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Laser-engraved graphene (LEG) has been applied increasingly in flexible electronics over the past decade owing to its unique physical and chemical properties, and has shown great promise in energy controls, chemical and physical sensing, and telemedicine. In situ laser engraving has empowered graphene with additional versatilities such as miniaturized patterning, tunable composition, controllable morphology, and environmental friendliness. In this review, the technological advances of LEG from synthesis to applications in flexible and wearable electronic devices are summarized. Specifically, the use of LEG in designing next-generation nanogenerators, batteries, supercapacitors, physical sensors, gas sensors, biosensors, and wearable/telemedicine systems is discussed. An outlook related to LEG-based flexible electronics and key technological bottlenecks is identified.

Understanding and assessing endocrine response to stress is crucial to human performance analysis, stress-related disorder diagnosis, and mental health monitoring. Current approaches for stress monitoring are largely based on questionnaires, which could be very subjective. To avoid stress-inducing blood sampling and to realize continuous, non-invasive, and real-time stress analysis at the molecular levels, we investigate the dynamics of a stress hormone, cortisol, in human sweat using an integrated wireless sensing device. Highly sensitive, selective, and efficient cortisol sensing is enabled by a flexible sensor array that exploits the exceptional performance of laser-induced graphene for electrochemical sensing. Herein, we report the first cortisol diurnal cycle and the dynamic stress response profile constructed from human sweat. Our pilot study demonstrates a strong empirical correlation between serum and sweat cortisol, revealing exciting opportunities offered by sweat analysis toward non-invasive dynamic stress monitoring via wearable and portable sensing platforms.

Sodium-ion capacitors (SICs) have shown great potential to combine the merits of high-power capability of traditional capacitors and high energy capability of batteries. However, the sluggish kinetics and inferior stability of conventional sodium-ion storage anode materials are major challenges for the practical utilization of SICs. In this work, interconnected urchin-like hollow Na2Ti3O7 (Na2Ti3O7-IcUH) chains were designed and prepared by a simple one-step template-assisting method. Through a variety of controlled experiments, we explored how to effectively engineer the crystal-oriented growth and string the urchin-like spheres together. Benefiting from its urchin-like hollow structure and fully exposed (001) facet, the resulting Na2Ti3O7-IcUH exhibits a superior rate capability of 96.2 mA h g-1 at 5 A g-1. Meanwhile, the interconnected three-dimensional primary structure endows Na2Ti3O7-IcUH with excellent cyclic stability (15% capacity loss at 5 A g-1 after 2000 cycles). By coupling with commercial active carbon, the assembled SIC successfully demonstrates a energy density of 134.3 W h kg-1 at a power density of 125 W kg-1 and 38.2 W h kg-1 at a high-power density of 2500 W kg-1, as well as a superior capacity retention of 75% after 2000 cycles at 2 A g-1 within 1-4 V.

Monitoring superoxide anions in living cells have attracted much academic and biomedical interest due to their important role in metabolic processes. Herein, we confined ultra-small nano-Mn3(PO4)2 in chitosan and designed a unique puffy woven sphere consisted by nanowires. Further constructed an effective in situ detection chip using the as-synthesized nano-Mn3(PO4)2-chitosan for electrochemical sensing of superoxide anions from murine breast tumor cells (4T1). The excellent biocompatibility of chitosan and large size of the Mn3(PO4)2-chitosan spheres greatly reduced the damage and toxicity of the detection interface to the living cells, while the ultra-small nano-Mn3(PO4)2 in chitosan could effectively catalyze the superoxide anions released from cells. The nano-Mn3(PO4)2-chitosan-based sensor exhibited high sensitivity (1.6 μA μM−1), low detection limit (9.4 nM at S/N = 3) and good selectivity for O2•−. After cell culture on the surface of nano-Mn3(PO4)2-chitosan based electrode. As a miniature analytical and sensing platform, results further suggest that the prepared chip offers a more sensitive detective superoxide anions (O2•−) released from 4T1 cell lines than traditional electron paramagnetic resonance (EPR) analysis.

The photocatalytic/photoelectrocatalytic performance of nanomaterials can be enhanced by engineering a purposely designed heterojunction and a finely tuned interface electronic structure. In this featured study, we report a kind of slack ZnS–In2S3 nanonest constructed with uniform nanowires consisting of very tiny nanoparticles. Its unique microstructure created abundant heterojunctions and significantly enhanced the photocatalytic/photoelectrocatalytic performance of ZnS–In2S3 under visible light. As a photoelectrocatalyst, the ZnS–In2S3 heterojunction delivered a photocurrent density of 180 μA cm−2 at 1.23 V (vs. RHE), which is 1.5 times higher than that of pure In2S3 and far higher than that of ZnS. As a photocatalyst, the ZnS–In2S3 nanonest can completely degrade methyl orange (MO) in 20 min, which is much faster than that by pure ZnS and In2S3 under visible light. The average apparent rate of the ZnS–In2S3 heterojunction nanonest is almost four times higher than that of pure In2S3. These remarkable performances are attributed to the unique ZnS–In2S3 heterojunction, which could decrease the average free path of charge carriers and improve the charge separation efficiency.

