Open Access Research Article Issue
Nitrogen incorporated oxygen vacancy enriched MnCo2Ox/BiVO4 photoanodes for efficient and stable photoelectrochemical water splitting
Nano Research 2024, 17 (3): 1140-1150
Published: 26 July 2023
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Oxygen vacancies in oxygen evolution cocatalysts (OECs) can significantly improve the photoelectrochemical (PEC) water splitting performance of photoanodes. However, OECs with abundant oxygen vacancies have a poor stability when exposing to the highly-oxidizing photogenerated holes. Herein, we partly fill oxygen vacancies in a MnCo2Ox OEC with N atoms by a combined electrodeposition and sol-gel method, which dramatically improves both photocurrent density and stability of a BiVO4 photoanode. The optimized N filled oxygen vacancy-rich MnCo2Ox/BiVO4 photoanode (3 at.% of N) exhibits an outstanding photocurrent density of 6.5 mA·cm−2 at 1.23 VRHE under AM 1.5 G illumination (100 mW·cm−2), and an excellent stability of over 150 h. Systematic characterizations and theoretical calculations demonstrate that N atoms stabilize the defect structure and modulate the surface electron distribution, which significantly enhances the stability and further increases the photocurrent density. Meanwhile, other heteroatoms such as carbon, phosphorus, and sulfur are confirmed to have similar effects on improving PEC water splitting performance of photoanodes.

Research Article Issue
Nanoporous MoO3−x/BiVO4 photoanodes promoting charge separation for efficient photoelectrochemical water splitting
Nano Research 2022, 15 (8): 7026-7033
Published: 11 May 2022
Abstract PDF (4.5 MB) Collect

Owing to the relatively short hole diffusion length, severe charge recombination in the bulk of bismuth vanadate (BiVO4) is the key issue for photoelectrochemical water splitting. Herein, we design a nanoporous MoO3−x/BiVO4 heterojunction photoanode to promote charge separation. The efficient electron transport properties of oxygen deficient MoO3−x and the nanoporous structure are beneficial for charge separation, leading to a significantly enhanced PEC performance. The optimized MoO3−x/BiVO4 heterojunction photoanode exhibits a photocurrent density of 5.07 mA·cm−2 for Na2SO3 oxidation. By depositing FeOOH/NiOOH dual oxygen evolution cocatalysts to promote surface kinetics, a high photocurrent density of 4.81 mA·cm−2 can be achieved for PEC water splitting, exhibiting an excellent applied bias photon-to-current efficiency of 1.57%. Moreover, stable overall water splitting is achieved under consecutive light illumination for 10 h. We provide a proof of concept for the design of efficient BiVO4-based heterojunction photoanodes for stable PEC water splitting.

Review Article Issue
Nanoagent-based theranostic strategies against human coronaviruses
Nano Research 2022, 15 (4): 3323-3337
Published: 05 January 2022
Abstract PDF (9.2 MB) Collect

The emergence of human coronaviruses (HCoVs), especially the current pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), engender severe threats to public health globally. Despite the outstanding breakthrough of new vaccines and therapeutic medicines in the past years, HCoVs still undergo unpredictable mutations, thus demanding more effective diagnostic and therapeutic strategies. Benefitting from the unique physicochemical properties and multiple nano–bio interactions, nanomaterials hold promising potential to fight against various HCoVs, either by providing sensitive and economic nanosensors for rapid viral detection, or by developing translatable nanovaccines and broad-spectrum nanomedicines for HCoV treatment. Herein, we systemically summarized the recent applications of nanoagents in diagnostics and therapeutics for HCoV-induced diseases, as well as their limitations and perspectives against HCoV variants. We believe this review will promote the design of innovative theranostic nanoagents for the current and future HCoV-caused pandemics.

Review Article Issue
Recent progress of flexible electronics by 2D transition metal dichalcogenides
Nano Research 2022, 15 (3): 2413-2432
Published: 04 September 2021
Abstract PDF (8.8 MB) Collect

Flexible electronics is the research field with interdisciplinary crossing and integration. It shows the promising advantages of novel device configurations, low-cost and low-power consumption due to their flexible and soft characteristics. Atomic layered two-dimensional (2D) materials especially transition metal dichalcogenides, have triggered great interest in ultra-thin 2D flexible electronic devices and optoelectronic devices because of their direct and tunable bandgaps, excellent electrical, optical, mechanical, and thermal properties. This review aims to provide the recent progress in 2D TMDs and their applications in flexible electronics. The fundamental electrical properties and mechanical properties of materials, flexible device configurations, and their performance in transistors, sensors, and photodetectors are thoroughly discussed. At last, some perspectives are given on the open challenges and prospects for 2D TMDs flexible electronic devices and new device opportunities.

Research Article Issue
Observation of Bragg polaritons in monolayer tungsten disulphide
Nano Research 2022, 15 (2): 1479-1485
Published: 19 August 2021
Abstract PDF (6.7 MB) Collect

Strong light-matter interactions involved with photons and quasiparticles are fundamentally interesting to access the wealthy many-body physics in quantum mechanics. The emerging two-dimensional (2D) semiconductors with large exciton binding energies and strong quantum confinement allow to investigate exciton-photon coupling at elevated temperatures. Here we report room- temperature formation of Bragg polaritons in monolayer semiconductor on a dielectric mirror through the exciton-Bragg photon coupling. With the negative detuning energy of ~ 30 meV, angle-resolved reflection signals reveal anti-crossing behaviors of lower and upper polariton branches at ±18° together with the Rabi splitting of 10 meV. Meanwhile, the strengthened photoluminescence appears in the lower polariton branch right below the anti-crossing angles, indicating the presence of the characteristic bottleneck effect caused by the slowing exciton-polariton energy relaxation towards the band minimum. The extracted coupling strength is between the ones of weak and distinct strong coupling regimes, where the eigenenergy splitting induced by the moderate coupling is resolvable but not large enough to fully separate two polaritonic components. Our work develops a simplified strategy to generate exciton-polaritons in 2D semiconductors and can be further extended to probe the intriguing bosonic characteristics of these quasiparticles, such as Bose-Einstein condensation, polariton lasing and superfluidity, directly at the material surfaces.

Research Article Issue
Probing magnetic-proximity-effect enlarged valley splitting in monolayer WSe2 by photoluminescence
Nano Research 2018, 11 (12): 6252-6259
Published: 27 July 2018
Abstract PDF (1.3 MB) Collect

Possessing a valley degree of freedom and potential in information processing by manipulating valley features (such as valley splitting), group-VI monolayer transition metal dichalcogenides have attracted enormous interest. This valley splitting can be measured based on the difference between the peak energies of σ+ and σ- polarized emissions for excitons or trions in direct band gap monolayer transition metal dichalcogenides under perpendicular magnetic fields. In this work, a well-prepared heterostructure is formed by transferring exfoliated WSe2 onto a EuS substrate. Circular-polarization-resolved photoluminescence spectroscopy, one of the most facile and intuitive methods, is used to probe the difference of the gap energy in two valleys under an applied out-of-plane external magnetic field. Our results indicate that valley splitting can be enhanced when using a EuS substrate, as compared to a SiO2/Si substrate. The enhanced valley splitting of the WSe2/EuS heterostructure can be understood as a result of an interfacial magnetic exchange field originating from the magnetic proximity effect. The value of this magnetic exchange field, based on our estimation, is approximately 9 T. Our findings will stimulate further studies on the magnetic exchange field at the interface of similar heterostructures.

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