Nanosheet Heterostructure Research Articles

Synergistic effect stemming from vertically anchored seamless 2D MoSe2 nanosheets on 1D NiTiO3 nanofibers toward CO2 photoreduction

Herein, nickel titanate nanofiber/molybdenum diselenide nanosheet (NiTiO3 NF/MoSe2) heterostructures were prepared and their photocatalytic CO2 photoreduction performance was assessed. The heterostructures were synthesized via a facile two-step synthesis route combining an electrospinning technique followed by a solvothermal method. The MoSe2 nanosheets were vertically anchored to the surface of NiTiO3 NF, thereby increasing the number of exposed active edges that are pivotal to photocatalytic performance. By tuning the loading of MoSe2 in the heterostructure, the optimal condition was obtained for the fabrication of the NiTiO3 NF/MoSe2 heterojunctions. The as-prepared heterojunctions exhibited higher photocatalytic activity than pure NiTiO3 NF and MoSe2 for the photocatalytic reduction of CO2 under ultraviolet-visible light irradiation. Among the several hybrid samples, the optimal sample displayed a 6.6- and 7.7-fold enhanced production of CO (386 µmol g–1) compared with that of pure NiTiO3 NF (58 µmol g–1) and pure MoSe2 (50 µmol g–1), respectively, with overall CO2 selectivity of 86%. This enhanced photocatalytic activity was attributed to synergy created by tailored loading of MoSe2 nanosheets onto the 1D NiTiO3 NF. This hierarchical growth of MoSe2 over NiTiO3 NF provided more exposed edge sites, enhanced light absorption over the entire spectrum, and improved separation of photogenerated electrons and holes at the NiTiO3 NF/MoSe2 heterojunction interface. Such NiTiO3 NF/MoSe2 heterojunctions with broad spectral photocatalytic performance have potential applications in water splitting and water treatment.

Self-redox reaction driven in situ formation of Cu2O/Ti3C2Tx nanosheets boost the photocatalytic eradication of multi-drug resistant bacteria from infected wound

BackgroundMXenes with interesting optical and electrical properties have been attractive in biomedical applications such as antibacterial and anticancer agents, but their low photogeneration efficiency of reactive oxygen species (ROS) and poor stability are major concerns against microbial resistance.MethodsWater-dispersible single layer Ti3C2Tx-based MXene through etching tightly stacked MAX phase precursor using a minimally intensive layer delamination method. After addition of Cu(II) ions, the adsorbed Cu(II) ions underwent self-redox reactions with the surface oxygenated moieties of MXene, leading to in situ formation of Cu2O species to yield Cu2O/Ti3C2Tx nanosheets (heterostructures).ResultsUnder NIR irradiation, the Cu2O enhanced generation of electron–hole pairs, which boosted the photocatalytic production of superoxide and subsequent transformation into hydrogen peroxide. Broad-spectrum antimicrobial performance of Cu2O/Ti3C2Tx nanosheets with sharp edges is attributed to the direct contact-induced membrane disruption, localized photothermal therapy, and in situ generated cytotoxic free radicals. The minimum inhibitory concentration of Cu2O/Ti3C2Tx nanosheets reduced at least tenfold upon NIR laser irradiation compared to pristine Cu2O/Ti3C2Tx nanosheets. The Cu2O/Ti3C2Tx nanosheets were topically administrated on the methicillin-resistant Staphylococcus aureus (MRSA) infected wounds on diabetic mice.ConclusionUpon NIR illumination, Cu2O/Ti3C2Tx nanosheets eradicated MRSA and their associated biofilm to promote wound healing. The Cu2O/Ti3C2Tx nanosheets with superior catalytic and photothermal properties have a great scope as an effective antimicrobial modality for the treatment of infected wounds.Graphical

Confining ZnS/SnS2 Ultrathin Heterostructured Nanosheets in Hollow N-Doped Carbon Nanocubes as Novel Sulfur Host for Advanced Li-S Batteries.

