In2Se3 Nanosheets Research Articles

In-Sb Covalent Bonds over Sb2Se3/In2Se3 Heterojunction for Enhanced Photoelectrochemical Water Splitting.

Antimony selenide is a promising P-type photocatalyst, but it has a large number of deep energy level defects, leading to severe carrier recombination. The construction of a heterojunction is a common way to resolve this problem. However, the conventional heterojunction system inevitably introduces interface defects. Herein, we employ in situ synthesis to epitaxially grow In2Se3 nanosheets on Sb2Se3 nanorods and form In-Sb covalent interfacial bonds. This petal-shaped heterostructure reduced interface defects and enhanced the efficiency of carrier separation and transport. In this work, the photocurrent density in the proposed Sb2Se3/In2Se3 photocathode is 0.485 mA cm-2 at 0 VRHE, which is 30 times higher than that of pristine Sb2Se3 and it has prominent long-term stability for 24 h without obvious decay. The results reveal that the synergy of the bidirectional built-in electric field constructed between In2Se3 and Sb2Se3 and the solid In-Sb interfacial bonds together build a high-efficiency transport channel for the photogenerated carriers that display enhanced photoelectrochemical (PEC) water-splitting performance. This work provides efficient guidance for reducing interface defects via the in situ synthesis and construction of interfacial bonds.

Electronic and light absorption properties of metal adsorbed In2Se3 monolayer

With its excellent optical and electrical characteristics, two-dimensional (2D) In2Se3 has a lot of potential uses in flexible electronics, photodetectors, and phase-change memory, and so on. In this study, we have systematically investigated the electronic structure and light absorption properties of a metal atom adsorbed monolayers of In2Se3 using density functional theory. The findings indicate that the most stable sites of different metal adsorbed In2Se3 monolayer materials are different. All metal atoms adsorbed In2Se3 (M-In2Se3) systems have good stability. After the adsorption of metal atoms on all M-In2Se3 systems, it can be seen by their energy band structures that all systems exhibit metallic behavior. It is illustrated that the adsorption of metal atoms can modulate the change of In2Se3 material from semiconductor to metal. Similarly, the densities of states plots show the metallic nature of the M-In2Se3 system structure and indicate that adsorbed metal atoms can change the properties of the In2Se3 material itself. And interestingly, in the M-In2Se3 system, the ultraviolet (UV) region exhibits significantly enhanced absorption peaks, demonstrating that the addition of metal atoms can improve the In2Se3 material’s ability to absorb light. Finally, reference light absorption spectrum, it is found that placing spherical metal nanoparticles on top of 100 nm thick In2Se3 nanosheets could excite the localized surface plasmon resonance. And among them, Au nanoparticles have the most impact on the localization of electric fields. It indicates that the introduction of Au significantly enhances the absorption properties of the material. This suggests that the metal atom adsorbed In2Se3 system will be favorable for its application in optical devices as well as electronic devices.

Flexible In2Se3 sensor for chemiresistive NO2 detection at room temperature

Piezoelectric semiconductors offer tremendous opportunity in nanosensors. In this work, we demonstrate the fabrication of a flexible gas sensor based on few-layer In2Se3 nanosheets synthesized by CVD, which exhibits high sensitivity to NO2 with fast response/recovery speed (3/40 s) at room temperature (RT) and a low detection limit of 71 ppb. We further investigated the piezoelectric effect by mechanical deformation on the sensor properties. When the deformation increased from 0.18% to 0.98%, the sensor response showed a remarkable increase and reached the maximum at 0.31%, then decreased. The improved sensing property can be ascribed to coupled effect of piezoelectricity and adsorption-induced charge transfer in the In2Se3 device. Our work opens up a way to develop new piezoelectric chemical sensors.

