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Nitrogen dioxide (NO2) is the major reason for acid rain and respiratory illness in humans. Therefore, rapid, portable, and effective detection of NO2 is essential. Herein, a novel and simple method to construct a ZnO-SnO2 heterojunction is fabricated by pyrolysis of bimetallic metal organic frameworks. The sensitivity of ZnO-SnO2 heterojunction towards 0.2 ppm NO2 under 180 °C is 37, which is 3 times that of pure ZnO and SnO2. The construction of heterojunction speeds up the response-recovery process, and this kind of material exhibits lower detection limit. The construction of heterojunction can significantly improve the NO2 sensitivity. The selectivity, stability, and moisture resistance of ZnO-SnO2 heterojunction are carried out. This could enable the realization of highly selective and sensitive portable detection of NO2. [ABSTRACT FROM AUTHOR]

Silver sulfide (Ag 2 S) quantum dots (QDs), as a new non-toxic and environmentally friendly QD material, has been widely applied in photoelectric device. We synthesized Ag 2 S QDs by simple chemical method, and constructed quantum dot-polymer heterojunction photodetector (PD) by combining with the Poly (MEH-PPV). The addition of Ag 2 S QDs improves the light absorption capacity of MEH-PPV in the visible to near infrared range. Then the photoelectric characteristics of the heterojunction photodetector were measured. The optical responsivity and specific detectivity of the device at 405,532,808 nm were 27.5 A/W,2.19 × 1010 Jones, 23.8 A/W,1.62 × 1010 Jones, 51.7 A/W,3.23 × 1010 Jones, respectively. This work will improve the capability of vulcanized MEH-PPV for broad spectrum measurement and weak light detection. [Display omitted] • Heterojunction devices were prepared by simple chemical method. • The absorption range of hybrid devices is expanded to near infrared. • The optical responsivity of the device at 808 nm reaches 51.7 A/W. [ABSTRACT FROM AUTHOR]

Fe-based catalysts with the merits of the most abundant reserves in the crust, cheapest, and low toxicity, show significant superiorities to noble-metal catalysts for electrocatalytic water splitting. Fe 3 O 4 as a member of Fe-based catalysts has been widely used for oxygen evolution reaction (OER). However, it is rarely applied for Hydrogen evolution reaction (HER) owing to the lack of inherent active sites for hydrogen absorption. Fe−N coordination bonds can act as active sites for electrocatalytic performance. Therefore, we reasonably designed and constructed Fe 3 O 4 /g-C 3 N 4 heterojunction, where abundant Fe−N bonds acting as HER active sites were formed with the aid of rich Pyridine N of g-C 3 N 4. Activity characterization result indicates the optimized 50%-Fe 3 O 4 /g-C 3 N 4 heterojunction exhibits excellent HER performance with a low overpotential of 160 mV at 10 mA cm−2, a low Tafel slope of 77.18 mV dec−1, and outstanding cycle stability. Density functional theory (DFT) calculation demonstrates that the enhanced electrocatalytic performance stems from the Fe−N bonding interaction, which endows 50%-Fe 3 O 4 /g-C 3 N 4 with lower water dissociation barrier and a moderate Gibbs free energy of hydrogen adsorption (ΔG H*) in comparison with pristine Fe 3 O 4 and g-C 3 N 4. [Display omitted] [ABSTRACT FROM AUTHOR]

Mixed halide inorganic perovskite CsPbI 3-x Br x has attracted attention in the field of optoelectronics. As a desirable photoactive material, the application of CsPbI 2 Br in the field of photodetector (PD) remains to be explored. The synergistic passivation strategy based on Ag 2 S quantum dot (QD) aqueous solution improves the morphology of the CsPbI 2 Br perovskite film. At the same time, Ag 2 S/CsPbI 2 Br bulk heterojunction optimizes the energy level arrangement between perovskite and Au electrode, improves the carrier transmission and collection capacity, and thus improves the performance of PD. Ag 2 S/CsPbI 2 Br bulk heterojunction PD has an ultra-low dark current of 7.74 pA, an ultra-fast response speed of 2.95/3.07 μs, and a high switching ratio of 7.67 × 105. This work provides a method for the preparation of high-quality mixed halide perovskite materials and a strategy for the development of high-performance perovskite PDs based on bulk heterojunction. • The synergistic passivation strategy improves the morphology of CsPbI 2 Br. • Ag 2 S/CsPbI 2 Br optimizes the energy level arrangement. • Ultralow I dark of 7.74 pA and ultrafast response of 2.95/3.07 μs. [ABSTRACT FROM AUTHOR]

• SnS 2 /Ag 2 S heterojunctions were designed on hexagonal boron nitride films. • The responsivity of SnS 2 /Ag 2 S heterojunctions higher than Ag 2 S or SnS 2 devices. • The responsivity of SnS 2 /Ag 2 S heterojunctions under 405 nm is 4.52 A/W. Photodetectors made of single Selenium sulfide (SnS 2) or Silver sulfide (Ag 2 S) are difficult to achieve superiority in performance. Therefore, it is a good idea to prepare SnS 2 /Ag 2 S heterojunctions on hexagonal boron nitride (hBN). The responsivity (R) of SnS 2 /Ag 2 S photodetector under 405 nm laser is 4.52 A/W, the specific detectivity (D*) is 3.53 × 1011 Jones and the response speed reaches 37/50 ms. Ag 2 S quantum dots (QDs) overcome the problem of easy recombination of photogenerated carriers in SnS 2. This makes the R of SnS 2 /Ag 2 S photodetectors about three orders of magnitude higher than that of Ag 2 S or SnS 2 devices. [ABSTRACT FROM AUTHOR]

• The mixed-dimensional heterojunction PD was fabricated by the solution method. • The heterojunction facilitates the excitons dissociation and carriers transfer. • The PD responsivity is 66 A/W and the specific detectivity is 1.17 × 1011 Jones. The high-performance photodetector (PD) based on mixed-dimensional (0D/3D) CsPbBr 3 /CsPbI 2 Br heterojunction was fabricated by the solution method. As a sensitizer, CsPbBr 3 can enhance light absorption, and the heterojunction promotes the process of exciton dissociation and carrier transfer, thus improving the comprehensive performance of PD. Under 405 nm irradiation, responsivity and specific detectivity of the device are 66 A/W and 1.17 × 1011 Jones. This work provides a feasible strategy for heterojunction devices based on perovskite. [ABSTRACT FROM AUTHOR]