Hollow nanostructured hosts are important scaffolds to achieve high sulfur loading, fast charge transfer, and conspicuous restraint of lithium polysulfides (LiPSs) shuttling in lithium-sulfur (Li-S) batteries. However, developing high-efficiency hollow hosts for improving utilization and conversion of aggregated sulfur in the hollow chamber remains a longstanding challenge. Herein, hollow N-doped carbon nanocubes confined petal-like ZnS/SnS2 heterostructures (ZnS/SnS2 @NC) as a conceptually novel host for Li-S batteries are reported. Specifically, compared to consubstantial hollow double-shelled hosts, the ZnS/SnS2 @NC with higher effective active surface area brings dense contact with sulfur and enhances efficient adsorption sites for binding LiPSs and accelerating their conversion. Benefiting from the unique structure and sophisticated composition, the resulting S@ZnS/SnS2 @NC cathodes exhibit 1294 mAh g-1 at 0.2 C, an ultralow capacity decay of 0.016% per cycle over 500 cycles at 1.0 C, and a high area capacity of 4.77 mAh cm-2 at 0.5 C (5.9 mg cm-2 ). Meanwhile, the performance evolution of S@ZnS/SnS2 @NC cathodes under various sulfur loadings is further investigated by using EIS, which provides the beneficial guidance to explore viable strategies further optimizing their performance. This work sheds new insights into the design of hollow nanostructured hosts with a distinguished ability to regulate LiPSs in Li-S batteries.

A novel work function tuning strategy-based ECL sensor with sulfur dots and Au NP@MoS2 nanosheet heterostructure for triple-negative breast cancer diagnosis

In this work, a novel biosensor has been developed based on the sulfur dots and Au NP@MoS2 nanosheet heterostructure. On the one hand, highly luminescent sulfur dots were prepared by the microwave-assisted synthesis method as electrochemiluminescence (ECL) emitter. On the other hand, in order to regulate the ECL signal, Au NP@MoS2 nanosheet heterostructure has been constructed. In the heterostructure, the work function of 2-D MoS2 nanosheet with excellent electronic properties was relatively low than that of Au NPs. Due to the work function tuning strategy, there were local electrophilic or nucleophilic regions in the heterostructure. The resulted self-driven charge transfer at the interface further increased the local electron density of Au NPs. Therefore, the ECL quenching effect caused by the close-range electron transfer between the sulfur dots and the Au NPs has been effectively suppressed. And the localized surface plasmon resonance (LSPR) effect of Au NPs played a primary role to amplify the ECL signal of sulfur dots. Finally, the sensing system was designed for the detection of miRNA-210 from 0.1 pM to 10 nM. The ECL sensor showed good analytical performance in the detection of triple-negative breast cancer tumor and paracancerous tissues with the recoveries ranging from 91.7% to 102.4%. The satisfactory results indicated the work function tuning strategy-based sensor with sulfur dots and Au NP@MoS2 nanosheet heterostructure possessed great potential in the ECL research and clinical analysis.

Strongly coupled carbon quantum dots/NiCo-LDHs nanosheets on carbon cloth as electrode for high performance flexible supercapacitors

NiCo-LDHs is one of the most promising electrode materials for supercapacitors. However, the intrinsic low conductivity and the volume expansion/contraction still seriously limit the application of NiCo-LDHs in supercapacitors. Herein, we constructed carbon quantum dots (CQDs)/NiCo-LDHs nanosheets heterostructures on carbon cloth (CQDs/NiCo-LDHs@CC) through a simple solvothermal method using CQDs-embedded Co-MOF as precursor. The in-situ implanting of CQDs not only can effectively improve the conductivity of the NiCo-LDHs but also boost the long-term structural stability of the flexible electrode through the morphological optimization of NiCo-LDHs. Benefit from the ingenious structural design and strong coupling between CQDs and NiCo-LDHs, the CQDs/NiCo-LDHs@CC electrode delivered a much-enhanced capacitance performance in 6 M KOH, including a large reversible specific capacitance of 2023 F g−1 (5.22 F cm−2) at 5 mA cm−2, superior rate capability with 84.3% capacitance retention at 30 mA cm−2 and excellent cycle life. The flexible asymmetric supercapacitor device exhibited an energy density of 117.8 Wh kg−1 with a power density of 528.3 W kg−1 at 2 mA cm−2 using CQDs/NiCo-LDHs@CC as positive electrode and activated CC as negative electrode. This work provides a new opportunity for the development of nanocomposites with the in-situ implanting of CQDs to construct high-performance electrodes for flexible supercapacitors.