Wearable sweat sensors have the potential to provide continuous measurements of useful biomarkers. However, current sensors cannot accurately detect low analyte concentrations, lack multimodal sensing or are difficult to fabricate at large scale. We report an entirely laser-engraved sensor for simultaneous sweat sampling, chemical sensing and vital-sign monitoring. We demonstrate continuous detection of temperature, respiration rate and low concentrations of uric acid and tyrosine, analytes associated with diseases such as gout and metabolic disorders. We test the performance of the device in both physically trained and untrained subjects under exercise and after a protein-rich diet. We also evaluate its utility for gout monitoring in patients and healthy controls through a purine-rich meal challenge. Levels of uric acid in sweat were higher in patients with gout than in healthy individuals, and a similar trend was observed in serum.

A porous g-C3N4/TiO2 with hierarchical heterostructure has been successfully fabricated through a in situ assembling of small needle-like TiO2 on the surface of ultrathin g-C3N4 sheets. The ultrathin g-C3N4 sheets with carbon vacancies and rich hydroxyl groups were found to facilitate the nucleation and in situ growth of TiO2 and also to modulate the surface chemical activity of the g-C3N4/TiO2 hierarchical heterostructure. The as-designed photocatalytic heterojunction degraded Acid Orange with 82% efficiency after 10 min under simulated solar light, and possessed excellent cycle stability. Relative physical characterizations and photochemical experiments reveal that engineering the interface/surface of g-C3N4 plays a vital role in effectively constructing heterostructures of g-C3N4/TiO2, thus realizing efficient photoinduced electron-hole separation during photocatalytic process.

Despite being pursued for a long time, hydrogen production via water splitting is still a huge challenge mainly due to a lack of durable and efficient catalysts. Molybdenum phosphide (MoP) is theoretically capable of efficient hydrogen evolution reaction (HER) catalysis, however, there is still room for further improvement in its performance. Herein, we propose a design for MoP with a P-rich outermost atomic layer for enhancing HER via complementary theoretical and experimental validation. The correlation of computational results suggests that the P-terminated surface of MoP plays a crucial role in determining its high-efficiency catalytic properties. We fabricated a P-rich outermost atomic layer of MoP nanoparticles by using N-doped porous carbon (MoP@NPCNFs) to capture more P on the surface of MoP and limit the growth of nanoparticles. Further, the as-prepared material can be directly employed as a self-supported electrocatalyst, and it exhibits remarkable electrocatalytic activity for HER in acidic media; it also reveals excellent long-term durability for up to 5,000 cycles with negligible loss of catalytic activity.

The rational construction of non-precious metals with carbonaceous material has attracted tremendous research attention with the aim to reduce the plethoric cost of platinum for catalyzing the oxygen reduction reaction (ORR). Herein, we synthesized a highly hierarchical nanostructure framework containing metal-carbon nanotubes anchored in metal embedded porous carbon spheres (M-CNTFs) and found it has similar ORR performance to that of commercial Pt-based electrocatalysts. Based on the unique hierarchical architecture, an effective platform was constructed to explore physic-chemical insights while providing guidance to search high-efficient ORR catalysts. Electrochemical measurements show that Co-CNTFs, Fe 3 C-CNTFs, and Ni-CNTFs prefer to proceed through a 4e - pathway, 2e - and 4e - mixed pathways, and a 2e - pathway, respectively. Furthermore, Co-CNTFs were found to perform better than a commercial Pt-based electrocatalyst in ORR due to its lower overpotential, excellent methanol tolerance, and superior durability. In order to understand the effects of different transition metal centers on the electrocatalytic performance of M-CNTFs, corresponding calculations were performed based on the density functional theory (DFT). Results reveal that the metal active sites and hydrophilic property of the metal-carbon system play an important role in enhancing the electrocatalytic ability, which is significant for further research on (or synthesis of) excellent catalytic materials for ORR.

Transition-metal phosphides (TMPs) have emerged as promising catalyst candidates for the hydrogen evolution reaction (HER). Although numerous methods have been investigated to obtain TMPs, most rely on traditional synthetic methods that produce materials that are inherently deficient with respect to electrical conductivity. An electrospinning-based reduction approach is presented, which generates nickel phosphide nanoparticles in N-doped porous carbon nanofibers (Ni2 P@NPCNFs) in situ. Ni2 P nanoparticles are protected from irreversible fusion and aggregation in subsequent high-temperature pyrolysis. The resistivity of Ni2 P@NPCNFs (5.34 Ω cm) is greatly decreased by 104 times compared to Ni2 P (>104 Ω cm) because N-doped carbon NFs are incorporated. As an electrocatalyst for HER, Ni2 P@NPCNFs reveal remarkable performance compared to other previously reported catalysts in acidic media. Additionally, it offers excellent catalytic ability and durability in both neutral and basic media. Encouraged by the excellent electrocatalytic performance of Ni2 P@NPCNFs, a series of pea-like Mx P@NPCNFs, including Fe2 P@NPCNFs, Co2 P@NPCNFs, and Cu3 P@NPCNFs, were synthesized by the same method. Detailed characterization suggests that the newly developed method could render combinations of ultrafine metal phosphides with porous carbon accessible; thereby, extending opportunities in electrocatalytic applications.

