Guihuan Chen

Fabrication of Ultrathin Bi2S3 Nanosheets for High‐Performance, Flexible, Visible–NIR Photodetectors

Ultrathin Bi2 S3 nanosheets with thicknesses down to 2.2 nm are fabricated. The resultant ultrathin Bi2 S3 -based photoconductor shows high sensitivity to visible-near infrared light from 405 to 780 nm with a high external photoresponsivity up to 4.4 A W(-1) , high detectivity of ≈10(11) Jones, relatively fast response time of ≈10 μs, and high flexibility and durability.

Cu2−xSe nanooctahedra: controllable synthesis and optoelectronic properties

Single crystalline copper selenide (Cu2−xSe) nanocrystals (NCs) with well-defined octahedral morphology are successfully synthesized by a colloidal hot-solution injection method from the reaction of anhydrous CuCl with Ph2Se2 under argon flow, in which 1-octadecene (ODE) and oleylamine (OAm) are used as solvent and surfactant, respectively. The Cu2−xSe octahedral nanostructures are characterized by XRD, SEM, TEM, HRTEM, SAED, EDS, FT-IR and XPS and it is found that they are in the cubic phase with high quality. The growth process of the nanostructures is investigated and it is noted that reaction temperature, reaction time and capping surfactant OAm play significant roles in controlling the morphologies of the final products. Meanwhile, the current–voltage (I–V) behavior of the as-prepared octahedral Cu2−xSe nanostructures is explored for the first time and it is found that the Cu2−xSe octahedral nanostructures are promising candidates for application in photodetection and related areas.

Controlled Synthesis of Ultrathin Sb2Se3 Nanowires and Application for Flexible Photodetectors.

A new solvothermal approach is introduced to synthesize ultrathin Sb2Se3 nanowires with diameters ranging from 10 to 20 nm and with length up to 30 μm. The Sb2Se3 nanowire‐based photodetectors are firstly fabricated on polyethylene terephthalate and printing paper substrates, which exhibit excellent response to visible light with fast response time (0.18 and 0.22 s), high flexibility, and durability.

Organometallically Anisotropic Growth of Ultralong Sb2Se3 Nanowires with Highly Enhanced Photothermal Response

Ultralong orthorhombic Sb2Se3 nanowires have been successfully fabricated via an alternative facile organometallic synthetic route from the reaction of triphenylantimony(III) with dibenzyldiselenide in oleylamine at 180-240 °C without any other additives. The formation and growth mechanism of the Sb2Se3 nanowires is intensively investigated, and it is found that the anisotropic growth of the nanowires with almost constant diameters is resulted from the synergistic effects of the intrinsic property of the orthorhombic crystal structure and the weak binding assistance of oleylamine, and the length of the nanowires can be elongated easily by increasing reaction time in the synthetic route. Moreover, the photothermal response of the Sb2Se3 nanowires is first evaluated under illumination of UV light (320-390 nm), and it is especially noted that the Sb2Se3 nanowires exhibit highly enhanced photothermal responses (more than two times the intensity) as compared to the bulk Sb2Se3. In addition, the Sb2Se3 nanowires show excellent light-to-heat performance, which is superior to that of the nanostructured titanium dioxide and silicon powder under the same conditions.

Fast and low-temperature synthesis of one-dimensional (1D) single-crystalline SbSI microrod for high performance photodetector

A new rapid and low temperature hydrothermal process has been developed to synthesize one-dimensional (1D) single-crystalline SbSI microrods at 160 °C for 4 h with high quality. Moreover, a first individual SbSI microrod based photodetector equipped with indium–tin-oxide (ITO) electrodes is constructed on a SiO2/Si substrate. The resulting device displays a remarkable response to visible light with an on–off ratio up to 727, a detectivity of 2.3 × 108 Jones, a noise equivalent power of 1.7 × 10−10 W/Hz1/2 and fast response/recovery times (<0.3 s).

Organometallic-route synthesis, controllable growth, mechanism investigation, and surface feature of PbSe nanostructures with tunable shapes.

Lead selenide (PbSe) nanostructures with well-defined star-shaped morphology are successfully fabricated via a facile organometallic synthetic route from the reaction of tetraphenyl lead (Ph4Pb) with triphenylphosphine selenide (Ph3PSe) in dibenzylamine (DBA) with the assistance of oleic acid (OA) and oleylamine (OAm) at 220 °C for 30 min. The structure and shape of the nanocrystals are investigated by techniques of XRD, SEM, TEM, HRTEM, SAED, and EDX, and it is interesting that the obtained PbSe nanostars present Pb-rich features, although the PbSe nanostars are still in typical rock salt phase. Experimental investigations and ATR-FTIR studies demonstrate that the media of DBA, OA, and OAm with an order OA > DAB > OAm play important roles in the growth of the PbSe nanostars with well-defined shapes because the media not only serve as solvents but capping materials. The synergetic effects of the media are also favorable for the growth of PbSe nanocrystals with the well-defined star-shaped morphologies in the current reaction system. Meanwhile, varied PbSe nanostructures with cubic, side-cut cubic, and octahedral shapes can be fabricated by regulating the relevant reaction conditions, and all of these nanostructures prepared in the procedures demonstrate Pb-rich features due to the selective capping effects of the media to the exposed Pb(II) ions. It is confirmed that the specific shape and geometry of the nanostructures can be tuned by controlling the exposed crystal surfaces and/or the corresponding compositions via the variation of reaction conditions in the media.

Organometallic Synthesis, Structure Determination, Shape Evolution, and Formation Mechanism of Hexapod-like Ternary PbSexS1–x Nanostructures with Tunable Compositions

The fabrication of hexapod-like ternary PbSexS1-x nanostructures has been reported via an alternative organometallic route from reaction of Pb(II) salt with triphenylphosphine selenide (Ph3PSe) and dibenzyl disulfide (DBDS) in dibenzylamine (DBA) with addition of oleic acid (OA) at 260 °C. The shape, structure, and composition of the nanostructured hexapods are investigated and determined by techniques of XRD, SEM, TEM, Raman, HRTEM, SAED, XPS, EDX, and HAADF-STEM, and the obtained ternary nanostructured hexapods are of typical rock salt phase with Pb-rich features without phase separation, and their compositions could be systematically regulated by facile variations of reaction parameters. Investigations reveal that the successful fabrication of the ternary hexapods with tunable compositions is resulted from the effective selection of Se and S sources of Ph3PSe and DBDS that have similar reactivity in the current reaction system along with small lattice mismatch between the two end members of PbSe and PbS. Generally, the relations between the composition and lattice parameters for the ternary nanostructures obtained in DBA with varied addition of OA exhibit linear slops that are consistent well with Vegards law. Interestingly, intensive investigations show that the nanostructures are mainly gradiently alloyed nanostructures with somewhat chalcogen-element segregations or disorders rather than homogeneously alloyed solid-state solutions due to kinetic limitation for short reaction time even though thermodynamics is feasible in the system, and also, high concentration of S element in the feedstocks tends to relative high density of disorders in the ternary nanostructures. Based on the revealing of the formation mechanism for the nanostructures with varied microstructures, the ternary PbSexS1-x hexapods can be tuned from gradient alloys with segregations to approximately homogeneous via enlongating reaction time. In addition, the photolysis of the nanostructures to lead oxysulfate and oxyselenate species is evidenced at ambient condition via Raman detection although they are stable at -190 °C.