Se Vacancies Research Articles

Utilizing Se vacancies as electronic traps to synergize impedance matching and dipole polarization with ultrathin strategy to boost Fe-Se electromagnetic wave absorption

The electronic structure, transport properties and magnetic properties of the material can be adjusted by regulating the formation and concentration of anionic vacancies. In particular, materials based on transition metal chulides (TMC) have high second-order nonlinearity and atomic thin thickness, and anionic vacancy engineering can effectively achieve the optimization of material properties. However, the impact of anion vacancy engineering on dipole polarization has not been fully resolved and clarified yet, and it cannot be solely relied upon semi-empirical methods. Therefore, it is of utmost importance to deeply understand the intrinsic mechanism between vacancies and electromagnetic (EM) parameters. This knowledge will provide crucial guidance for the development of advanced electromagnetic wave (EMW) absorption materials. In this study, a novel approach is proposed for the first time, which involves the creation of Se vacancies at the heterogeneous interface formed by Fe-Se compounds. Remarkably, the generation of Se vacancies leads to an increased electron transfer from Fe to Se atoms, resulting in the formation of numerous dipolarization centers. This effect significantly enhances the material’s polarization loss capacity. Furthermore, the presence of Se vacancies acts as traps for nearby free electrons, reducing the material’s conductivity, weakening the skin effect, and improving impedance matching. The precise modulation of Se vacancies in Fe-Se compounds has led to the achievement of ultrathin characteristics and significantly enhanced EM absorption capabilities. With a thickness of only 1.5 mm, the effective absorption bandwidth (EAB) reaches 5.42 GHz, covering the Ku band, which represents a remarkable increase of 53.5 % compared to unmodified Fe-Se compounds. At a thickness of 1.3 mm, the minimum reflection loss (RL) reaches −42.4 dB, demonstrating an impressive improvement of 41.3 %. Moreover, simulations of the radar cross section (RCS) indicate that the material possesses a robust microwave attenuation ability, underscoring its great potential for practical applications.

CoFeSe2 @DMSA@FA Nanocatalyst for Amplification of Oxidative Stress to Achieve Multimodal Tumor Therapy.

Nanomedicine has significantly advanced precise tumor therapy, providing essential technical blessing for active drug accumulation, targeted consignment, and mitigation of noxious side effects. To enhance anti-tumor efficacy, the integration of multiple therapeutic modalities has garnered significant attention. Here, we designed an innovative CoFeSe2 @DMSA@FA nanocatalyst with Se vacancies (abbreviated as CFSDF), which exhibits synergistic chemodynamic therapy (CDT) and photothermal therapy (PTT), leading to amplified tumor oxidative stress and enhanced photothermal effects. The multifunctional CFSDF nanocatalyst exhibits the remarkable ability to catalyze the Fenton reaction within the acidic tumor microenvironment, efficiently converting hydrogen peroxide (H2 O2 ) into highly harmful hydroxyl radicals (⋅OH). Moreover, the nanocatalyst effectively diminishes GSH levels and ameliorates intracellular oxidative stress. The incorporation of FA modification enables CFSDF to evade immune detection and selectively target tumor tissues. Numerous in vitro and in vivo investigations have consistently demonstrated that CFSDF optimizes its individual advantages and significantly enhances therapeutic efficiency through synergistic effects of multiple therapeutic modalities, offering a valuable and effective approach to cancer treatment.

Non-stoichiometry induced 2H–1T phase interfaces and room-temperature ferromagnetism in defective molybdenum selenide