Piezo‐Phototronic In2Se3 Nanosheets as a Material Platform for Printable Electronics toward Multifunctional Sensing Applications

AbstractA facile, ultralow‐cost, and up‐scalable printable manufacturing process of flexible, multifunctional sensors that respond to more than one external stimulus could have a pivotal role in low‐cost wearables and portable systems for Industry 4.0. Herein, using a low capex, in‐house spray coating system, the fabrication of a low‐cost photodetector that is tuneable by mechanical strain exploiting the piezo‐phototronic nature of defect‐free 2D In2Se3 nanosheets is reported. Moreover, force sensors that respond to different levels of applied force are spray‐coated by using In2Se3 nanosheets. Regarding the photodetector, a nonmonotonic and asymmetric effect of strain on photocurrent response is shown exhibiting a local maximum at the 23°–32° compressive angle range and a slight hysteresis. Forward compressive bending leads to a photocurrent enhancement by 27% at 32° and reverse by 31% at 23°, while tensile strain leads to a current suppression by 8–10% at 23°–32° angle. The resulting force sensor repeatably demonstrates discrete piezoelectric voltages in the millivolt scale upon different mass loads, opening the path for force and tactile sensing applications. Applying industrially compatible materials for the underlying flexible substrate and electrodes, combined with spray coating, removes manufacturing complexities that engage costly and energy intensive fabrication.

Solution-processed In2Se3 nanosheets for ultrasensitive and highly selective NO2 gas sensors

Solution-processed In2Se3 nanosheets exhibit exceptional selectivity and sensitivity to NO2 gas, making them a promising candidate for gas detection systems.

Thin-Film Transistors from Electrochemically Exfoliated In2Se3 Nanosheets.

The wafer-scale fabrication of two-dimensional (2D) semiconductor thin films is the key to the preparation of large-area electronic devices. Although chemical vapor deposition (CVD) solves this problem to a certain extent, complex processes are required to realize the transfer of thin films from the growth substrate to the device substrate, not to mention its harsh reaction conditions. The solution-based synthesis and assembly of 2D semiconductors could realize the large-scale preparation of 2D semiconductor thin films economically. In this work, indium selenide (In2Se3) nanosheets with uniform sizes and thicknesses were prepared by the electrochemical intercalation of quaternary ammonium ions into bulk crystals. Layer-by-layer (LbL) assembly was used to fabricate scalable and uniform In2Se3 thin films by coordinating In2Se3 with poly(diallyldimethylammonium chloride) (PDDA). Field-effect transistors (FETs) made from a single In2Se3 flake and In2Se3 thin films showed mobilities of 12.8 cm2·V−1·s−1 and 0.4 cm2·V−1·s−1, respectively, and on/off ratios of >103. The solution self-assembled In2Se3 thin films enriches the research on wafer-scale 2D semiconductor thin films for electronics and optoelectronics and has broad prospects in high-performance and large-area flexible electronics.

Generation and interaction force analysis of loosely bound state soliton in passively mode-locked fiber laser

In this paper, the loosely bound state pulses are obtained in a passively mode-locked Er-doped fiber laser (EDFL). The microfiber-based two-dimensional In2Se3 nanosheets with a low modulation depth of ∼0.48% is chosen as the saturable absorber (SA), which is beneficial to generate bound state soliton. When the pump power increases from 83 to 450 mW, the number of the bound state soliton varies from 16 to 337, which can be attributed to the balance between the attraction from the dispersive wave (DW) and the repulsion from the gain-absorption depletion and recovery (GADR). Moreover, a subsequent theoretical simulation is also carried out to further demonstrate the experimental phenomena. In addition, the internal dynamics of pulse generation is deeply studied, which is of great significance for further understanding the bound state pulses.

Chemical vapor deposition growth of nonlayered γ-In2Se3 nanosheets on SiO2/Si substrates and its photodetector application

Two-dimensional (2D) In2Se3 with excellent optical and electrical properties has great application potential for flexible devices, photodetectors, and phase change memories. Here, we report the successes of growing In2Se3 nanosheets on SiO2/Si substrates by chemical vapor deposition (CVD) and fabricating broadband photodetector based on In2Se3. The Raman spectroscopy and transmission electron microscopy studies indicate that our 2D In2Se3 is in γ-phase. Our 2D γ-In2Se3 photodetector shows a broadband response range from near ultraviolet (350 nm) to infrared (1000 nm). The stable broadband response provides opportunities for the application of 2D γ-In2Se3-based devices and also a reference for the preparation and application of other 2D materials.