Hybrid ion capacitors, especially sodium ion capacitors (SICs), have recently attracted enormous attention due to their combined merits of high energy density from the battery-type anode and high power density from the capacitor-type cathode. However, achieving high-performance SICs to overcome the sluggish kinetic energy storage feature and inferior cycling stability of the battery-type anode remains a challenge. In this work, N-doped porous carbon embedded with ultrasmall titanium oxynitride nanoparticles (TiOxNy/C) was developed from metal–organic frameworks (MOFs). As the SIC anode, the as-designed TiOxNy/C exhibited a high reversible capacity (275 mA h g−1 at 50 mA g−1), ultrahigh rate capability, and superior cycling performance, which is attributed to the effective synergy between the ultrasmall TiOxNy nanoparticles and N-doped porous carbon. Furthermore, using a “two-for-one” strategy, N-doped hierarchical porous carbon (NHPC) with high surface area was prepared from TiOxNy/C by HF etching and displayed high specific capacity and rate capability when used as a SIC cathode. Considering the excellent electrochemical performances of both the anode and cathode, the as-assembled TiOxNy/C//NHPC SIC delivered a high energy density (80 W h kg−1) and high power density (4000 W kg−1).

Air pollution poses a serious threat to public health, especially in developing countries, and how to reduce it has gained great attention over the past decades. In this work, a hierarchical-structured composite, ultrafine TiO 2 encapsulated in a nitrogen-doped porous carbon framework, was fabricated and used as a photocatalyst to degrade ammonia gas. In addition, a gas sensor test system lined with a photocatalytic apparatus was proposed to estimate the degradation of ammonia gas, which allowed for facile in situ analysis and assessment of the photodegradation process of the toxic gas. Due to the large surface area, abundant pore structure, good gas adsorption property, extended light harvesting capacity and charge transfer capability of the nitrogen-doped porous carbon, the as-prepared ultrafine TiO 2 encapsulated in the nitrogen-doped porous carbon framework displayed excellent photocatalytic activity and degraded ammonia gas with 100% efficiency after only 5 min of light irradiation.

Engineering the microstructure at the atomic scale is paramount to developing effective catalysts due to the active sites and mass/charge transfer ability of catalysts severely limited by their microstructure. Herein, we nanoengineer unique necklace-like nanochains composed of molybdenum nitride embedded N-doped carbon, in which the series-wound nanochains are built from hollow beads with a very thin porous wall. MoN nanodots were downsized to 3 nm and uniformly embedded in hollow N-doped porous carbon pearls and wires. The unique hierarchical hollow cavity and ultrathin wall structure of the nanochains offer a high effective reaction chamber, more active sites, and mass/charge transfer for remarkably fast HER. The resultant MoN@NPCNCs exhibit an extremely low HER overpotential of 72 mV at 10 mA cm−2, a low Tafel slope of 53.21 mV dec−1 in an acidic solution, which is far lower than those of MoN embedded N-doped carbon nanofibers (MoN@NPCNFs, 139.21 mV vs. RHE/82.69 mV dec−1), and other previously reported MoN based catalysts. Density functional theory (DFT) calculations reveal that MoN and N-doped carbon synergistically optimizes the free energy of hydrogen adsorption on the active sites. Furthermore, this catalyst also offers an excellent electrocatalytic ability and durability in both neutral and alkaline media.

Li-Te batteries have been attracted much attention as a potential research for energy storage systems due to the overwhelming features in superior electronic conductivity and ultrahigh theoretical volumetric capacity when compared to Li-S and Li-Se batteries. The main challenge to develop Li-Te battery systems is to explore an ideal substrate for Te accommodation. Here we have designed and exploited a “muscle” structured electrode, which enables an excellent electrochemical performance. Te is confined in the hollow carbon cell as “tissue cell” and carbon nanotubes (CNTs) are induced as “blood capillary”. Such an interesting design possesses multifold advantages. Specifically, many hollow carbon cells not only offer large void space for loading Te, giving rise to high mass loading of active materials, but also manifest a good contact between Te and carbon. In addition, the introduction of CNTs provides abundant channels along CNTs in the composites for both electron and ion transport upon cycling, yielding high discharge capacity. With this desired design, muscle-like electrode shows a high specific capacity of ~ 240 mA h g -1 after 500 cycles. This work would offer new ideas for developing other exceptional electrodes for energy storage applications.

Ammonia pollution poses serious threats to public health, especially in livestock. Developing an efficient method to eliminate ammonia is critical for environmental control in agricultural livestock. Herein we fabricate a one-dimensional coaxial nanobelts of molybdenum disulfide growth on titanium dioxide encapsulated carbon nanobelts (MoS2@TiO2 CNBs) by electrospinning followed hydrothermal reaction method. The as-prepared catalysts were used to photocatalytic degradation of ammonia gas, and the experiment results show that MoS2@TiO2 CNBs displayed excellent photocatalytic activity and degraded ammonia gas with 91% efficiency after only 7 min, which mainly attributed to the synergistic effect from chemical compositions and the robust banding structure. Additionally, we propose an economical, convenient, and effective in situ analysis and monitoring method for photodegradation of ammonia, which presents promising application for further development of other high efficient photocatalysts for toxic pollutant degradation.