Interfacial Engineering of Two-Dimensional MoN/MoO2 Heterostructure Nanosheets as a Bifunctional Electrocatalyst for Overall Water Splitting.

It is still a challenge to realize the dream of a hydrogen-based economy using a robust catalyst for overall water splitting. Here, we introduce two-dimensional MoN/MoO2 heterostructure nanosheets using nickel foam as a substrate for water splitting. The heterojunction formation was achieved through the partial nitriding of a Mo-based precursor to MoN in the annealing process under NH3 environment. The heterogeneous interface between MoN and MoO2 as active sites is supposed to improve the surface reaction kinetics and electronic conductivity. Therefore, an excellent performance is achieved when MoN/MoO2 is employed as both cathode and anode electrocatalysts; the corresponding cell voltages are 1.57 and 1.84 V at 10 and 100 mA cm-2 in 1 M KOH, respectively. The promising bifunctional catalytic performance of our catalyst opens up a new way for efficient electrochemical water splitting.

Highly Conductive Networks of Silver Nanosheets.

Although printed networks of semiconducting nanosheets have found success in a range of applications, conductive nanosheet networks are limited by low conductivities (<106 S m-1 ). Here, dispersions of silver nanosheets (AgNS) that can be printed into highly conductive networks are described. Using a commercial thermal inkjet printer, AgNS patterns with unannealed conductivities of up to (6.0 ± 1.1) ×106 S m-1 are printed. These networks can form electromagnetic interference shields with record shielding effectiveness of >60dB in the microwave region at thicknesses <200nm. High resolution patterns with line widths down to 10 µm are also printed using an aerosol-jet printer which, when annealed at 200 °C, display conductivity >107 S m-1 . Unlike conventional Ag-nanoparticle inks, the 2D geometry of AgNS yields smooth, short-free interfaces between electrode and active layer when used as the top electrode in vertical nanosheet heterostructures. This shows that all-printed vertical heterostructures of AgNS/WS2 /AgNS, where the top electrode is a mesh grid, function as photodetectors demonstrating that such structures can be used in optoelectronic applications that usually require transparent conductors.

Heterostructured CoP·CoMoP nanocages as advanced electrocatalysts for efficient hydrogen evolution over a wide pH range

A sustainable and environmental-friendly method to produce hydrogen with high purity is the electrochemical water splitting, but its commercialization is challenged due to lack of cost-effective electrocatalysts for hydrogen evolution reaction (HER) over a wide pH range. Herein, a series of CoP·xCoMoP heterostructured nanocages (NCs) were prepared via a dissolution-regrowth and subsequent phosphorization process using metal-organic frameworks (MOFs) as template. The three-dimensional (3D) architecture of CoP·xCoMoP is constituted by the heterostructured nanosheets composed with CoP and CoMoP phase. These noble-metal-free earth-abundant transition metal phosphide (TMP) catalysts show a pH-universal HER activity with high efficiency. Under the optimal atom ratio of Co and Mo (6:5), CoP·5CoMoP NC catalysts can deliver a current density of 10 mA cm−2 at the overpotential of 72 mV with a Tafel slope of 60.3 mV dec−1 in 1.0 M KOH solution. The same current output requires overpotential of 44 mV in 0.5 M H2SO4 solution and 151 mV in1.0 M phosphate buffered solution (PBS), respectively. The superior HER activity of CoP·5CoMoP NC catalysts can be comparable to or even better than most of noble metal-free HER electrocatalysts reported recently. In addition, CoP·5CoMoP NC catalysts also show a fairly high HER stability over a wide pH range, and their HER activity can be well kept without significant loss for long-term electrolysis. The 3D CoP·5CoMoP heterostructured catalysts hold promise as efficient and low-cost catalysts for water splitting devices over a wide pH range.

