Smartphone-based dual-mode aptasensor with bifunctional metal-organic frameworks as signal probes for ochratoxin A detection

Ochratoxin A (OTA) poses significant risks to human health, being potentially nephrotoxic, carcinogenic, genotoxic, and immuno-toxic. In this work, we developed a dual-mode aptasensor for OTA analysis, integrating colorimetric, electrochemical, and smartphone-based detection. The bifunctional Fe-MIL-88 metal-organic framework, acting as both a nanozyme capable of catalyzing the 3,3',5,5'-tetramethylbenzidine substrate and an electrochemical signal amplifier, enabled OTA quantification through current response or changes in color and absorbance intensity. Besides, the spatial confinement effect enhances the local concentration of Fe-MIL-88 signal probes through rolling circle amplification reaction, thereby contributing to a substantial enhancement in sensitivity. The proposed technique is simple, disposable, highly sensitive and selective, enabling OTA detection in the range of 1 fg/mL to 250 ng/mL, with a limit of detection of 0.22 fg/mL (3σ rule). Furthermore, we successfully detected OTA in corn, wheat, and red wine samples, with results good concordance with those obtained using commercial enzyme-linked immunoassay kits.

Etched CoFe Prussian blue analog nanozymes with superior peroxidase activity for colorimetric biosensing of hydrogen peroxide and dopamine

Nanozymes represent a compelling alternative to natural enzymes due to their exceptional stability and cost-efficiency in diagnostic and therapeutic applications. In this work, a nanozyme etched CoFe Prussian blue analog (etched PBA) was designed and fabricated by a simple approach involving first synthesizing CoFe PBA and then chemical etching. The fabricated etched PBA acts as a peroxidase mimic catalyst. Compared to the naturally occurring enzyme (horseradish peroxidase), the etched PBA exhibited improved peroxidase-like catalytic efficiency for oxidizing 3,3',5,5'-tetramethylbnmenzidine (TMB). Particularly, the exceptional peroxidase-like activity of the etched PBA is attributed to modifications in its electronic and structural properties, which improved affinity for hydrogen peroxide (H2O2) and TMB. Hence, these findings highlight etched PBA as a promising peroxidase mimic, enabling a colorimetric assay for real-time H2O2 and dopamine (DA) detection. H2O2 was detected via PBA-catalyzed TMB oxidation (bluish-green color), while DA monitoring occurred through ox-TMB reduction. The detection thresholds for H2O2 and DA were determined to be 0.083 μM and 0.05 μM, respectively, with broad linear ranges of 0.1 μM - 4.0 mM for H2O2 and 0.1-240 μM for DA. In addition, the etched PBA was validated for real sample analysis, showing potential for enzyme catalysis, biosensing, and colorimetric analysis of pharmaceuticals and biomolecules.

Membranes Based on Aminated Graphene Oxide with High Selectivity Toward Organic Substances

In this work, membranes based on graphene oxide, modified with oleylamine, have been prepared by a simple wet chemistry protocol without the use of complex equipment, elevated temperature, and additional reagents. The membrane material was characterized by a set of physicochemical methods: thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. The prepared membranes are stable in both aqueous and organic media. The membranes have a high flux for organic substances and do not permeate water at room temperature and atmospheric pressure. The selectivity of the membranes toward organic substances increases with their thickness. The highest flux among the tested organic liquids is registered for methanol. The membranes have high selectivity toward ethanol/1-butanol and acetone/1-butanol pairs, which opens up the possibility of separating actual industrial mixtures. The membrane retains 90% of methylene blue from the alcohol solution. Our work expands the possibilities of using modified GO-based membranes in purification and filtration technologies.

Interfacial and Electronic Modulation of M-Bridged Heterostructures with L-Tryptophan and Transition Metallic Oxides: Enhancing Corrosion Resistance and Photocatalytic Activity

Despite remarkable advancements in multilayer composite materials, achieving controlled growth on stationary platforms for optimal corrosion protection and photocatalytic capabilities remains a challenge. In this study, we introduce an innovative approach by integrating bifunctional metal-organic frameworks (MOFs) into plasma-electrolyzed layers made on AZ31 Mg alloy. Metallic oxides of Zr, Ti, and W serve as new pivotal centers for MOF formation, while L-tryptophan (Trp) acts as an organic linker. This innovative approach establishes an efficient electron transport system that acts as a functional pathway for creating highly effective and versatile materials. The tunable structure of the MOF/plasma electrolyzed layer enables it to concurrently display electrochemical stability and photocatalytic activity for the photodegradation of organic pollutants. Remarkably, the WOF complex emerges as a standout performer, effectively shielding the substrate from corrosive anion attacks. This sample showcases exceptional photocatalytic efficiency of 99.61% for crystal violet solution, with sustained performance after five cycles and a 72 h corrosion test (96.55% and 98.39% degradation, respectively). Moreover, DFT calculations elucidate the fundamental bonding modes between MOFs and inorganic constituents, delivering comprehensive insights into their structural formation. Our research addresses the critical challenge of achieving controlled growth for enhanced corrosion resistance and photocatalytic activity, demonstrating a novel pathway for creating multifunctional materials with practical applications across various fields.