Spatially Separated Photoinduced Charge Carriers for the Enhanced Photocatalysis Over the One-Dimensional Yolk–Shell In2Se3@N-C Nanoreactor

Charge separation is crucial for applications of semiconductors in photocatalysis, especially in the field of photocatalytic organic transformation involving both the electrons and holes. Herein, we have spatially separated the photoinduced charge carriers on a nanoscale by engineering both the composition and morphology of a semiconductor-based photocatalyst. A yolk–shell nanorod structure (In2Se3@N-C YSR), which is composed of interpenetrated In2Se3 nanosheets as the core and an N-doped carbon layer as the shell, has been fabricated. This yolk–shell structure with confined cavities can provide a high surface area and multiple light reflections. The spatial distribution of the In2Se3 nanosheets and N-doped carbon layer can provide spatially separated redox-active sites, due to the existence of a controlled transfer pathway from In2Se3 to N-doped carbon layer for electrons, which can be revealed by photocurrent measurements, time-resolved photoluminescence spectra, and density functional theory (DFT) calculations. Therefore, on the basis of the above merits, the obtained In2Se3@N-C YSR has exhibited highly enhanced photocatalytic activity toward photocatalytic organic transformations, including the selective oxidation of amines to imines and the cross-dehydrogenative coupling reaction. In addition, DFT calculations have also indicated that the effective adsorption of the substrate on In2Se3@N-C also has a good influence on the photocatalytic process of organic transformation.

Remarkable bactericidal traits of a metal-ceramic composite coating elated by hierarchically structured surface.

SummaryA ceramic-based coating with a hierarchical surface structure was synthesized via solid-state reaction enabled by a double cathode glow discharge technique. This innovative coating comprises two distinct layers, specifically an outer layer with a well-aligned micro-pillar array and a dense inner layer. Both are composed of a face-centered cubic Cu(Co,Ni,Fe) solid solution phase together with a spinel-type Fe(Al,Cr)2O4 oxide. This coating exhibits superhydrophobicity and, yet, a very strong adhesion to water, i.e., the so-called “rose petal effect”. This coating also exhibits highly efficient antibacterial ability against both Staphylococcus aureus and Escherichia coli bacteria under both dark and visible light conditions. The excellent antibacterial property originates from the synergistic effects through the release of Cu ions coupled with photothermal activity upon light activation.

Incorporating Indium Selenide Nanosheets into a Polymer/Small Molecule Binary Blend Active Layer Enhances the Long-Term Stability and Performance of Its Organic Photovoltaics.

In this report, we demonstrated that the incorporation of 15 wt % two-dimensional transition-metal dichalcogenide materials indium selenide (In2Se3) nanosheets into a polymer (PM6)/small molecule (Y6) active layer not only increased its light absorption but also enhanced the long-term stability of the PM6/Y6/In2Se3 ternary blend organic photovoltaic (OPV) devices. The power conversion efficiency (PCE) of the device was improved from 15.7 to 16.5% for the corresponding PM6/Y6 binary blend device. Moreover, the PM6/Y6/In2Se3 device retained 80% of its initial PCE after thermal treatment at 100 °C for 600 h; in comparison, the binary blend device retained only 62% of its initial value. This relative enhancement of 29% resulted from the In2Se3 nanosheets retarding or facilitating molecule packing in different orientations that stabilizes the morphology of the active layer. We adopted a modified kinetics model to account for the intrinsic degradation of the OPV; the degradation-facilitated energy for the degradation kinetics of the PCE for the ternary blend device was 5.3 kJ/mol, half of that (11.3 kJ/mol) of the binary blend device, indicating a slower degradation rate occurring for the case of incorporating In2Se3 nanosheets. Therefore, the incorporation of transition metal dichalcogenide nanosheets having tunable band gaps and large asymmetric shape appears to be a new way to improve the long-term stability of devices and realize the practical use of OPVs.

High-responsivity broad-band sensing and photoconduction mechanism in direct-Gap α-In2Se3 nanosheet photodetectors

Photoconductivities (PCs) with high responsivity in two-dimensional (2D) diindium triselenide (In2Se3) nanostructures with α-phase hexagonal structure were studied. The In2Se3 nanosheet photodetectors fabricated by focused-ion beam technique exhibit broad spectral response with wavelength range from 300 nm to 1000 nm. The In2Se3 nanosheets achieve optimal responsivity of 720 A W−1 in near-infrared region (808 nm), and detectivity of 2.2 × 1012 Jones, which were higher than several 2D material photodetectors. The physical origins that result in high photoresponse in In2Se3 nanosheets such as carrier lifetime and mobility were also characterized by time-resolved PC and field-effect transistor measurements. The fast (hundred microseconds to milliseconds) and slow (seconds and longer) current rise or decay processes were both observed during the photoresponse. The narrowing (or relaxation) of depletion region and oxygen-sensitized photoconduction mechanism were suggested to be the causes of the efficient photoresponse in the In2Se3 nanostructure detectors. All these observations suggest that α-In2Se3 nanosheets could be a promising candidate for photosensitive material applications.