Magnetic semiconducting materials offer tremendous prospects for spin electronics but is challenging to achieve room-temperature ferromagnetism with unambiguous origin. Herein, a non-stoichiometry strategy is proposed to induce tunable magnetization in MoSe2−x nanoflowers via vacancy-controlled 2H–1T phase transition. The resultant MoSe2−x exhibits robust room-temperature ferromagnetism with significant positive correlation to the content of 1T phase and 2H–1T interfaces. Significant magnetic hysteresis and Curie transition above room temperature have been achieved, confirming the ferromagnetic feature of MoSe2−x. To examine the origin of ferromagnetism, formation energy and spin-polarized calculations have been conducted, indicating that the Se vacancy is beneficial for the formation of the 1T phase and interfacial spin polarization. Localized magnetic moments induced at the 2H–1T interfaces exhibit enhanced magnetism as compared to the net moments from the 1T orbital splitting, giving rise to strong coupling bound magnetic polarons. This work not only advances the understanding on the origin of magnetism in magnetic semiconductors, but also provides an effective route to generate ferromagnetism by defect and/or interface engineering that could be applied to multiferroics, spintronics, and valleytronics.

Disorder-induced bulk photovoltaic effect in a centrosymmetric van der Waals material

Sunlight is widely seen as one of the most abundant forms of renewable energy, with photovoltaic cells based on pn junctions being the most commonly used platform attempting to harness it. Unlike in conventional photovoltaic cells, the bulk photovoltaic effect (BPVE) allows for the generation of photocurrent and photovoltage in a single material without the need to engineer a pn junction and create a built-in electric field, thus offering a solution that can potentially exceed the Shockley–Queisser efficiency limit. However, it requires a material with no inversion symmetry and is therefore absent in centrosymmetric materials. Here, we demonstrate that breaking the inversion symmetry by structural disorder can induce BPVE in ultrathin PtSe2, a centrosymmetric semiconducting van der Waals material. Homogenous illumination of defective PtSe2 by linearly and circularly polarized light results in a photoresponse termed as linear photogalvanic effect (LPGE) and circular photogalvanic effect (CPGE), which is mostly absent in the pristine crystal. First-principles calculations reveal that LPGE originates from Se vacancies that act as asymmetric scattering centers for the photo-generated electron-hole pairs. Our work emphasizes the importance of defects to induce photovoltaic functionality in centrosymmetric materials and shows how the range of materials suitable for light sensing and energy-harvesting applications can be extended.

Engineering anion defects of ternary V-S-Se layered cathodes for ultrafast zinc ion storage

In this work, a novel stainless-steel (SS) supported lattice-mismatched V-S-Se layered compound (VSySe2−x-SS) with high selenium (Se) vacancy was synthesized by tailoring the molar ratio of S to Se. The difference between the radii of Se and S results in lattice mismatches for a large number of Se vacancies, and the highest vacancy with the ultrafast zinc (Zn) storage performance are achieved by tuning a molar ratio of sulfur (S) to Se. More interestingly, with the introduction of Se vacancies, additional redox peaks of S appear, and creates more mass-transport channels as well as active sites for Zn2+ toward fast reaction kinetics. Density functional theory (DFT) calculations confirm that the Se defects can also effectively reduce the adsorption energy of Zn2+ ions on VS0.5Se2−x-SS for more reversible adsorption/desorption process of Zn2+ ions. Consequently, the specific capacity of the VS0.5Se2−x-SS electrode is as high as 188.1 mAh g−1 after 70 cycles at 0.6 A g−1, while accomplishing an excellent rate capability and satisfactory cycle stability. In addition, an assembled flexible quasi-solid state VS0.5Se2−x-SS//Zn battery also display good cycle stability, excellent electrochemical performance, and good environmental adaptability under different malignant environments including bending, soaking, hammering, weighing, washing and cutting. This work demonstrates a facile approach for electrode modifications used in Zn2+ ion batteries, holding great promise for practical applications and shedding lights on fundamentals of defects effects on battery performance.