Catalytic Design of Matrix-Isolated Ni-Polymer Composites for Methane Catalytic Decomposition

Targeted synthesis of C/composite Ni-based material was carried out by the method of matrix isolation. The composite was formed with regard to the features of the reaction of catalytic decomposition of methane. The morphology and physicochemical properties of these materials have been characterized using a number of methods: elemental analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, temperature programmed reduction (TPR-H₂), specific surface areas (SSA), thermogravimetric analysis, and differential scanning calorimetry (TGA/DSC). It was shown by FTIR spectroscopy that nickel ions are immobilized on the polymer molecule of polyvinyl alcohol, and during heat treatment, polycondensation sites are formed on the surface of the polymer molecule. By the method of Raman spectroscopy, it was shown that already at a temperature of 250 °C, a developed conjugation system with sp2-hybridized carbon atoms begins to form. The SSA method shows that the formation of the composite material resulted in a matrix with a developed specific surface area of 20 to 214 m²/g. The XRD method shows that nanoparticles are essentially characterized by Ni, NiO reflexes. The composite material was established by microscopy methods to be a layered structure with uniformly distributed nickel-containing particles 5-10 nm in size. The XPS method determined that metallic nickel was present on the surface of the material. A high specific activity was found in the process of catalytic decomposition of methane-from 0.9 to 1.4 g_H2/g_cat/h, X_CH4, from 33 to 45% at a reaction temperature of 750 °C without the stage of catalyst preliminary activation. During the reaction, the formation of multi-walled carbon nanotubes occurs.

Enhancement of Release and Solubility of Curcumin from Electrospun PEO-EC-PVP Tripolymer-Based Nanofibers: A Study on the Effect of Hydrogenated Castor Oil

This study reveals the state-of-the-art fabrication of a tripolymer-based electrospun nanofiber (NF) system to enhance the release, solubility, and transdermal penetration of curcumin (Cur) with the aid of in situ release of infused castor oil (Co). In this regard, Cur-loaded Co-infused polyethylene oxide (PEO), ethyl cellulose (EC), and polyvinyl pyrrolidone (PVP) tripolymer-based NF systems were developed to produce a hybridized transdermal skin patch. Weight percentages of 1-4% Cur and 3-10% of Co were blended with PEO-EC-PEO and PEO-EC-PVP polymer systems. The prepared NFs were characterized by SEM, TEM, FT-IR analysis, PXRD, differential scanning calorimetry (DSC), and XPS. Dialysis membranes and vertical Franz diffusion cells were used to study the in vitro drug release and transdermal penetration, respectively. The results indicated that maintaining a Cur concentration of 1-3 wt % with 3 wt % Co in both PEO-EC-Co-Cur@PEO and PEO-EC-Co-Cur@PVP gave rise to nanofibers with lowered diameters (144.83 ± 48.05-209.26 ± 41.80 nm and 190.20 ± 59.42-404.59 ± 45.31 nm). Lowered crystallinity observed from the PXRD patterns and the disappearance of exothermic peaks corresponding to the melting point of Cur suggested the formation of an amorphous NF structure. Furthermore, the XPS data revealed that the Cur loading will possibly take place at the inner interface of PEO-EC-Co-PEO and PEO-EC-Co-PVP NFs rather than on the surface. The beneficiary role of Co on the release and dermal penetration of Cur was further confirmed from the respective release data which indicated that PEO-EC-Co-Cur@PEO would lead to a rapid release (4-5 h), while PEO-EC-Co-Cur@PVP would lead to a sustained release over a period of 24 h in the presence of Co. Transdermal penetration of the released Cur was further evidenced with the development of color in the receiver compartment of the diffusion cell. DPPH results further corroborated that a sustained antioxidant activity is observed in the released Cur where the free-radical scavenging activity is intact even after subjecting to an electrospinning process and under extreme freeze-thaw conditions.