POLYLOL S0LUTION SYNTHESIS OF ORIENTED In2Se3 NANOSHEETS AND THEIR APPLICATION ON HIGH-PERFORMANCE INORGANIC-ORGANIC HYBRID PHOTODETECTOR

Single-phase β-In2Se3 nanosheets were successfully synthesized by hot injection method using triethylene glycol (TEG)-based solution. It was found that the adding amounts of reactant played a key role in determining size and thickness of the In2Se3 nanosheets. The In2Se3 nanosheets were (0001) orientation and had the lateral size of ~500 nm and plate thickness of ~6 nm with 0.4 mmol indium precursor. A new inorganic-organic hybrid film photodetector using the oriented In2Se3 nanosheets and photoelectronic Poly(3-hexylthiophene) (P3HT) as blending partners was fabricated on SiO2/Si wafer, exhibiting a much better photoswitching performance with a low off-current of ~40 pA at a bias voltage of 1.0 V and on/off ratio of 250 illuminated at 532 nm under incident light intensity of 40 mW/cm2 .

Piezoelectric biaxial strain effects on the optical and photoluminescence spectra of 2D III–VI compound α -In2Se3 nanosheets

The controllable biaxial strain is experimentally imposed on α-In2Se3 nanosheets by an electromechanical device. A redshift of Raman spectra is observed from the nanosheets under the strain. The Grüneisen parameter is calculated to analyze the strain effect on the vibrational behavior. Photoluminescence shows a blueshift, which can reach up to 215 meV per 1% strain. Such tunability of optical characteristics observed from α-In2Se3 nanosheets is much higher than that from conventional semiconductors. The physical mechanism behind the observation is investigated, which is related to the variations in the energy band and photoexcited carriers under a piezoelectric field and laser power.

Ultrafast Electrochemical Synthesis of Defect-Free In2 Se3 Flakes for Large-Area Optoelectronics.

Because of its thickness-dependent direct bandgap and exceptional optoelectronic properties, indium(III) selenide (In2 Se3 ) has emerged as an important semiconductor for electronics and optoelectronics. However, the scalable synthesis of defect-free In2 Se3 flakes remains a significant barrier for its practical applications. Here, a facile electrochemical strategy is presented for the ultrafast delamination of bulk layered In2 Se3 crystals in nonaqueous media, resulting in high-yield (83%) production of defect-free In2 Se3 flakes with large lateral size (up to 26 µm). The intercalation of tetrahexylammonium (THA+ ) ions mainly creates stage-3 intercalated compounds in which every three layers of In2 Se3 are occupied by one layer of THA molecules. The subsequent exfoliation leads to a majority of trilayer In2 Se3 nanosheets. As a proof of concept, solution-processed, large-area (400 µm × 20 µm) thin-film photodetectors embedded with the exfoliated In2 Se3 flakes reveal ultrafast response time with a rise and decay of 41 and 39 ms, respectively, and efficient responsivity (1 mA W-1 ). Such performance surpasses most of the state-of-the-art thin-film photodetectors based on transition metal dichalcogenides.

Lanthanide Nd ion-doped two-dimensional In2Se3 nanosheets with near-infrared luminescence property

Abstract Ultrathin two-dimensional (2D) materials have drawn great attention in recent years due to their promising applications in biomedicine and atomically optoelectronic devices. In this work, we have fabricated a 2D In2Se3 nanosheet doped with Nd3+ ions via the two-step method of solid phase synthesis and liquid exfoliation. Owing to the special inner 4f-4f energy level transitions, lanthanide ions can emit photons with almost the same energy in different environments. Here, a stable near-infrared luminescence from Nd3+-doped 2D In2Se3 nanosheets has been realized, which includes emission bands around 910, 1057, and 1324 nm. The doping of Nd3+ ions extends the emission region of In2Se3 nanosheets. Moreover, the photoluminescence mechanism of Nd3+ ions was investigated through a series of optical measurements. This work not only provides a reliable method to fabricate lanthanide ion-doped 2D materials but also possesses a great significance for luminescence study of lanthanide ions in the 2D matrix.

