a significant enhancement of the efficiencies of solar-to-fuels conversion.

Hierarchical Sheet-on-Sheet ZnIn2S4/g-C3N4 Heterostructure with Highly Efficient Photocatalytic H2 production Based on Photoinduced Interfacial Charge Transfer.

We have realized in-situ growth of ultrathin ZnIn2S4 nanosheets on the sheet-like g-C3N4 surfaces to construct a “sheet-on-sheet” hierarchical heterostructure. The as-synthesized ZnIn2S4/g-C3N4 heterojunction nanosheets exhibit remarkably enhancement on the photocatalytic activity for H2 production. This enhanced photoactivity is mainly attributed to the efficient interfacial transfer of photoinduced electrons and holes from g-C3N4 to ZnIn2S4 nanosheets, resulting in the decreased charge recombination on g-C3N4 nanosheets and the increased amount of photoinduced charge carriers in ZnIn2S4 nanosheets. Meanwhile, the increased surface-active-sites and extended light absorption of g-C3N4 nanosheets after the decoration of ZnIn2S4 nanosheets may also play a certain role for the enhancement of photocatalytic activity. Further investigations by the surface photovoltage spectroscopy and transient photoluminescence spectroscopy demonstrate that ZnIn2S4/g-C3N4 heterojunction nanosheets considerable boost the charge transfer efficiency, therefore improve the probability of photoinduced charge carriers to reach the photocatalysts surfaces for highly efficient H2 production.

A flexible and superhydrophobic upconversion-luminescence membrane as an ultrasensitive fluorescence sensor for single droplet detection

A Ln3+-doped (Yb3+, Tm3+ or Yb3+, Er3+ co-doped) NaYF4 nanoparticle/polystyrene hybrid fibrous membrane (HFM) was fabricated using an electrospinning technique. The HFM shows upconversion luminescence (UCL), flexibility, superhydrophobicity and processability. The UCL membrane can be used as a fluorescence sensor to detect bioinformation from a single water droplet (~10 μl). Based on the fluorescence resonance energy transfer, the detection limits of this sensor can reach 1 and 10 ppb for the biomolecule, avidin, and the dye molecule, Rhodamine B, respectively, which are superior to most of the fluorescence sensors reported in previous works. After the fluorescence detection, the target droplet was easily removed without residues on the UCL membrane surface due to its superhydrophobic property, which exhibits an excellent recyclability that cannot be achieved by traditional liquid-based detection systems.

Controllable assembly of SnO2 nanocubes onto TiO2 electrospun nanofibers toward humidity sensing applications

One-dimensional SnO2/TiO2 heterostructures were successfully synthesized through the hydrothermal assembly of the single-crystalline SnO2 nanocubes onto the TiO2 electrospun nanofibers. The as-synthesized heterostructures with controllable coverage density of SnO2 nanocubes were then coated onto the ceramic-based interdigital electrodes to produce the humidity nanosensors for the investigation of their humidity sensing characteristics. The results showed that the optimal nanosensor with ∼20 at% SnO2-based heterostructure exhibited good humidity sensitivity, fast response–recovery behavior, low humidity hysteresis, and good reproducibility. In particular, the response and recovery times of this optimal nanosensor could reach ∼2.4 s and ∼30.2 s, respectively, which were considerably shorter than the corresponding values of TiO2 nanofiber-based humidity nanosensors. The improved sensitivity characteristics for the SnO2/TiO2 heterostructures can be attributed to the interfacial electron transfer between SnO2 nanocubes and TiO2 nanofibers, which leads to an appropriate height of the potential barrier on the surface of the heterostructures for water adsorption and desorption. Our proposed humidity sensing mechanism would provide opportunities to guide the design and fabrication of other high-performance humidity sensors based on semiconductor heterostructures.

IR‐Driven Ultrafast Transfer of Plasmonic Hot Electrons in Nonmetallic Branched Heterostructures for Enhanced H2 Generation

The ultrafast transfer of plasmon-induced hot electrons is considered an effective kinetics process to enhance the photoconversion efficiencies of semiconductors through strong localized surface plasmon resonance (LSPR) of plasmonic nanostructures. Although this classical sensitization approach is widely used in noble-metal-semiconductor systems, it remains unclear in nonmetallic plasmonic heterostructures. Here, by combining ultrafast transient absorption spectroscopy with theoretical simulations, IR-driven transfer of plasmon-induced hot electron in a nonmetallic branched heterostructure is demonstrated, which is fabricated through solvothermal growth of plasmonic W18 O49 nanowires (as branches) onto TiO2 electrospun nanofibers (as backbones). The ultrafast transfer of hot electron from the W18 O49 branches to the TiO2 backbones occurs within a timeframe on the order of 200 fs with very large rate constants ranging from 3.8 × 1012 to 5.5 × 1012 s-1 . Upon LSPR excitation by low-energy IR photons, the W18 O49 /TiO2 branched heterostructure exhibits obviously enhanced catalytic H2 generation from ammonia borane compared with that of W18 O49 nanowires. Further investigations by finely controlling experimental conditions unambiguously confirm that this plasmon-enhanced catalytic activity arises from the transfer of hot electron rather than from the photothermal effect.

Near-Infrared-Plasmonic Energy Upconversion in a Nonmetallic Heterostructure for Efficient H2 Evolution from Ammonia Borane

Abstract Plasmonic metal nanostructures have been widely used to enhance the upconversion efficiency of the near‐infrared (NIR) photons into the visible region via the localized surface plasmon resonance (LSPR) effect. However, the direct utilization of low‐cost nonmetallic semiconductors to both concentrate and transfer the NIR‐plasmonic energy in the upconversion system remains a significant challenge. Here, a fascinating process of NIR‐plasmonic energy upconversion in Yb3+/Er3+‐doped NaYF4 nanoparticles (NaYF4:Yb‐Er NPs)/W18O49 nanowires (NWs) heterostructures, which can selectively enhance the upconversion luminescence by two orders of magnitude, is demonstrated. Combined with theoretical calculations, it is proposed that the NIR‐excited LSPR of W18O49 NWs is the primary reason for the enhanced upconversion luminescence of NaYF4:Yb‐Er NPs. Meanwhile, this plasmon‐enhanced upconversion luminescence can be partly absorbed by the W18O49 NWs to re‐excite its higher energy LSPR, thus leading to the selective enhancement of upconversion luminescence for the NaYF4:Yb‐Er/W18O49 heterostructures. More importantly, based on this process of plasmonic energy transfer, an NIR‐driven catalyst of NaYF4:Yb‐Er NPs@W18O49 NWs quasi‐core/shell heterostructure, which exhibits a ≈35‐fold increase in the catalytic H2 evolution from ammonia borane (BH3NH3) is designed and synthesized. This work provides insight on the development of nonmetallic plasmon‐sensitized optical materials that can potentially be applied in photocatalysis, optoelectronic, and photovoltaic devices.

Photocatalysts: Multichannel‐Improved Charge‐Carrier Dynamics in Well‐Designed Hetero‐nanostructural Plasmonic Photocatalysts toward Highly Efficient Solar‐to‐Fuels Conversion (Adv. Mater. 39/2015)

Well-designed hetero-nanostructural plasmonic photocatalysts with a multichannel sensitization effect on the charge-carrier dynamics process are developed by B. Dong and co-workers, as described on page 5906. The rational combination of the semiconductor heterojunction effect and a surface plasmon resonance (SPR) coupling effect of the plasmonic dimers, as well as the nanostructural property of electrospun nanofibers, results in a remarkable enhancement in the efficiency of solar to fuels conversion.