Recent Advances in Sodium-Ion Batteries: Cathode Materials.

Emerging energy storage systems have received significant attention along with the development of renewable energy, thereby creating a green energy platform for humans. Lithium-ion batteries (LIBs) are commonly used, such as in smartphones, tablets, earphones, and electric vehicles. However, lithium has certain limitations including safety, cost-effectiveness, and environmental issues. Sodium is believed to be an ideal replacement for lithium owing to its infinite abundance, safety, low cost, environmental friendliness, and energy storage behavior similar to that of lithium. Inhered in the achievement in the development of LIBs, sodium-ion batteries (SIBs) have rapidly evolved to be commercialized. Among the cathode, anode, and electrolyte, the cathode remains a significant challenge for achieving a stable, high-rate, and high-capacity device. In this review, recent advances in the development and optimization of cathode materials, including inorganic, organometallic, and organic materials, are discussed for SIBs. In addition, the challenges and strategies for enhancing the stability and performance of SIBs are highlighted.

Advances in Hole Transport Materials for Layered Casting Solar Cells.

Huge energy consumption and running out of fossil fuels has led to the advancement of renewable sources of power, including solar, wind, and tide. Among them, solar cells have been well developed with the significant achievement of silicon solar panels, which are popularly used as windows, rooftops, public lights, etc. In order to advance the application of solar cells, a flexible type is highly required, such as layered casting solar cells (LCSCs). Organic solar cells (OSCs), perovskite solar cells (PSCs), or dye-sensitive solar cells (DSSCs) are promising LCSCs for broadening the application of solar energy to many types of surfaces. LCSCs would be cost-effective, enable large-scale production, are highly efficient, and stable. Each layer of an LCSC is important for building the complete structure of a solar cell. Within the cell structure (active material, charge carrier transport layer, electrodes), hole transport layers (HTLs) play an important role in transporting holes to the anode. Recently, diverse HTLs from inorganic, organic, and organometallic materials have emerged to have a great impact on the stability, lifetime, and performance of OSC, PSC, or DSSC devices. This review summarizes the recent advances in the development of inorganic, organic, and organometallic HTLs for solar cells. Perspectives and challenges for HTL development and improvement are also highlighted.

Iron-Vanadium Incorporated Ferrocyanides as Potential Cathode Materials for Application in Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are potential replacements for lithium-ion batteries owing to their comparable energy density and the abundance of sodium. However, the low potential and low stability of their cathode materials have prevented their commercialization. Prussian blue analogs are ideal cathode materials for SIBs owing to the numerous diffusion channels in their 3D structure and their high potential vs. Na/Na+. In this study, we fabricated various Fe-V-incorporated hexacyanoferrates, which are Prussian blue analogs, via a one-step synthesis. These compounds changed their colors from blue to green to yellow with increasing amounts of incorporated V ions. The X-ray photoelectron spectroscopy spectrum revealed that V3+ was oxidized to V4+ in the cubic Prussian blue structure, which enhanced the electrochemical stability and increased the voltage platform. The vanadium ferrocyanide Prussian blue (VFPB1) electrode, which contains V4+ and Fe2+ in the Prussian blue structure, showed Na insertion/extraction potential of 3.26/3.65 V vs. Na/Na+. The cycling test revealed a stable capacity of ~70 mAh g-1 at a rate of 50 mA g-1 and a capacity retention of 82.5% after 100 cycles. We believe that this Fe-V-incorporated Prussian green cathode material is a promising candidate for stable and high-voltage cathodes for SIBs.

Vanadium Ferrocyanides as a Highly Stable Cathode for Lithium-Ion Batteries.

Owing to their high redox potential and availability of numerous diffusion channels in metal-organic frameworks, Prussian blue analogs (PBAs) are attractive for metal ion storage applications. Recently, vanadium ferrocyanides (VFCN) have received a great deal of attention for application in sodium-ion batteries, as they demonstrate a stable capacity with high redox potential of ~3.3 V vs. Na/Na+. Nevertheless, there have been no reports on the application of VFCN in lithium-ion batteries (LIBs). In this work, a facile synthesis of VFCN was performed using a simple solvothermal method under ambient air conditions through the redox reaction of VCl3 with K3[Fe(CN)6]. VFCN exhibited a high redox potential of ~3.7 V vs. Li/Li+ and a reversible capacity of ~50 mAh g-1. The differential capacity plots revealed changes in the electrochemical properties of VFCN after 50 cycles, in which the low spin of Fe ions was partially converted to high spin. Ex situ X-ray diffraction measurements confirmed the unchanged VFCN structure during cycling. This demonstrated the high structural stability of VFCN. The low cost of precursors, simplicity of the process, high stability, and reversibility of VFCN suggest that it can be a candidate for large-scale production of cathode materials for LIBs.