Boosting the sodium storage performance of iron selenides by a synergetic effect of vacancy engineering and spatial confinement

Recently, iron selenides have been considered as one of the most promising candidates for the anodes of sodium-ion batteries (SIBs) due to their cost-effectiveness and high theoretical capacity; however, their practical application is limited by poor conductivity, large volume variation and slow reaction kinetics during electrochemical reactions. In this work, spatially dual-carbon-confined VSe-Fe3Se4-xSx/FeSe2-xSx nanohybrids with abundant Se vacancies (VSe-Fe3Se4-xSx/FeSe2-xSx@NSC@rGO) are constructed via anion doping and carbon confinement engineering. The three-dimensional crosslinked carbon network composed of the nitrogen-doped carbon support derived from polyacrylic acid (PAA) and reduced graphene enhances the electronic conductivity, provides abundant channels for ion/electron transfer, ensures the structure integrity, and alleviates the agglomeration, pulverization and volume change of active material during the chemical reactions. Moreover, the introduction of S into iron selenides induces a large number of Se vacancies and regulates the electron density around iron atoms, synergistically improving the conductivity of the material and reducing the Na+ diffusion barrier. Based on the aforementioned features, the as-synthesized VSe-Fe3Se4-xSx/FeSe2-xSx@NSC@rGO electrode possesses excellent electrochemical properties, exhibiting the satisfactory specific capacity of 630.1 mA h g−1 after 160 cycles at 0.5 A/g and the reversible capacity of 319.8 mA h g−1 after 500 cycles at 3 A/g with the low-capacity attenuation of 0.016 % per cycle. This investigation provides a feasible approach to develop high-performance anodes for SIBs via a synergetic strategy of vacancy engineering and carbon confinement.

Achieving pH‐universal electrosynthesis of formate under industrial‐grade current density by enriched selenium vacancies

AbstractElectrosynthesis of formate via CO2 reduction (CO2ER) is of great significance for completing carbon cycle, however, low CO2 utilization efficiency caused by slow reaction kinetics greatly hinder its large‐scale application. Herein, we reported a ~50 nm‐thick SnSe2 nanosheets with enriched Se vacancies, which exhibits an excellent catalytic activity for pH‐universal formate electrosynthesis. In alkaline, neutral, and acidic electrolytes, this catalyst reached up to the maximum formate Faradaic efficiencies of 94.1%, 81.7%, and 78.1%, respectively. Under corresponding pH conditions, the maximum formate partial current densities achieved 800, 568, and 495 mA cm−2, respectively. Kinetic experiments combined with in situ electrochemical spectroscopy unveiled that the abundant Se vacancies promoted the dissociation of water to produce more protons, thereby accelerating the formation rate of key *OOCH intermediate. Theoretical calculations validated that the formation of enriched Sn active sites lowered the energy barrier for the *OOCH formation, eventually facilitating the formate electrosynthesis process.

SnSe2/NiSe2@N‐Doped Carbon Yolk‐Shell Heterostructure Construction and Selenium Vacancies Engineering for Ultrastable Sodium‐Ion Storage

AbstractTin diselenide, a promising anode material for sodium ion batteries (SIBs), still faces sluggish Na+ diffusion kinetics and severe volume change, resulting in undesirable cycling stability and rate capability. Heterostructure construction is an effective strategy for boosting Na+ storage of SnSe2. Herein, an appealing yolk‐shell nanostructure of SnSe2/NiSe2 heterointerface with rich Se vacancies embedded into N‐doped carbon (SnSe2/NiSe2@NC) is precisely designed through a facile hydrothermal process followed by a selenization strategy. The experimental studies coupled with theoretical calculations results verify that the heterostructure interfaces and Se vacancies accelerate the charge and Na+ transfer efficiency, improve Na+ adsorption energy and supply ample active sites. The yolk‐shell nanostructure and N‐doped carbon buffer the volume variation and improve the structural stability of the electrode material during sodium storage processes. The SnSe2/NiSe2@NC delivers ultra‐long term cycling stability (322.7 mAh g−1 after 7500 cycles at 3 A g−1) and exceptional rate capability (314.6 mAh g−1 at 10 A g−1). The Na‐ion storage mechanism of SnSe2/NiSe2@NC is explored through in situ X‐ray diffraction and ex situ high‐resolution transmission electron microscopy analysis. The present work provides an effective avenue to the rational design of heterostructure anode materials for high efficiency SIBs.