In2Se3 nanosheets with broadband saturable absorption used for near-infrared femtosecond laser mode locking

Indium selenide (In2Se3) has attracted tremendous attention due to its favorable electronic features, broad tunable bandgap, high stability and other attractive properties. However, its further applications for nonlinear optics have not yet been fully explored. In this work, we demonstrate that few-layer α-In2Se3 nanosheets exhibit strong saturable absorption properties over a wide wavelength range covering 800, 1064 and 1550 nm. The few-layer α-In2Se3 nanosheets used for this experiment are fabricated via a simple ultrasonic exfoliation in liquid. Stable ultrafast mode-locking laser pulses are obtained from both ytterbium-doped and erbium-doped fiber laser systems operating at 1064 and 1550 nm, respectively. A pulse duration as short as 215 fs was achieved in the Er-doped fiber laser system. Stable output pulses over 6 h of operation were obtained in both laser systems. The pulse energy and peak power of the laser output pulses were increased by reducing the In2Se3 thickness. These results indicate that α-In2Se3 nanosheets with low layer numbers are promising candidates for broad ultrafast photonics devices, such as optical switchers, Q-switchers and mode lockers.

Selective electrolysis of CO2 to CO on ultrathin In2Se3 nanosheets

Electroreduction of CO2 to fuels or valuable chemicals is a promising way to mitigate the greenhouse effect. Herein, ultrathin In2Se3 nanosheets are reported as a robust catalyst for CO2-to-CO conversion with a faradaic efficiency of 89% and a stable activity of >24 h. Theoretical investigations show that the exposed electronegative Se atoms stabilize *COOH and, thus, facilitate CO2-to-CO conversion.

Indium selenide as a saturable absorber for a wavelength-switchable vector-soliton fiber laser

We experimentally demonstrate that indium selenide (In2Se3), a III−VI group layered chalcogenide compound, can be used as a saturable absorber (SA) for a wavelength-switchable vector-soliton fiber laser. The modulation depth of the In2Se3-based SA (In2Se3-SA), fabricated by incorporating In2Se3 nanosheets with polyvinyl alcohol, is up to 14%. By inserting the In2Se3-SA into fiber laser, solitons switched at wavelengths of ~1558 and ~1530 nm, with the duration of ~1.88 and ~1.76 ps respectively, can be obtained by adjusting the polarization controller and the pump power. Further investigations demonstrate that the achieved solitons are polarization-locked vector conventional solitons, which reveals that the In2Se3 can serves as a polarization-independent SA. The results indicate that the III−VI group chalcogenide compounds, including In2Se3, could be developed as an alternative for ultrafast pulse generations, particularly, vector-soliton pulse.

Solution-Processable Two-Dimensional In2 Se3 Nanosheets as Efficient Photothermal Agents for Elimination of Bacteria.

Two-dimensional (2D) nanoflakes represent an appealing class of materials for optoelectronics applications due to their unique layered structures and excellent electronic properties. However, the lack of easy-to-manipulate and effective methods for large-scale production of these 2D materials limits their potential for applications. Also, few efforts have been made to explore their applications in biological fields. This work reports the preparation of large quantities of 2D In2 Se3 nanosheets through a solvent exfoliation technique. Transmission electron microscopy and atomic force microscopy results show that the In2 Se3 nanosheets are obtained with lateral sizes of tens of nanometers to hundreds of nanometers and thickness of 2-17 layers. Raman features coupled with the X-ray diffractometry results unequivocally confirm the as-prepared In2 Se3 nanosheets to be α phase. Moreover, these α-In2 Se3 nanosheets exhibit an excellent near-infrared (NIR) photothermal performance under an 808 nm laser irradiation. NIR photo-excitation of the α-In2 Se3 nanosheets in the presence of bacteria leads to a significant antibacterial effect, suggesting that these nanosheets have great potential to be photothermal antibacterial agents. Our work on α-In2 Se3 nanosheets presents an available method for exfoliating 2D layered materials, and highlights the potential application in chemical and biological fields of α-In2 Se3 nanosheets.