In Situ Growth of W2C/WS2 with Carbon-Nanotube Networks for Lithium-Ion Storage.

The combination of W2C and WS2 has emerged as a promising anode material for lithium-ion batteries. W2C possesses high conductivity but the W2C/WS2-alloy nanoflowers show unstable performance because of the lack of contact with the leaves of the nanoflower. In this study, carbon nanotubes (CNTs) were employed as conductive networks for in situ growth of W2C/WS2 alloys. The analysis of X-ray diffraction patterns and scanning/transmission electron microscopy showed that the presence of CNTs affected the growth of the alloys, encouraging the formation of a stacking layer with a lattice spacing of ~7.2 Å. Therefore, this self-adjustment in the structure facilitated the insertion/desertion of lithium ions into the active materials. The bare W2C/WS2-alloy anode showed inferior performance, with a capacity retention of ~300 mAh g-1 after 100 cycles. In contrast, the WCNT01 anode delivered a highly stable capacity of ~650 mAh g-1 after 100 cycles. The calculation based on impedance spectra suggested that the presence of CNTs improved the lithium-ion diffusion coefficient to 50 times that of bare nanoflowers. These results suggest the effectiveness of small quantities of CNTs on the in situ growth of sulfides/carbide alloys: CNTs create networks for the insertion/desertion of lithium ions and improve the cyclic performance of metal-sulfide-based lithium-ion batteries.

Boron Oxide Enhancing Stability of MoS2 Anode Materials for Lithium-Ion Batteries.

Molybdenum disulfide (MoS2) is the most well-known transition metal chalcogenide for lithium storage applications because of its simple preparation process, superior optical, physical, and electrical properties, and high stability. However, recent research has shown that bare MoS2 nanosheet (NS) can be reformed to the bulk structure, and sulfur atoms can be dissolved in electrolytes or form polymeric structures, thereby preventing lithium insertion/desertion and reducing cycling performance. To enhance the electrochemical performance of the MoS2 NSs, B2O3 nanoparticles were decorated on the surface of MoS2 NSs via a sintering technique. The structure of B2O3 decorated MoS2 changed slightly with the formation of a lattice spacing of ~7.37 Å. The characterization of materials confirmed the formation of B2O3 crystals at 30% weight percentage of H3BO3 starting materials. In particular, the MoS2_B3 sample showed a stable capacity of ~500 mAh·g-1 after the first cycle. The cycling test delivered a high reversible specific capacity of ~82% of the second cycle after 100 cycles. Furthermore, the rate performance also showed a remarkable recovery capacity of ~98%. These results suggest that the use of B2O3 decorations could be a viable method for improving the stability of anode materials in lithium storage applications.

WS2-WC-WO3 nano-hollow spheres as an efficient and durable catalyst for hydrogen evolution reaction.

Transition metal dichalcogenides (TMDs), transition metal carbides (TMCs), and transition metal oxides (TMOs) have been widely investigated for electrocatalytic applications owing to their abundant active sites, high stability, good conductivity, and various other fascinating properties. Therefore, the synthesis of composites of TMDs, TMCs, and TMOs is a new avenue for the preparation of efficient electrocatalysts. Herein, we propose a novel low-cost and facile method to prepare TMD-TMC-TMO nano-hollow spheres (WS2-WC-WO3 NH) as an efficient catalyst for the hydrogen evolution reaction (HER). The crystallinity, morphology, chemical bonding, and composition of the composite material were comprehensively investigated using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The results confirmed the successful synthesis of the WS2-WC-WO3 NH spheres. Interestingly, the presence of nitrogen significantly enhanced the electrical conductivity of the hybrid material, facilitating electron transfer during the catalytic process. As a result, the WS2-WC-WO3 NH hybrid exhibited better HER performance than the pure WS2 nanoflowers, which can be attributed to the synergistic effect of the W-S, W-C, and W-O bonding in the composite. Remarkably, the Tafel slope of the WS2-WC-WO3 NH spheres was 59 mV dec-1, which is significantly lower than that of the pure WS2 NFs (82 mV dec-1). The results also confirmed the unprecedented stability and superior electrocatalytic performance of the WS2-WC-WO3 NH spheres toward the HER, which opens new avenues for the preparation of low-cost and highly effective materials for energy conversion and storage applications.

Metal salt-modified biochars derived from agro-waste for effective congo red dye removal.