Activated carbons with large surface area, abundant microporosity and low cost are the most commonly used electrode materials for energy storage devices. However, activated carbons are conventionally made from fossil precursors, such as coal and petroleum, which are limited resources and easily aggregate large block in high temperature carbonization processes. In this novel work, we examined the use of rice straw as a potential alternative carbon source precursor for the production of graphene-like active carbon. A very slack activated carbon with ultra-thin two-dimensional (2D) layer structure was prepared by our proposed approach in this work, which includes a pre-treatment process and potassium hydroxide activation at high temperatures. The obtained active carbon derived from rice straw exhibited a capacitance of 255 F/g at 0.5 A/g, excellent rate capability, and long cycling capability (98% after 10,000 cycles).

Since visible-light (VL) accounting for massive solar radiation energy, a large amount of attention has been paid to the development of highly efficient visible-light-driven (VLD) semiconductor materials. However, despite recent efforts to construct VL active material, hollow structure-based silver iodide (AgI) with appropriate band gap and a large surface area are limited because of lack of a proper synthesis method. Herein, hollow AgI with p-type semiconductor behavior is constructed on the basis of micro-emulsion strategy, which enables admirable cathode photoelectrochemical (PEC) response. The as-prepared hollow AgI is applied to fabricate the PEC sensing platform and reveals a low limit of detection of 0.04 fM and a wide dynamic range up to 5 orders of magnitude toward H2S. The PEC sensing mechanism is supposed to the 'signal-off' pattern on account of the ultralow solubility product (Ksp) of Ag2S, derived from the precipitation reaction due to the high affinity between sulfide ion and Ag+. Besides, the hollow structure of AgI provides sufficient surface area forin situproducing Ag2S that serves as recombination center of carrier, thus causing the efficient quenching of photocurrent signals. This work broadens the horizon of structuring VLD semiconductor nanomaterials andKsp-based H2S sensing.

Elaborate design of efficient and stable electrocatalysts from earth-abundant elements to replace precious Pt for the hydrogen evolution reaction (HER) is an ongoing challenge. Doping metallic compounds with additional metal atoms provides the opportunity to tune their electronic and crystal structures, thus ameliorating their electrocatalytic properties. Here, we report for the first time a robust and earth-abundant Ni-doped Co3S4 catalyst grown on carbon cloth that showed high HER activity in 1 M KOH. The morphology evolution and HER activity are strongly related to the Ni substitution ratio. Electrochemical tests showed a low overpotential of 72.82 mV at 10 mA*cm-2, small Tafel slope of 49.44 mV*dec-1, and long-term durability over 46 h HER operation for the Ni0.5Co2.5S4 nanotube array self-standing on carbon cloth. These data indicate that atomic modulation of Ni plays an important role in optimizing the morphology and electrocatalytic activity by greatly expanding the active sites in the electrocatalyst. Further, the 3D self-standing nanotube array highly aids the exposure of active species and transfer of electrons and charges, substantially boosting the reaction kinetics and structure stability.

For the future of fuel cells, investigations on high activity, stable, and low-cost oxygen-reduction reaction (ORR) catalysts are critical. Transition metals have attracted particular research interest in pursuit of such efficient and sustainable ORR electrocatalysts. In this work, very tiny Co nanoparticles were assembled on 3D graphene (3DG) aerogels uniformly with the help of ascorbic acid (AA) under a facile hydrothermal process. After further thermal annealing in argon, a few carbon layers are formed and wrapped on the Co nanoparticles. The synthesized materials were primarily investigated for ORR, and the experimental results indicate that the as-prepared Co/3DG shows an obviously positive onset potential (−0.01 V) and a much higher limiting current density (5.75 mA/cm2) than Co/3DG prepared without using AA (−0.1 V, 4.6 mA/cm2). Compared with commercial 20%Pt/C, Co/3DG prepared by using AA also displayed excellent durability and superb methanol tolerance performance, which suggests that the special structure of cobalt nanoparticles wrapped with a few carbon layers and its porous 3DG aerogel support can prevent its expansion and dissolution, improve its stability largely, and provide a new way for searching excellent ORR electrocatalysts.

An oxygen reduction reaction (ORR) electrocatalyst with high performance, low cost and good durability is extremely desirable for promoting the commercial application of fuel cells. Much efforts have been made to explore efficient and nonprecious catalysts to replace the platinum-based catalyst. Particularly, cobalt oxide (Co3O4 or CoO) decorated carbon materials has been demonstrated as promising ORR electrocatalysts. In this paper, we report a kind of tiny hollow nano-Co3O4 anchored 3D graphene aerogels (3DG) in the first time, which derived from direct oxidation carbon wrapped Co/3DG through Kirkendall effect. Due to its unique structure, the hollow Co3O4/3DG shows excellent ORR catalytic activity with almost four-electron reduction pathway, high methanol tolerance and long-term durability in alkaline media.

