Highly responsive ultrathin GaS nanosheet photodetectors on rigid and flexible substrates.

The first GaS nanosheet-based photodetectors are demonstrated on both mechanically rigid and flexible substrates. Highly crystalline, exfoliated GaS nanosheets are promising for optoelectronics due to strong absorption in the UV-visible wavelength region. Photocurrent measurements of GaS nanosheet photodetectors made on SiO2/Si substrates and flexible polyethylene terephthalate (PET) substrates exhibit a photoresponsivity at 254 nm up to 4.2 AW(-1) and 19.2 AW(-1), respectively, which exceeds that of graphene, MoS2, or other 2D material-based devices. Additionally, the linear dynamic range of the devices on SiO2/Si and PET substrates are 97.7 dB and 78.73 dB, respectively. Both surpass that of currently exploited InGaAs photodetectors (66 dB). Theoretical modeling of the electronic structures indicates that the reduction of the effective mass at the valence band maximum (VBM) with decreasing sheet thickness enhances the carrier mobility of the GaS nanosheets, contributing to the high photocurrents. Double-peak VBMs are theoretically predicted for ultrathin GaS nanosheets (thickness less than five monolayers), which is found to promote photon absorption. These theoretical and experimental results show that GaS nanosheets are promising materials for high-performance photodetectors on both conventional silicon and flexible substrates.

Synthesis of few-layer GaSe nanosheets for high performance photodetectors.

Two-dimensional (2D) semiconductor nanomaterials hold great promises for future electronics and optics. In this paper, a 2D nanosheets of ultrathin GaSe has been prepared by using mechanical cleavage and solvent exfoliation method. Single- and few-layer GaSe nanosheets are exfoliated on an SiO(2)/Si substrate and characterized by atomic force microscopy and Raman spectroscopy. Ultrathin GaSe-based photodetector shows a fast response of 0.02 s, high responsivity of 2.8 AW(-1) and high external quantum efficiency of 1367% at 254 nm, indicating that the two-dimensional nanostructure of GaSe is a new promising material for high performance photodetectors.

Network single-walled carbon nanotube biosensors for fast and highly sensitive detection of proteins.

Detection of proteins is powerfully assayed in the diagnosis of diseases. A strategy for the development of an ultrahigh sensitivity biosensor based on a network single-walled carbon nanotube (SWNT) field-effect transistor (FET) has been demonstrated. Metallic SWNTs (m-SWNTs) in the network nanotube FET were selectively removed or cut via a carefully controlled procedure of electrical break-down (BD), and left non-conducting m-SWNTs which magnified the Schottky barrier (SB) area. This nanotube FET exhibited ultrahigh sensitivity and fast response to biomolecules. The lowest detection limit of 0.5 pM was achieved by exploiting streptavidin (SA) or a biotin/SA pair as the research model, and BD-treated nanotube biosensors had a 2 × 10(4)-fold lower minimum detectable concentration than the device without BD treatment. The response time is in the range of 0.3-3 min.

Biodiesel production from waste cooking oil catalyzed by TiO2-MgO mixed oxides.

Mixed oxides of TiO(2)-MgO obtained by the sol-gel method were used to convert waste cooking oil into biodiesel. Titanium improved the stability of the catalyst because of the defects induced by the substitution of Ti ions for Mg ions in the magnesia lattice. The best catalyst was determined to be MT-1-923, which is comprised of an Mg/Ti molar ratio of 1 and calcined at 923 K, based on an assessment of the activity and stability of the catalyst. The main reaction parameters, including methanol/oil molar ratio, catalyst amount, and temperature, were investigated. The catalytic activity of MT-1-923 decreased slowly in the reuse process. After regeneration, the activity of MT-1-923 slightly increased compared with that of the fresh catalyst due to an increase in the specific surface area and average pore diameter. The mixed oxides catalyst, TiO(2)-MgO, showed good potential in large-scale biodiesel production from waste cooking oil.

[Construction of recombinant Bombyx mori nucleopolyhedrovirus by zero background Tn7 transposition].

OBJECTIVE: In order to construct a recombinant Bombyx mori Nucleopolyhedrovirus by Tn7-mediated transposition in Escherichia coli efficiently, a new zero background transposition system was developed. METHOD: The new system consisted of a conditional replication donor vector pRADM and an attTn7 site blocked E. coli containing BmNPV-Bacmid. The donor transposon vector pRADM with the replication origin derived from R6K gamma required the factor pi encoded by the pir gene to propagate in host cells. Another conditional replication plasmid pBlockA was constructed to block the attTn7 site in host E. coli genome. RESULTS: Compared with the original vector with ColE1 origin, the transposition efficiency increased from 5.7% to 66% when using conditional replication vector pRADM transposition into original BmDH10Bac. The attTn7 site blocked strain BmDH10BacdeltaTn7 resulted in a significant increase from 5.7% to 23% in the efficacy of generating recombinant BmNPV Bacmid by transposition. Furthermore, the transposition of BmDH10BacdeltaTn7 with pRADM resulted in 100% white colonies. CONCLUSION: This highly efficient and zero background transposition system provides a simple and rapid way of construction of recombinant BmNPV to express target genes or produce gene-delivery virus particles in silkworm.

Intensification of biodiesel synthesis using zigzag micro-channel reactors.

Zigzag micro-channel reactors have been fabricated and used for continuous alkali-catalyzed biodiesel synthesis. The influences of the main geometric parameters on the performance of the micro-channel reactors were experimentally studied. It has been found that the zigzag micro-channel reactor with smaller channel size and more turns produces smaller droplets which result in higher efficiency of biodiesel synthesis. Compared to conventional stirred reactors, the time for high methyl ester conversion can be shortened significantly with the methyl ester yield of 99.5% at the residence time of only 28 s by using the optimized zigzag micro-channel reactor, which also exhibits less energy consumption for the same amount of biodiesel during biodiesel synthesis. The results indicate that zigzag micro-channel reactors can be designed as compact and mini-fuel processing plant for distributive applications.