Anionic Congo red dye (CR) is not effectively removed by conventional adsorbents. Three novel biochars derived from agro-waste (Acacia auriculiformis), modified with metal salts of FeCl3, AlCl3, and CaCl2 at 500 °C pyrolysis have been developed to enhance CR treatment. These biochars revealed significant differences in effluents compared to BC, which satisfied initial research expectations (P < 0.05). The salt concentration of 2 M realized optimal biochars with the highest CR removal of 96.8%, for AlCl3-biochar and FeCl3-biochar and 70.8% for CaCl2-biochar. The modified biochars were low in the specific surface area (137.25-380.78 m2 g-1) compared normal biochar (393.15 m2 g-1), had more heterogeneous particles and successfully integrated metal oxides on the surface. The CR removal increased with a decrease in pH and increase in biochar dosage, which established an optimal point at an initial loading of 25 mg g-1. Maximum adsorption capacity achieved 130.0, 44.86, and 30.80 mg g-1 for BFe, BCa, and BAl, respectively. As magnetic biochar, which is easily separated from the solution and achieves a high adsorption capacity, FeCl3-biochar is the preferred biochar for CR treatment application.

Ag Nanoparticle-Decorated MoS2 Nanosheets for Enhancing Electrochemical Performance in Lithium Storage.

Metallic phase 1T MoS2 is a well-known potential anode for enhancing the electrochemical performance of lithium-ion batteries owing to its mechanical/chemical stability and high conductivity. However, during the lithiation/delithiation process, MoS2 nanosheets (NSs) tend to restack to form bulky structures that deteriorate the cycling performance of bare MoS2 anodes. In this study, we prepared Ag nanoparticle (NP)-decorated 1T MoS2 NSs via a liquid exfoliation method with lithium intercalation and simple reduction of AgNO3 in NaBH4. Ag NPs were uniformly distributed on the MoS2 surface with the assistance of 3-mercapto propionic acid. Ag NPs with the size of a few nanometers enhanced the conductivity of the MoS2 NS and improved the electrochemical performance of the MoS2 anode. Specifically, the anode designated as Ag3@MoS2 (prepared with AgNO3 and MoS2 in a weight ratio of 1:10) exhibited the best cycling performance and delivered a reversible specific capacity of 510 mAh·g-1 (approximately 73% of the initial capacity) after 100 cycles. Moreover, the rate performance of this sample had a remarkable recovery capacity of ~100% when the current decreased from 1 to 0.1 A·g-1. The results indicate that the Ag nanoparticle-decorated 1T MoS2 can be employed as a high-rate capacity anode in lithium-ion storage applications.

W2C/WS2 Alloy Nanoflowers as Anode Materials for Lithium-Ion Storage.

Recently, composites of MXenes and two-dimensional transition metal dichalcogenides have emerged as promising materials for energy storage applications. In this study, W2C/WS2 alloy nanoflowers (NFs) were prepared by a facile hydrothermal method. The alloy NFs showed a particle size of 200 nm-1 µm, which could be controlled. The electrochemical performance of the as-prepared alloy NFs was investigated to evaluate their potential for application as lithium-ion battery (LIB) anodes. The incorporation of W2C in the WS2 NFs improved their electronic properties. Among them, the W2C/WS2_4h NF electrode showed the best electrochemical performance with an initial discharge capacity of 1040 mAh g-1 and excellent cyclability corresponding to a reversible capacity of 500 mAh g-1 after 100 cycles compared to that of the pure WS2 NF electrode. Therefore, the incorporation of W2C is a promising approach to improve the performance of LIB anode materials.

Recent Advances in the Electrochemical Sensing of Venlafaxine: An Antidepressant Drug and Environmental Contaminant.

Venlafaxine (VEN), as one of the popular anti-depressants, is widely utilized for the treatment of major depressive disorder, panic disorder, as well as anxiety. This drug influences the chemicals in the brain, which may result in imbalance in depressed individuals. However, venlafaxine and its metabolites are contaminants in water. They have exerted an adverse influence on living organisms through their migration and transformation in various forms of adsorption, photolysis, hydrolysis, and biodegradation followed by the formation of various active compounds in the environment. Hence, it is crucial to determine VEN with low concentrations in high sensitivity, specificity, and reproducibility. Some analytical techniques have been practically designed to quantify VEN. However, electroanalytical procedures have been of interest due to the superior advantages in comparison to conventional techniques, because such methods feature rapidity, simplicity, sensitivity, and affordability. Therefore, this mini-review aims to present the electrochemical determination of VEN with diverse electrodes, such as carbon paste electrodes, glassy carbon electrodes, mercury-based electrodes, screen-printed electrodes, pencil graphite electrodes, and ion-selective electrodes.