Lithium-sulfur (Li-S) batteries are of great importance as promising electrochemical-energy storage systems in view of their overwhelming advantage of energy density. However, their commercial applications are still far away mainly due to fast capacity decay in a high sulfur content caused by low utilization of active material and severe polysulfide dissolution during electrochemical cycling. Here we have designed and prepared uniform α-Ni(OH)2 hollow spheres constructed from ultrathin nanosheets with the thickness of ~3.5 nm as a hollow sulfur nanosphere host for Li-S batteries. Specifically, the synthesized hierarchical hollow spheres not only manifest the advantages of hollow structure and robust protective shell to encapsulate a very high content of sulfur up to 81 wt%, but also offer sufficient functionalized surfaces to directly bond and entrap polysulfides in hollow sphere. When used as cathode materials for Li-S batteries, the S@Ni(OH)2 double-shell hollow hybrids exhibit a highly stable cycle life over 1000 cycles at 1 C with a very small capacity decay rate of only ~0.04% per cycle.

The authors have synthesized nanostructured manganese(II) phosphate hollow spheres [Mn3(PO4)2 HS] with tunable pore structure by using a micro-emulsion method. These, if deposited on a glassy carbon electrode (GCE), are shown to be a viable material for electrochemical sensing of superoxide (radical) anion (O2˙−) at a typical working voltage of 0.7 V (vs. SCE). Hence, they act as biomimetic enzymes that allow for the determination of O2˙− with a very low detection limit (1.35 nM), wide linear range (5 nM to 0.4 mM), and good long-term stability. The modified GCE was applied in-situ to the electrochemical determination of O2 − that is released from human malignant melanoma cells and normal keratinocyte, and it showed excellent real time analytical capability. In our perception, the use of this material offers exciting opportunities in terms of implementing nanoscale transition metal phosphates as biomimetic enzymes in enzyme-free diagnostic sensors. Conceivably, these will offer higher sensitivity and longer durability than assays based on the use of natural enzymes.

Here, we develop a novel method to successfully prepare a nanohybrid catalyst of carbon framework wrapped cobalt phosphide on carbon cloth (Co2P@C/CC) as a flexible electrocatalyst for the HER. Relative to reported phosphides phosphatized using hypophosphite, the resulting Co2P@C/CC was prepared using a Co3(PO4)2 precursor via one-step chemical vapor deposition (CVD) reduction, thus obtaining highly purified Co2P. This moderate method paves a versatile path to designing earth-abundant alternatives for the HER.

Herein, we focus on preparing a highly efficient photocatalytic material to construct a signal-on photoelectrochemical (PEC) sensing platform in view of the rigorous demand of accurate miRNA quantification. The well-dispersed Pt nanoclusters-coated copper phosphate ultrathin nanosheets (PtNCs/Cu3(PO4)2NSs) were first successfully synthesized as a photoelectrode material. Because of the ultrathin two-dimensional lamellar structure of Cu3(PO4)2NSs with a 1.3 nm thickness, as well as the homogeneous size and abundant PtNCs loaded on Cu3(PO4)2NSs, the resultant PtNCs/Cu3(PO4)2NSs were employed as a photoelectrode material for the first time and revealed outstanding photocatalytic activity in PEC sensing as a substrate. As a well-designed protocol, we realized accurate miRNA quantification via a novel signal amplification strategy based on G-wire superstructure exponentially ligating a signal probe, which possesses efficient and simple operation compared to the traditional amplification method. Moreover, the electron donor is generated in situ by lactate oxidase (Lox) labels catalyzing lactate for H2O2 production, boosting the efficient separation of electron–hole pairs for further signal amplification. Impressively, this PEC sensing platform is commendably utilized to determine miRNA-141 from prostate carcinoma cell line 22Rv1. This study, considering the excellent PtNCs/Cu3(PO4)2NSs combined with G-wire superstructure for exponential signal amplification strategy, paves a new path in biosensing and clinical diagnosis.

Monitoring superoxide anion radicals in living cells has been attracting much academic and industrial interest due to the dual roles of the radicals. Herein, we synthesized a novel nanostructured cobalt phosphate nanorods (Co3(PO4)2 NRs) with tunable pore structure using a simple and effective micro-emulsion method and explored their potential utilization in the electrochemical sensing of superoxide anions. As an analytical and sensing platform, the nanoscale biomimetic enzymes Co3(PO4)2 NRs exhibited excellent selectivity and sensitivity towards superoxide anion (O2•-) with a low detection limit (2.25nM), wide linear range (5.76-5396nM), and long-term stability. Further, the nanoscale biomimetic enzyme could be efficiently applied in situ to electrochemically detect O2•- released from human malignant melanoma cells and normal keratinocyte, showing excellent real time quantitative detection capability. This material open up exciting opportunities for implementing biomimetic enzymes in nanoscale transition metal phosphates and designing enzyme-free biosensors with much higher sensitivity and durability in health and disease analysis than those of natural one.

Novel K3V2(PO4)3 and three-dimensional conductive network K3V2(PO4)3/C nanocomposites are successfully fabricated and further evaluated as cathode materials for potassium-ion batteries for the first time. The K3V2(PO4)3/C nanocomposite exhibits a high-potential platform of 3.6–3.9 V and a good capacity retention of at least 100 cycles. This work may provide new insight into developing cathode materials for potassium-ion batteries.