Is chemical vapor deposition of monolayer WSe2 comparable to other synthetic routes?

Chemical vapor deposition (CVD) can produce wafer-scale transition-metal dichalcogenide (TMD) monolayers for the integration of electronic and optoelectronic devices. Nonetheless, the material quality of the CVD-grown TMDs still remains controversial. Here, we compare the quality of representative WSe2 monolayers grown by CVD compared to that obtained by other synthesis methods: bulk-grown-chemical vapor transport (CVT) and flux. Through the use of a deep-learning–based algorithm to analyze atomic-resolution scanning transmission electron microscopy images, we confirm that Se vacancies (VSe) are the primary defects in WSe2, with a defect density of ∼5.3 × 1013 cm−2 in the CVD-grown sample, within the same order of magnitude of other methods (∼3.9 × 1013 cm−2 from CVT-grown samples and ∼2.7 × 1013 cm−2 from flux-grown samples). The carrier concentration in field-effect transistors at room temperature is ∼5.84 × 1012 cm−2 from a CVD-grown sample, comparable to other methods (6–7 × 1012 cm−2). The field-effect mobility of the CVD-grown sample is slightly lower than that of other synthesis methods, together with similar trends in on-current. While the difference in photoluminescence intensity is not appreciable at room temperature, different intensities of defect-related localized states appear below 60 K. We conclude that the wafer-scale CVD-grown samples can be utilized without loss of generality in the integration of electronic/optoelectronic devices.

Intermediates Regulation via Electron-Deficient Cu Sites for Selective Nitrate-to-Ammonia Electroreduction.

Ammonia (NH3 ), known as one of the fundamental raw materials for manufacturing commodities such as chemical fertilizers, dyes, ammunitions, pharmaceuticals, and textiles, exhibits a high hydrogen storage capacity of ≈17.75%. Electrochemical nitrate reduction (NO3 RR) to valuable ammonia at ambient conditions is a promising strategy to facilitate the artificial nitrogen cycle. Herein, copper-doped cobalt selenide nanosheets with selenium vacancies are reported as a robust and highly efficient electrocatalyst for the reduction of nitrate to ammonia, exhibiting a maximum Faradaic efficiency of ≈93.5% and an ammonia yield rate of 2360µg h-1 cm-2 at -0.60V versus reversible hydrogen electrode. The in situ spectroscopical and theoretical study demonstrates that the incorporation of Cu dopants and Se vacancies into cobalt selenide efficiently enhances the electron transfer from Cu to Co atoms via the bridging Se atoms, forming the electron-deficient structure at Cu sites to accelerate NO3 - dissociation and stabilize the *NO2 intermediates, eventually achieving selective catalysis in the entire NO3 RR process to produce ammonia efficiently.

Ag+ -Doped InSe Nanosheets for Membrane Electrode Assembly Electrolyzer toward Large-Current Electroreduction of CO2 to Ethanol.

It is an appealing approach to CO2 utilization through CO2 electroreduction (CO2 ER) to ethanol at high current density; however, the commonly used Cu-based catalysts cannot sustain large current during CO2 ER despite their capability for ethanol production. Herein, we report that Ag+ -doped InSe nanosheets with Se vacancies can address this grand challenge in a membrane electrode assembly (MEA) electrolyzer. As revealed by our experimental characterization and theoretical calculation, the Ag+ doping, which can tailor the electronic structure of InSe while diversifying catalytically active sites, enables the formation of key reaction intermediates and their sequential evolution into ethanol. More importantly, such a material can well work for large-current conditions in MEA electrolyzers with In2+ species stabilized via electron transfer from Ag to Se. Remarkably, in an MEA electrolyzer by coupling cathodic CO2 ER with anodic oxygen evolution reaction (OER), the optimal catalyst exhibits an ethanol Faradaic efficiency of 68.7 % and a partial current density of 186.6 mA cm-2 on the cathode with a full-cell ethanol energy efficiency of 26.1 % at 3.0 V. This work opens an avenue for large-current production of ethanol from CO2 with high selectivity and energy efficiency by rationally designing electrocatalysts.