Recent Advances in TiO2-Based Photocatalysts for Reduction of CO2 to Fuels.

Titanium dioxide (TiO2) has attracted increasing attention as a candidate for the photocatalytic reduction of carbon dioxide (CO2) to convert anthropogenic CO2 gas into fuels combined with storage of intermittent and renewable solar energy in forms of chemical bonds for closing the carbon cycle. However, pristine TiO2 possesses a large band gap (3.2 eV), fast recombination of electrons and holes, and low selectivity for the photoreduction of CO2. Recently, considerable progress has been made in the improvement of the performance of TiO2 photocatalysts for CO2 reduction. In this review, we first discuss the fundamentals of and challenges in CO2 photoreduction on TiO2-based catalysts. Next, the recently emerging progress and advances in TiO2 nanostructured and hybrid materials for overcoming the mentioned obstacles to achieve high light-harvesting capability, improved adsorption and activation of CO2, excellent photocatalytic activity, the ability to impede the recombination of electrons-holes pairs, and efficient suppression of hydrogen evolution are discussed. In addition, approaches and strategies for improvements in TiO2-based photocatalysts and their working mechanisms are thoroughly summarized and analyzed. Lastly, the current challenges and prospects of CO2 photocatalytic reactions on TiO2-based catalysts are also presented.

Self-Assembled Few-Layered MoS2 on SnO2 Anode for Enhancing Lithium-Ion Storage.

SnO2 nanoparticles (NPs) have been used as reversible high-capacity anode materials in lithium-ion batteries, with reversible capacities reaching 740 mAh·g-1. However, large SnO2 NPs do not perform well in charge-discharge cycling. In this work, we report the incorporation of MoS2 nanosheet (NS) layers with SnO2 NPs. SnO2 NPs of ~5 nm in diameter synthesized by a facile hydrothermal precipitation method. Meanwhile, MoS2 NSs of a few hundreds of nanometers to a few micrometers in lateral size were produced by top-down chemical exfoliation. The self-assembly of the MoS2 NS layer on the gas-liquid interface was first demonstrated to achieve up to 80% coverage of the SnO2 NP anode surface. The electrochemical properties of the pure SnO2 NPs and MoS2-covered SnO2 NP anodes were investigated. The results showed that the SnO2 electrode with a single-layer MoS2 NS film exhibited better electrochemical performance than the pure SnO2 anode in lithium storage applications.

Recent Progress in Carbon-Based Buffer Layers for Polymer Solar Cells.

Carbon-based materials are promising candidates as charge transport layers in various optoelectronic devices and have been applied to enhance the performance and stability of such devices. In this paper, we provide an overview of the most contemporary strategies that use carbon-based materials including graphene, graphene oxide, carbon nanotubes, carbon quantum dots, and graphitic carbon nitride as buffer layers in polymer solar cells (PSCs). The crucial parameters that regulate the performance of carbon-based buffer layers are highlighted and discussed in detail. Furthermore, the performances of recently developed carbon-based materials as hole and electron transport layers in PSCs compared with those of commercially available hole/electron transport layers are evaluated. Finally, we elaborate on the remaining challenges and future directions for the development of carbon-based buffer layers to achieve high-efficiency and high-stability PSCs.

Silk Fibroin-Based Biomaterials for Biomedical Applications: A Review.

Since it was first discovered, thousands of years ago, silkworm silk has been known to be an abundant biopolymer with a vast range of attractive properties. The utilization of silk fibroin (SF), the main protein of silkworm silk, has not been limited to the textile industry but has been further extended to various high-tech application areas, including biomaterials for drug delivery systems and tissue engineering. The outstanding mechanical properties of SF, including its facile processability, superior biocompatibility, controllable biodegradation, and versatile functionalization have allowed its use for innovative applications. In this review, we describe the structure, composition, general properties, and structure-properties relationship of SF. In addition, the methods used for the fabrication and modification of various materials are briefly addressed. Lastly, recent applications of SF-based materials for small molecule drug delivery, biological drug delivery, gene therapy, wound healing, and bone regeneration are reviewed and our perspectives on future development of these favorable materials are also shared.

Assembly of 6-aza-2-thiothymine on gold nanoparticles for selective and sensitive colorimetric detection of pencycuron in water and food samples.