The rational construction of low cost, efficient, and stable oxygen reduction reaction (ORR) electrocatalysts is important for the commercialization of fuel cells and metal–air batteries. In this article, we report an easy and effective soft-template method to in situ assemble Fe2N nanoparticles on the surface of N-doped graphene-like carbon (NC). The prepared Fe2N nanoparticles were covered by a few carbon layers, which promoted the connection of Fe–NX clusters with graphene to facilitate the formation of Fe–N–C active sites. Fe–NX and NC units were found to respectively fulfill different functionalities, and commonly afford the sample with excellent performance. The electrochemical data show that the Fe2N@NC composite with high-purity and good crystalline displays a synergistic enhanced catalytic activity for ORR, including a positive onset potential (0.084 V), a half-wave potential (−0.036 V) and a high electron transfer number (∼4e−), as compared to 20% Pt/C. Additionally, the existence of carbon shells wrapped around Fe2N nanoparticles can restrain their expansion and dissolution. In addition, the as-prepared catalyst was implemented as an air catalyst for zinc–air batteries and was found to display a comparable open circuit voltage of ca. 1.48 V and a maximum power density of 82.3 mW cm−2. These results demonstrate that the Fe2N@NC catalyst may serve as a good alternative to precious Pt for ORR in practical applications.

In this work, ultrathin graphene-like carbon nitride nanosheets with rich nanoporous and excellent hydrophilic characteristics were synthesized by a simple and effective thermal exfoliation of bulk g-C3N4. In order to fully understand the effect of thermal exfoliation conditions on the texture, surface state, and photocatalytic activity of the resulting g-C3N4, a series of exfoliated g-C3N4 were prepared by adjusting the thermal exfoliation temperature and time. The detailed characterization and analysis distinctly suggested that increasing exfoliation temperature led to a large number of nitrogen vacancies and increased specific surface area, further prolonging exfoliation time, the thermal exfoliation degree was enhanced, more carbon vacancies and enlarged pore volume formed in the resulting products. Further, the exfoliation degree and photocatalytic ability of the resultant products were enhanced by increasing thermal exfoliation temperature and time. The optimized ultrathin graphene-like carbon nitride nanosheets exhibited a 89.6% degradation efficiency for Rh6G only in 10 min, which was much faster than other such nanosheets reported in previous literature.

A novel MnO@Amorphous C-Carbon nanotubes (MnO@C-CNTs) composite is prepared by chemical vapor deposition (CVD). When used as an anode material for Li-ion batteries, the MnO@C-CNTs composite exhibits an initial discharge capacity of 1164 mA h g −1 at 100 mA g −1 and the discharge capacity gradually increased from 571.7 mA h g −1 to 654 mA h g −1 after 100 cycles at 1 A g −1 , which shows an increase of the capacity rather than attenuation. Furthermore, the MnO@C-CNTs electrode can deliver a capacity of up to 228 mA h g −1 at 5 A g −1 . These results indicate that the three-dimensional conductive network of the MnO@C-CNTs composite could prevent the aggregation of MnO particles, and its open structure allows electrolyte penetration, and reduces the diffusion path of the lithium ions, hence maximizes utilization of the electrochemically active MnO particles, while enhances the conductivity of electrode material and Li + transport. This work offers a universal approach to design various metal oxides@C-CNTs composite.

A corn-like CeO2/C coaxial cable textured by a cerium oxide shell and a carbon core was designed to sense NO. The carbon core possesses high electrical conductivity, and the CeO2 surface delivers excellent electrocatalytic activity. The sensor, typically operated at 0.8 V (vs. Ag/AgCl), exhibits a detection limit of 1.7 nM, which is 4-times lower than that of CeO2 nanotubes based one (at S/N = 3). It also displays wide linear response (up to 83 μM), a sensitivity of 0.81 μA μM−1 cm−2, and fast response (2 s). These values are highly competitive to that of a CeO2 tube (0.92 μA μM−1 cm−2 and 2 s). The sensor was used to quantify NO that is released by Aspergillus flavus.

Since the oxygen evolution catalysis process is vital yet arduous in energy conversion and storage devices, it is highly desirous but extremely challenging to engineer earth-abundant, noble-metal-free nanomaterials with superior electrocatalytic activity toward effective oxygen evolution reactions (OERs). Herein, we construct a prismlike cobalt–iron layered double hydroxide (Co–Fe LDH) with a Co/Fe ratio of 3:1 utilizing a facile self-templated strategy. Instead of carbon-species-coupled treatment, we focus on ameliorating the intrinsic properties of LDHs as OER electrocatalysts accompanied by the hierarchical nanoflake shell, well-defined interior cavity, and numerous microporous defects. In contrary to conventional LDHs synthesized via a one-pot method, Co–Fe LDHs fabricated in this work possess a huge specific surface area up to 294.1 m^2 g^(–1), which not only provides abundant active sites but also expedites the kinetics of the OER process. The as-prepared Co–Fe LDH electrocatalysts exhibit advanced electrocatalytic performance and a dramatic stability of the OER in an alkaline environment. In particular, the contribution of micropore defects is clearly discussed according to the electrochemical impedance spectroscopy analysis, in which the time constant of the OER at the micropore defect is several orders of magnitude smaller than that at the exterior of Co–Fe LDHs, forcefully verifying the intrinsic catalytic activity enhancement derived from the micropore defects. This work provides a promising model to improve OER electrocatalyst activity via produce defects and research the contribution of micropore defects.