Insight into selenium vacancies enhanced CoSe2/MoSe2 heterojunction nanosheets for hydrazine-assisted electrocatalytic water splitting

The integration of interface engineering and vacancy engineering was a feasible way to develop highly efficient electrocatalysts toward water electrolysis. Herein, we designed CoSe2/MoSe2 heterojunction nanosheets with abundant Se vacancies (VSe-CoSe2/MoSe2) for electrocatalytic water splitting. In the VSe-CoSe2/MoSe2 electrocatalyst, the electrons more easily transferred from CoSe2 to MoSe2, and interface engineering not only modulated the electronic structure, but also supplied more heterointerfaces and catalytic sites. After chemical etching, partial Se atoms were eliminated, which further activated the inert plane of the VSe-CoSe2/MoSe2 electrocatalyst and induced electron redistribution. The removal of surface Se atoms was also beneficial to expose inner reactive sites, which promoted adsorption toward reaction intermediates. Density functional theory calculations revealed that interface engineering and vacancy engineering collaboratively optimized the adsorption energy of the VSe-CoSe2/MoSe2 electrocatalyst toward the intermediate H* during the hydrogen evolution reaction process, leading to better electrocatalytic activity. The density of state diagram manifested the refined electronic structure of the VSe-CoSe2/MoSe2 electrocatalyst, and it exhibited a higher electronic state near the Fermi level, which indicated superior electronic conductivity, facilitating electron transport during the catalytic process. In alkaline media, the VSe-CoSe2/MoSe2 electrocatalyst delivered low overpotentials of merely 74 and 242 mV to obtain 10 mA cm−2 toward hydrogen evolution reaction and oxygen evolution reaction. This work illustrated the feasibility of combining two or more strategies to develop high-performance catalysts for water electrolysis.

Carrier doping of Bi[formula omitted]Se[formula omitted] surface by chemical adsorption—A DFT study

Bi2Se3 is one of the most promising topological insulators, but it suffers from intrinsic n-doping due to Se-vacancies, which shifts the Fermi level into the bulk conduction band, leading to topologically trivial carriers. Recently it was shown that this Fermi-level shift can be compensated by a locally controlled surface p-doping process, through water adsorption and XUV irradiation. Here, the microscopic mechanism of this surface doping is studied by means of density functional theory (DFT) focusing on the adsorption of H2O, OH, O, C and CH on Bi2Se3. We find that water adsorption has a negligible doping effect while hydroxyl groups lead to n-doping. Carbon adsorption on Se vacancies gives rise to p-doping but it also strongly modifies the electronic band structure around the Dirac point. Only if the Se vacancies are filled with atomic oxygen, the experimentally observed p-doping without change of the topological surface bands is reproduced. Based on the DFT results, we propose a reaction path where photon absorption gives rise to water splitting and the produced O atoms fill the Se vacancies. Adsorbed OH groups appear as intermediate states and carbon impurities may have a catalytic effect in agreement with experimental observations.

Adsorption of NO2, SO2, H2S, and NH3 on Os-Doped WSe2 Monolayers: A First-Principles Study.

In this study, DFT calculations are used to analyze the adsorption of industrial waste gases (NO2, SO2, H2S, and NH3) on WSe2 monolayers. The adsorption energy, energy band, density of states, charge transfer, and recovery time of the adsorption structures between the target gas molecules and the Os-doped WSe2 are studied. Compared with pure WSe2 monolayer, Os surface bonding doping WSe2 (Os-modified WSe2) and Os doping with Se vacancy of WSe2 (Os-embedded WSe2) exhibit improved gas molecule adsorption ability. Among them, the adsorption energy of the Os-modified WSe2 monolayer on NO2, SO2, H2S, and NH3 is greater than that of the WSe2 monolayer. At the same time, it is proved that the Os-embedded WSe2 can be used as a gas sensor for H2S and NH3 gas molecules at a high temperature.