A facile and novel nanosensor analytical strategy was developed for the colorimetric detection of pencycuron fungicide in rice, potato, cabbage, and water samples based on the pencycuron-induced aggregation of 6-aza-2-thiothymine-functionalized gold nanoparticles (ATT-AuNPs). The ATT-AuNPs exhibited good stability and were characterized with UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectrometry, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential techniques. The addition of pencycuron facilitated strong non-covalent interactions (electrostatic, van der Waals, and H bonding) between pencycuron and ATT-AuNPs, inducing a significant red shift in the surface plasmon resonance (SPR) peak of ATT-AuNPs along with a color change from red to blue. A linear equation was established between absorption ratio (A720/A528) and pencycuron concentration (2.5-100 µM) with a correlation coefficient (R2) of 0.9915. The detection limit was calculated to be 0.42 µM, which was much lower than that of other analytical methods. The designed ATT-AuNP serves as a promising nanosensor for the rapid, simple, and selective label-free colorimetric detection of pencycuron in rice, potato, cabbage, and water samples, is highly sensitive, and does not require sophisticated instruments, tedious sample preparations, and time-consuming separation and pre-concentration procedures.

Morphological evolution of upconversion nanoparticles and their biomedical signal generation.

Advancements in the fabrication of upconversion nanoparticles (UCNPs) for synthetic control can enable a broad range of applications in biomedical systems. Herein, we experimentally verified the role of the hydrothermal reaction (HR) time in the synthesis of NaYF4:20%Yb3+/3%Er3+ UCNPs on their morphological evolution and phase transformation at different temperatures. Characterizations of the as-prepared UCNPs were conducted using X-ray diffraction (XRD), electron microscopy and spectroscopy, and thermogravimetric and upconversion (UC) luminescence analysis. We demonstrated that determining the optimal HR time, also referred to here as the threshold time, can produce particles with good homogeneity, hexagonal phase, and UC luminescence efficiency. Subsequently, the polymer coated UCNPs maintained their original particle size distribution and luminescence properties, and showed improved dispersibility in a variety of solvents, cellular nontoxicity, in vitro bioimaging, and biocompatibility as compared to the bare UCNP. Besides this, polyacrylic acid conjugated UCNPs (UCNP@PAA) also revealed the strong anticancer effect by conjugating with doxorubicin (DOX) as compared to the free DOX. Based on these findings, we suggest that these particles will be useful in drug-delivery systems and as in vivo bioimaging agents synchronously.

Synthesis of fluorescent silicon quantum dots for ultra-rapid and selective sensing of Cr(VI) ion and biomonitoring of cancer cells.

A facile one-step synthetic approach was developed for fabrication of fluorescent silicon quantum dots (Si QDs) and used as a probe for fluorescence detection of hexavalent chromium (Cr (VI)) in environmental water samples. The as-prepared Si QDs exhibit a strong fluorescence emission peak at 520 nm with a quantum yield of 14.2%. The fluorescent Si QDs were rapidly produced by using ascorbic acid as a reductant at 55 °C. The emission peak of Si QDs at 420 nm was effectively quenched upon the addition of Cr(VI). The Si QDs acted as the best fluorescent probe for the detection of Cr(VI) at PBS pH 7.4. The developed probe possessed a good linear correlation (R2 = 0.992) between Cr(VI) concentration (1.25-40 µM) and the (F0-F)/F0 values with a detection limit of 0.65 µM. Furthermore, the Si QDs served as a bio-probe for fluorescence imaging of A549 lung cancer cells and cell viability results confirmed the good biocompatible nature of Si QDs. The as-fabricated Si QDs show several advantages such as rapidity, selectivity and biocompatibility for sensing of Cr(VI) and imaging of A549 cells, which opens a facile analytical platform for environmental and bioimaging applications.

Gold-copper nanoshell dot-blot immunoassay for naked-eye sensitive detection of tuberculosis specific CFP-10 antigen.

Herein, a straightforward and highly specific dot-blot immunoassay was successfully developed for the detection of Mycobacterium tuberculosis antigen (10 kDa culture filtrate protein, CFP-10) via the formation of copper nanoshell on the gold nanoparticles (AuNPs) surface. The principle of dot-blot immunoassay was based on the reduction of Cu2+ ion on the GBP-CFP10G2-AuNPs conjugates, which has gold binding and antigen binding affinities, simultaneously, favouring to appear red dot that can be observed with naked-eye. The dot intensity is proportional to the concentration of tuberculosis antigen CFP-10, which offers a detection limit of 7.6 pg/mL. The analytical performance of GBP-CFP10G2-AuNPs-copper nanoshell dot-blot was superior than that of conventional silver nanoshell. This method was successfully applied to identify the CFP-10 antigen in the clinical urine sample with high sensitivity, specificity, and minimized sample preparation steps. This method exhibits great application potential in the field of nanomedical science for highly reliable point-of-care detection of CFP-10 antigen in real samples to early diagnosis of tuberculosis.