During the development of oxygen reduction reaction electrocatalysts, transition-metal nanoparticles embedded in N-doped graphene have attracted increasing attention owing to their low-priced, minimal environmental impact, and satisfying performance. In this study, a new organic-cadmium (Cd) complex formed through Cd2+ coordination with p-phenylenediamine (PPD) was used to synthesize highly active Fe-embedded N-doped carbon catalysts for the first time. It is significant that with the decreasing molar ratio of Cd/Fe, an obvious microstructure evolution was observed in Cd-Fe-PPD from diamond-like blocks to thick flakes, and further bloomed into flowerlike shapes with ultrathin petals and then eventually exhibited large block starfish-like shapes. After carbonization, Cd was removed, slack and porous N-doped carbon was formed, and Fe was assembled in the N-doped carbon. Similar phenomenon was also observed in Co-PPD. The optimized Fe/NPC-2 material featuring uniform and well-dispersed 3-5 nm Fe nanoparticles embedded in two-dimensional ultrathin carbon nanosheets delivered excellent electrocatalytic performance ( Eonset: 0.96 V vs reversible hydrogen electrode (RHE), E1/2: 0.84 V vs RHE), which is very close to those of commercial platinum on carbon (Pt/C) ( Eonset: 0.95 V vs RHE, E1/2: 0.84 V vs RHE), and its methanol tolerance and durability also surpass those of Pt/C.

Monitoring superoxide anions in living cells have attracted much academic and biomedical interest due to their important role in metabolic processes. Herein, we confined ultra-small nano-Mn

Two-dimensional bismuth oxychloride (BiOCl) ultrathin nanoplates with a thickness of 10–20 nm are synthesized by a simple hydrothermal method. The as-prepared product is explored as an anode material for sodium-ion batteries for the first time. It shows BiOCl ultrathin nanoplates with two very suitable discharge voltage plateaus (0.6 V and 0.4 V) for sodium ion batteries. Furthermore, a two-step sodiation mechanism including an intercalation reaction and a conversion reaction is proposed. This work reveals a novel electrode material for sodium-ion batteries beyond conventional materials (such as transition metal oxides, carbon materials and alloys) and encourages more researchers to further investigate BiOCl.

A low-cost, high-performance, and durable catalyst for oxygen reduction reaction (ORR) is prerequisite for the commercialization of fuel cells. Continuous efforts are made to explore nonprecious, efficient catalysts to replace the expensive and scare platinum-based catalysts. Here, we demonstrate a kind of novel nitrogen and phosphorus co-doped mesoporous carbon spheres (NPMCS) synthesized by hydrothermal assisting pyrolysis of food yeast. The as-prepared mesoporous carbon hollow spheres exhibit a high specific surface area of 1223 m2 g−1, deliver an excellent electrocatalytic performance for ORR in alkaline media, superior durability and high resistance to methanol cross-over effect.

A glassy carbon electrode (GCE) was modified with a nanocomposite consisting of tetraoctylammonium bromide (TOAB), C60 fullerene, and palladium nanorods (PdNRs). The PdNRs were hydrothermally prepared and had a typical width of 20 ± 2 nm. The nanocomposite forms stable films on the GCE and exhibits a reversible redox pair for the C60/C60 − system while rendering the surface to be positively charged. The modified GCE was applied to fabricate an electrochemical biosensor for detecting acetylcholinesterase (AChE) by measurement of the amount of thiocholine formed from acetylthiocholine, best at a working voltage of −0.19 V (vs. SCE). The detection scheme is based on (a) measurement of the activity of ethyl paraoxon-inhibited AChE, and (b) measurement of AChE activity after reactivation with pralidoxime (2-PAM). Compared to the conventional methods using acetylthiocholine as a substrate, the dual method presented here provides data on the AChE activity after inhibition and subsequent reactivation, thereby yielding credible data on reactivated enzyme activity. The linear analytical range for AChE activity extends from 2.5 U L−1 to 250 kU·L−1, and the detection limit is 0.83 U L−1.

Recently metal-organic frameworks (MOFs) have attracted more attention in developing new electrochemical sensors due to their unique properties such as crystalline ordered structures, tunable pore sizes, large surface areas, chemical tenability and thermal stability. However, the direct application of single component MOFs in electrochemistry is limited owing to their poor electronic conductivity and inferior electrocatalytic ability. Herein, Ni(II)-Based metal-organic framework (Ni(II)-MOFs) was successfully anchored on carbon nanotubes (CNTs) by in situ solvothermal method for the first time. In the as-prepared composites, 2∼3 nm MOFs nanoparticles homogeneously dispersed on conducting CNTs allowed for the MOFs nanoparticles to be wired up to a current collector through the underlying conducting CNTs. As the electrode materials of an non-enzymatic H2O2 biosensor, the Ni(II)-MOFs/CNTs exhibited excellent electrocatalytic performance including a wide linear detection range from 0.01 to 51.6 mmol L−1, low detection limit of 2.1 μmol L−1 and very fast response of 2.5 s for H2O2 sensing. Most importantly, the stability and conductivity of Ni(II)-based MOFs is far higher than that of pure MOFs.