Porous hetero-structured nickel oxide/nickel phosphide nanosheets as bifunctional electrocatalyst for hydrogen production via urea electrolysis

Urea electrolysis is a promising hydrogen generation and urea-rich wastewaters treatment technology, which requires the development of highly active electrocatalysts. In this study, porous hetero-structured nanosheet electrocatalyst (NiO/Ni2P/NF), composed of crystalline NiO and Ni2P, is prepared via the in-situ acid etching and gas-phase phosphating method, and the obtained NiO/Ni2P/NF material is applied as efficient urea oxidation and hydrogen evolution catalyst for the overall splitting of urea-containing wastewaters. An electrolyzer containing NiO/Ni2P/NF||NiO/Ni2P/NF electrode pair in an alkaline urea aqueous solution requires a potential of just 1.457 V to reach a current density of 10 mA cm−2, lower than that of 1.490 V needed for a Pt/C/NF||RuO2/NF electrolyzer to operate under the same current density. The study demonstrates the synergistic effect between NiO/Ni2P nanosheets as well as their uniform pore structure formed by the Kirkendall effect, resulting in enhanced electrocatalytic performance in hydrogen production by urea electrolysis.

Photoredox coupling of benzyl alcohol oxidation with CO2 reduction over CdS/TiO2 heterostructure under visible light irradiation

Coupling CO2 photoreduction with selective organic synthesis offers a promising modus operandi to enable simultaneous utilization of photogenerated electrons and holes to realize solar fuels production and chemicals synthesis. Herein, we report a bifunctional zero-dimensional cadmium sulfide quantum dots-two-dimensional titanium dioxide nanosheets (CdS/TNS) heterostructure for photoredox-catalyzed coupling of C–C bond synthesis via selective oxidation of benzyl alcohol with CO2 photoreduction to CO under visible light. The compositing heterointerface is beneficial for the adsorption and activation of CO2, thereby promoting the photoreduction of CO2. Remarkably, the synergistic interaction between CdS and TNS tunes the selectivity of benzyl alcohol oxidation from carbonyl compound to the C–C coupled products. Mechanistic studies unveil that the generation of C–C coupled products processes via key radical •CH(OH)Ph intermediates. Theoretical simulations reveal that the weaker adsorption of •CH(OH)Ph radical over CdS/TNS than bare CdS contributes to the formation of highly selective C–C coupled products. The findings are expected to offer instructive guidance on rationally designing the dual-functional catalysts with efficient photoredox-catalyzed coupling reaction systems for integrating CO2 reduction with selective organic transformations.

Immobilization and Evaluation of Penicillin G Acylase on Hydroxy and Aldehyde Functionalized Magnetic α-Fe2O3/Fe3O4 Heterostructure Nanosheets.

Magnetic α-Fe2O3/Fe3O4 heterostructure nanosheets were fabricated via hydrothermal calcination. The activity of penicillin G acylase (PGA), which was covalently immobilized onto silica-decorated heterostructure nanosheets, achieved the highest activity of 387.03 IU/g after 18 h of incubation with 0.1 ml of PGA. In contrast, the activity of free PGA reached the highest level when the temperature was 45°C with a pH of 8.0. However, the activity of free PGA changed more dramatically than immobilized PGA as the relative conditions changed. Moreover, the Michaelis–Menten constant (Km) and reusability of immobilized PGA were also explored. The results showed that free PGA Km and maximum rate (Vmax) were 0.0274 M and 1.167 μl/min, respectively. Km and Vmax values of immobilized PGA were 0.1082 M and 1.294 μl/min, respectively. After 12 cycles of repetitive use, immobilized PGA remained approximately 66% of its initial activity, indicating that the PGA immobilized onto the heterostructure nanosheets showed better stability and reusability than free PGA.