Near‐Infrared Optical Synapses Based on Multilayer MoSe2 Moiré Superlattice for Artificial Retina

AbstractNear‐infrared (NIR) synaptic devices have attracted great attention in the field of NIR vision sensors due to their highly parallel sensing and memory functions, which emulate the basic biomimetic behaviors of the human visual system. However, it is a great challenge for the 2D material to achieve NIR light response and integration, which obstructs the progress of NIR synaptic devices. Hence, a two‐terminal NIR synaptic device based on a multilayer MoSe2 moiré superlattice is reported. The moiré structure dominated by interlayer excitons significantly enhances the interlayer coupling of multilayer MoSe2, resulting in a narrower band gap nearly to that of bulk to achieve NIR light response and broadband absorption from 240 nm to 1700 nm. The existence of Se vacancies in MoSe2 moiré superlattice makes the device show the fundamental synaptic performance. Furthermore, a 10×10 integrated retinal morphologic device array is constructed. Under the 100 s light pulse stimulation of 1060 nm, the pattern obtained after attenuation of 50 s still has a memory level of 14.84%, reflecting the excellent storage function under NIR illumination. This research opens up a new avenue for the realization of NIR artificial retina and bionic eye based on 2D materials.

Fe doping induced selenium vacancy on cobalt selenide for enhanced hydrogen peroxides production

Electrocatalytic two-electron oxygen reduction reaction (2e-ORR) pathway for hydrogen peroxides (H2O2) generation has emerges as an appealing alternative to conventional anthraquinone craft. In this work, Fe doped CoSe was synthesized via hydrothermal and subsequent high temperature (HT) annealing process. The doping of trace amount of Fe could tune the crystal growth direction and induce the generation of Se vacancy during annealing. During the Electrocatalytic measurement, the Faraday efficiency of 2e-ORR can reach 99.1%, 83.2% and 93.6% in 0.1 M KOH, 0.1 M Na2SO4, and 0.05 M H2SO4, respectively. Under the neutral condition, the production rate of H2O2 reached 18.37 mmol L−1 in 120 min. Moreover, Fe-CoSe-HT exhibits good stability and Fe2+ regeneration during flow-Fenton reaction. Hence, the dual role of selenium-vacancy-enriched Fe-CoSe-HT greatly enhanced selectivity of 2e-ORR and accelerated Fe reduction, resulting in promoted ∙OH radical generation and organic pollutants treatment.

Metal doping and vacancy synergistic induced electron/ion engineering to optimize the redox kinetics of sodium storage: A case study Mo1-xWxSe2

Transition metal dichalcogenides have emerged as potential anodes for sodium-ion batteries (SIBs) and dual-ion batteries (DIBs), but their sodium storage properties require further improvement due to their ubiquitous shortcomings including inherently poor electronic conductivity, considerable volume variations and severe structural collapse of electrodes during electrochemical reactions. Here, we report a Se vacancy-tunable Mo1-xWxSe2 embedded N-doped porous carbon superstructure (Mo1-xWxSe2/N-PC, x = 0–1) via a controllable self-assembly approach and subsequent selenization process. Varying the relative metal cation doping concentration can in situ adjust the anion Se vacancy concentration without requiring additional post-treatments. As a result, the most optimized Mo0.5W0.5Se2/N-PC for SIBs presents high capacities of 688 mAh g−1 at 0.1 A g−1 after 300 cycles. Electrochemical kinetic analysis and density functional theory calculations verify that abundant Se vacancies and metallic W doping have significant effects on improving ionic and electron diffusion kinetics. Furthermore, the DIB full cell assembled using Mo0.5W0.5Se2/N-PC anode combined with the expanded graphite cathode exhibit durable cycling stability (104 mAh g−1 at 1.0 A g−1 over 700 cycles) and outstanding rate performance (142 mAh g−1 at 4.0 A g−1). The proposed approach for fabricating tunable vacancy-modulated TMD superstructures provides an effective method for constructing advanced electrode materials for energy storage systems.