We report a general approach for the synthesis of yolk–shell-structured porous dicobalt phosphide/zinc oxide@porous carbon polyhedral/carbon nanotube hybrids (Co2P/ZnO@PC/CNTs) derived from bimetal–organic frameworks, and explore their potential utilization in the electrochemical sensing of superoxide anions. Beyond our expectation, the trace level of O2˙− released from living cells has also been successfully captured by our designed sensor. The presented strategy for the controlled design and synthesis of bimetal–organic frameworks-derived functional nanomaterials offers prospects of developing highly active electrocatalysts in non-enzyme sensors.

Metal-organic frameworks (MOFs) have recently attracted much interest in electrochemical fields due to their controlled porosity, large internal surface area, and countless structural topologies. However, the direct application of single component MOFs is limited since they also exhibit poor electronic conductivity, low mechanical stability, and inferior electrocatalytic ability. To overcome these problems, we implanted multi-walled carbon nanotubes (MWCNTs) into manganese-based metal-organic frameworks (Mn-BDC) using a one-step solvothermal method and found that the introduction of MWCNTs can initiate the splitting of bulky Mn-BDC into thin layers. This splitting is highly significant in that it enhances the electronic conductivity and electrocatalytic ability of Mn-BDC. The constructed Mn-BDC@MWCNT composites were utilized as an electrode modifying material in the fabrication of an electrochemical sensor and then were used successfully for the determination of biomolecules in human body fluid. The sensor displayed successful detection performance with wide linear detection ranges (0.1-1150, 0.01-500, and 0.02-1100 μM for AA, DA and UA, respectively) and low limits of detection (0.01, 0.002, and 0.005 μM for AA, DA and UA, respectively); thus, this preliminary study presents an electrochemical biosensor constructed with a novel electrode modifying material that exhibits superior potential for the practical detection of AA, DA and UA in urine samples.

A Ni-based metal-organic framework (MOF) was synthesized by a one-pot hydrothermal route and used as an anode material for lithium ion batteries (LIBs) for the first time. This Ni-based MOF has obvious ion diffusion channels which can be easily observed from its structural graph. As an anode material for LIBs, it delivers a reversible capacity of 620 mA h g −1 at a current density of 100 mA g −1 after 100 cycles. More importantly, it also shows excellent rate performance. Thus, this novel Ni-based MOF electrode will be a promising anode electrode for LIBs and further broaden the application field of MOFs materials.

Large-scale electrochemical water splitting is hindered by the sluggish oxygen evolution reaction (OER) kinetics. In this work, we report a vertically standing Fe3O4-FeSe/CoSe2 hierarchical structure material grown on carbon cloth as a highly active OER electrocatalyst. Benefiting from the rock-like Fe3O4 particles on the carbon cloth, the CoSe2 nano-arrays are more firmly affixed onto the carbon cloth. In addition, small amount of FeSe particles adsorbed on the CoSe2 arrays offer a synergistic advantage, in which CoSe2 achieved a small 279 mV overpotential at a current density of 10 mA cm−2 and a low Tafel slope of 68.78 mV dec−1. By comparing the performance of Fe3O4-FeSe/CoSe2 with pure CoSe2 and Fe3O4-FeSe, it demonstrates to be the most efficient OER catalyst. Significantly, the hierarchical structural strategy of fixed Fe3O4 growth on carbon cloth arrays introduces a new concept to explore the design of high efficiency OER electrocatalysts.

Correction for ‘Synthesis and model simulation of the hexagonal to circular transition of perovskite cesium lead halide nanosheets by rapidly changing the temperature’ by Zhong-Hai Lin et al., RSC Adv., 2020, 10, 4211–4217, DOI: 10.1039/C9RA10312K.

FePO4 is biocompatible and can act as a kind of promising enzyme mimetic. Unfortunately, the electrical conductivity of FePO4 is poor. In order to enhance its conductivity, FePO4 was embedded into nanofibers consisting of amorphous carbon and reduced graphene oxide (rGO) by an electrospinning technique. As a sensing material for monitoring superoxide anion (O2•−) and typically operated at 0.5 V (vs. SCE), it displays high sensitivity (9.6 μA⋅μM−1⋅cm−2), a low detection limit (9.7 nM at S/N = 3), a wide linear response range (10 nM to 10 μM), and fast response (1.6 s). Due to its low detection limit and fast response, the sensor in our perception has a large potential for detecting superoxide anions released by HeLa cancer cells.

A novel book-like K0.23V2O5 crystal is obtained by a simple hydrothermal method and is explored as a cathode material for Li-ion batteries for the first time. It exhibits a high reversible capacity (of ca. 244 mA h g(-1) at a current density of 50 mA g(-1)), along with a good rate capability (80 mA h g(-1) at a current density of 1800 mA g(-1)) and a good capacity retention (185.3 mA h g(-1) after 100 cycles).

Novel K2Ti8O17 is successfully fabricated via a facile hydrothermal method combined with a subsequent annealing treatment and further evaluated as an anode material for potassium-ion batteries for the first time. This study may provide a broader vision into developing anode materials for potassium-ion batteries.

In this work, we reported a novel and slack rose-like metal organic precursor designed by coordinating p-phenylenediamine with cobalt ion. After subsequent pyrolysis and acid etching process, the as-prepared Co-N-C catalyst delivered a superior catalytic activity and long-term durability. Further applied in the Zn-air battery, it also displayed a comparable performance with 20% Pt/C.

FePO