Covalently Interconnected Polymer Dot–WS2 Nanosheet Heterostructure for Visible Light-Driven Hydrogen Production

Covalently Interconnected Polymer Dot–WS₂ Nanosheet Heterostructure for Visible Light-Driven Hydrogen Production

Heterostructured rGO/MoS2 nanocomposites toward enhancing lubrication function of industrial gear oils

Reduced graphene oxide (rGO)/molybdenum disulfide (MoS2) heterostructure nanosheets (rGO-MoS2-1) were synthesized via vertically growing of MoS2 on rGO skeleton using a facile one-pot hydrothermal method. Toward high-performance lubrication additive, the rGO-MoS2-1 in industrial gear oil shows extraordinary dispersity and stability because its steric hindrance effect restrains the aggregation and settling tendency. More importantly, its introduction can significantly reduce the friction (∼16.7%) and wear (up to 80%) under the sliding contact. The characterization and analysis on the worn surfaces reveal that good dispersion stability, the formation of rGO-MoS2-based lubrication protective film, and the lower shear strength induced by the inherent lattice mismatch between rGO and MoS2 are the key factors in the friction reduction and protection the tribo-interfaces against wear.

Interface engineering of Co2N0.67/CoMoO4 heterostructure nanosheets as a highly active electrocatalyst for overall water splitting and Zn-H2O cell

The key in developing a low-cost, high-efficiency electrocatalyst for hydrogen generation is not only cutting the cost by avoiding noble metals but also utilizing the structure–function relationship to expose the maximum amounts of active sites on the surface by increasing the interface between the active components. Here, we demonstrated full-cycle synthesis, characterization, and optimization of Co2N0.67/CoMoO4 electrocatalyst on carbon-supported by density functional theory (DFT) calculations. The DFT calculation revealed a significant charge accumulation at the interface between Co2N0.67 and CoMoO4, suggesting the possibility of a strong synergy. As expected, electrochemical studies have shown a bifunctional Co2N0.67/CoMoO4 catalyst with low overpotential and durability towards hydrogen/oxygen evolution reactions (HER/OER) in alkaline electrolytes and robust overall water splitting performance at high current densities. In addition, the optimized Co2N0.67/CoMoO4 catalyst is also used in a Zn-H2O cell and displayed a power density exceeding Pt/C with the long-term stability of up to 170 h. The excellent electrochemical performance is the outcome of the better charge mobility at the interface resulted in the unique synergy between the active components.

Photocatalytic degradation of ammonium dinitramide over novel S-scheme g-C3N4/BiOBr heterostructure nanosheets

Photocatalytic remediation of explosive wastewater pollution gradually attracts our attention owing to strict environmental protection requirements. In this study, visible light driven photocatalytic degradation of ammonium dinitramide (ADN) over the novel solvothermal-synthesized 2D/2D g-C3N4(CN)/BiOBr(BB) heterostructure nanosheets was carried out. Multiple characterization techniques confirm the successful formation of tight contact interface between BiOBr and CN nanosheets. 30CN/BB composite exhibits the superior photocatalytic activity with degradation efficiency of 95.0 %, attributing to larger effective electrochemicalsurface area (ECSA), expanded light capture range and efficient S-scheme charge transfer ability. Besides, the main active species were determined as e− and •O2−, and generation level of free radicals was detected by EPR technique. Moreover, the reactive sites and possible degradation mechanism of ADN were analyzed by DFT calculation.