High performance and low thermal conductivity in Bi2Se3 induced by the synergistic regulation of a resonant energy level and microstructure prepared by Se slow-release method

In this study, Bi2Se3 thermoelectric materials with high density, low thermal conductivity, and excellent thermoelectric performance are prepared using a Se slow-release method. It was found that the number of Se defects in the material could be effectively reduced by changing the content of NaCl solvent, and a certain number of Na atoms are introduced into the Bi2Se3 matrix. The carrier concentration of Bi2Se3 is greatly optimized due to the synergistic effect of the two, leading to a gradual increase in the Seebeck coefficient from −94 to −122 μV K−1 at room temperature. Simultaneously, we conducted an in-depth investigation into the effects of Na doping and Se vacancies on the electronic structure of the materials. Our findings indicate that the presence of these two defects gives rise to resonance energy levels and sharpens the density of state peaks near the Fermi level. This discovery further underscores the potential for enhancing thermoelectric performance. Finally, the Bi2Se3(NaCl)10 sample achieved the maximum ZT value of 0.69 at 550 K, and the average ZT within the temperature detection range reached 0.36, increasing the thermoelectric performance of the material.

Nanohole-Array Induced Metallic Molybdenum Selenide Nanozyme for Photoenhanced Tumor-Specific Therapy.

Deficient catalytic sensitivity to the tumor microenvironment is a major obstacle to nanozyme-mediated tumor therapy. Electron transfer is the intrinsic essence for a nanozyme-catalyzed redox reaction. Here, we developed a nanohole-array-induced metallic molybdenum selenide (n-MoSe2) that is enriched with Se vacancies and can serve as an electronic transfer station for cycling electrons between H2O2 decomposition and glutathione (GSH) depletion. In a MoSe2 nanohole array, the metallic phase reaches up to 84.5%, which has been experimentally and theoretically demonstrated to exhibit ultrasensitive H2O2 responses and enhanced peroxidase (POD)-like activities for H2O2 thermodynamic heterolysis. More intriguingly, plenty of delocalized electrons appear due to phase- and vacancy-facilitated band structure reconstruction. Combined with the limited characteristic sizes of nanoholes, the surface plasmon resonance effect can be excited, leading to the broad absorption spectrum spanning of n-MoSe2 from the visible to near-infrared region (NIR) for photothermal conversion. Under NIR laser irradiation, metallic MoSe2 is able to induce out-of-balance redox and metabolism homeostasis in the tumor region, thus significantly improving therapeutic effects. This study that takes advantage of phase and defect engineering offers inspiring insights into the development of high-efficiency photothermal nanozymes.

Selective oxidation of p-phenylenediamine for blood glucose detection enabled by Se-vacancy-rich TiSe2-x@Au nanozyme

Nanozymes with enzyme-like characteristics have drawn wide interest but the catalytic activity and substrate selectivity of nanozymes still need improvement. Herein, Se-vacancy-rich TiSe2-x@Au nanocomposites are designed and demonstrated as nanozymes. The TiSe2-x@Au nanocomposites show excellent peroxidase-like activity and the chromogenic substrate p-phenylenediamine (PPD) can be selectively oxidized to compounds that exhibit an absorption peak at 413 nm that differs from that of self-oxidation or generally oxidized species, suggesting high catalytic activity and strong substrate selectivity. Theoretical calculations reveal that the PPD adsorption geometry at Se vacancies with an adsorption energy of −3.00 eV shows a unique spatial configuration and charge distribution, thereby inhibiting the free reaction and promoting both the activity and selectivity in PPD oxidation. The TiSe2-x@Au colorimetric system exhibits a wide linear range of 0.015 mM–0.6 mM and a low detection limit of 0.0037 mM in the detection of glucose. The blood glucose detection performance for human serum samples is comparable to that of a commercial glucose meter in the hospital (relative standard deviation < 6%). Our findings demonstrate a new strategy for rapid and accurate detection of blood glucose and our results provide insights into the future design of nanozymes.