Defect-rich Fe-doped NiS/MoS2 heterostructured ultrathin nanosheets for efficient overall water splitting

With the demand for efficient hydrogen/oxygen evolution reaction (HER/OER) bifunctional electrocatalysts, defect-rich two-dimensional (2D) heterostructured materials attract increasing attention due to abundant active sites and facile mass/charge transfer. However, precise manipulation of lattice defects in a 2D heterostructured material is still a challenge. Herein, through pyrolytic sulfurization of a layered Fe-doped Ni/Mo MOF precursor, a series of defect-rich Fe-doped NiS/MoS2 ultrathin nanosheets were obtained. For 0.1Fe-NiS/MoS2, abundant lattice defects induced by Fe atoms provide more water adsorption sites, and intimate interface between NiS and MoS2 can optimize the adsorption energy of a HER/OER intermediate. As a result, both HER and OER activities are significantly enhanced. The respective overpotential is 120 mV and 297 mV for the HER and OER. Small Tafel slopes of 69.0 mV dec-1 and 54.7 mV dec-1 indicate favorable electrochemical reaction kinetics. The catalytic performance of this material can be compared with those of 20% Pt/C and RuO2 catalysts and top-rated MoS2-based materials. For overall water splitting, only 1.66 V voltage is required to deliver 10 mA cm-2. Long-term stability of 0.1Fe-NiS/MoS2presents a prospect for itspractical application.

Polydopamine assisted transformation of ZnO from nanospheres to nanosheets grown in nanoporous BiVO4 films for improved photocatalytic performance

A BiVO4/ZnO nanosheet heterostructure has been fabricated on stainless steel mesh by a solid-solution drying and calcination method, during which ZnO spheres were converted to nanosheets with the aid of polydopamine.

Theoretical investigation of electronic and optical properties of the 2D-MoSe2/GaN heterostructure nanosheet

Two-dimensional (2D) metal dichalcogenides have recently fascinated the consideration of researchers due to their exceptional electronic and optical characteristics. Despite this, the higher photo-generated carrier recombination rate constrains their technical utilization. Implementing a promising approach may result in the construction of 2D heterostructures , which may improve photocatalytic activity . This article presents the electronic structure, optical, thermodynamical, and photocatalytic characteristics of MoSe 2 /GaN heterostructures. In 2D-MoSe 2 /GaN, the MoSe 2 and GaN nanosheets interact through the van der Waals forces with a binding energy of −1.72 eV. The electronic structures of the heterostructure confirm that it is a type-II indirect band-gap semiconductor with a band-gap of 1.71 eV. Work function studies revealed that the studied heterojunctions exhibit enhanced photocatalytic activity. Figure : Two-dimensional MoSe2/GaN nanosheet heterostructure. • MoSe2 and GaN sheets interact via vdW forces in the MoSe 2 /GaN heterostructure. • MoSe 2 /GaN band structure reveals a p-type semiconductor by type-II band alignment. • Optical properties are dominating in 100-plane electric polarization. • The workfunction confirms the photocatalytic behavior of the sample.

Constructing electrospun spinel NiFe2O4 nanofibers decorated with palladium ions as nanosheets heterostructure: boosting electrocatalytic activity of HER in alkaline water electrolysis.

The development of efficient electrocatalysts for the water splitting process and understanding their fundamental catalytic mechanisms are highly essential to achieving high performance in energy conversion technologies. Herein, we have synthesised spinel nickel ferrite nanofibers (NiFe2O4-NFs) via an electrospinning (ES) method followed by a carbonization process. The resultant fiber was subjected to electrocatalytic water splitting reactions in alkaline medium. The catalytic efficiency of the NiFe2O4-NFs in OER was highly satisfactory. But it is not high enough to catalyse the HER process. Hence, palladium ions were decorated as nanosheets on NiFe2O4-NFs as a heterostructure to improve the catalytic efficiency for HER. Density functional theory (DFT) confirms that the addition of palladium to NiFe2O4-NFs helps to reduce the effect of catalyst poisoning and improve the efficiency of the catalyst. In an alkaline hybrid electrolyser, the required cell voltage was observed as 1.51 V at a fixed current density of 10 mA cm-2.

Hexagonal NiMoO4-MoS2 nanosheet heterostructure as a bifunctional electrocatalyst for urea oxidation assisted overall water electrolysis

A hexagonal NiMoO4-MoS2 nanosheet heterostructure on nickel foam (NiMoO4-MoS2/NF) was synthesized by simple hydrothermal and annealing treatment.