The Oxygen Reduction Activity of Nitrogen-doped Graphene

Graphite nitrogen, pyridine nitrogen and pyrrole nitrogen are the main nitrogen types in nitrogen-doped graphene materials. In order to investigate the mechanism of the oxygen reduction activity of nitrogen-doped graphene, several models of nitrogen-doped graphene with different nitrogen contents and different nitrogen types are developed. The nitrogen content is varied from 1.3 at% to 7.8 at%, and the adsorption energy is calculated according to the established models, then the band gaps are analyzed through the optimization results, so as to compare the magnitude of the conductivity. Finally, the oxygen reduction activity of graphite nitrogen-doped graphene (GNG) is found to be better than pyridine nitrogen-doped graphene (PDNG) and pyrrole nitrogen-doped graphene (PLNG) when the nitrogen content is lower than 2.6 at%, and the oxygen reduction activity of PDNG is the best when the nitrogen content was higher than 2.6 at%.

Hierarchical Graphitic Carbon-Encapsulating Cobalt Nanoparticles for Catalytic Hydrogenation of 2,4-Dinitrophenol

Cobalt hierarchical graphitic carbon nanoparticles (Co@HGC) (1), (2), and (3) were prepared by simple pyrolysis of a cobalt phenanthroline complex in the presence of anthracene at different temperatures and heating times, under a nitrogen atmosphere. The samples were used for the catalytic hydrogenation of 2,4-dinitrophenol. Samples (1) and (3) were prepared by heating at 600 °C and 800 °C respectively, while (2) was prepared by heating at 600 °C with an additional intermediate stage at 300 °C. This work revealed that graphitization was catalyzed by cobalt nanoparticles and occurred readily at temperatures of 600 °C and above. The nanocatalysts were characterized by Scanning Electron Microscopy SEM, energy dispersive X-ray analysis EDX, Raman, Xrd, and XPS. The analysis revealed the presence of cobalt and cobalt oxide species as well as graphitized carbon, while TEM analysis indicated that the nanocatalyst contains mainly cobalt nanoparticles of 3–20 nm in size embedded in a lighter graphitic web. Some bamboo-like multiwall carbon nanotubes and graphitic onion-like nanostructures were observed in (3). The structures and chemical properties of the three catalysts were correlated with their catalytic activities. The apparent rate constants kapp (min−1) of the 2,4-dinitrophenol reductions were 0.34 for (2), 0.17 for (3), 0.04 for (1), 0.005 (no catalyst). Among the three studied catalysts, the highest rate constant was obtained for (2), while the highest conversion yield was achieved by (3). Our data show that an increase in agglomeration of the cobalt species reduces the catalytic activity, while an increase in pyrolysis temperature improves the conversion yield. The nanocatalyst enhances hydrogen generation in the presence of sodium borohydride and reduces 2,4-dinitrophenol to p-diamino phenol. The best nanocatalyst (3) was prepared at 800 °C. It consisted of uniformly distributed cobalt nanoparticles sheltered by hierarchical graphitic carbon. The nanocatalyst is easily separated and recycled from the reaction system and proved to be degradation resistant, to have robust stability, and high activity towards the reduction reaction of nitrophenols.

Carbon nanomaterials treated by combination of oxidation and flash for highly efficient solar water evaporation

The high-efficiency solar evaporation is a potential technique to desalinate hypersaline wastewater and seawater to alleviate the global fresh water shortage. Photo-thermal agent and solar evaporator with low-cost raw materials, high photo-thermal conversion efficiency and simple-fast preparation methods is crucial to realize the industrial application of solar evaporation. Herein, carbon nanomaterial with higher light absorption and photo-thermal conversion efficiency than that of carbon black was obtained by combination treatment of carbon black with oxidation and flash illumination. In order to characterize the evaporation performance of the devices, a floating evaporator was fabricated with the carbon nanomaterial on the top of polyethylene foam wrapped with non-woven fabrics. The evaporation rate and photo-thermal conversion efficiency of evaporators were affected significantly by environmental temperature and humidity. At the environmental temperature of 19.5 °C, the evaporator fabricated with the combined treated carbon nanomaterial as photo-thermal agents presents a stable evaporation rate at 1.27 kg m^-2 h^-1 and solar evaporation efficiency at 78.7% under 1 kW m^-2 simulated sun illumination, which are higher than those of evaporator with carbon black (1.13 kg m^-2 h^-1 and 68.1%). The distilled water obtained from the solar evaporator met the standards of drinkable water. Overall, the experimental result demonstrates a great promise application of treated carbon nanomaterial as a photo-thermal agent in the field of seawater desalination and solar-energy collector.

Studies on Kinetics, Isotherms, Thermodynamics and Adsorption Mechanism of Methylene Blue by N and S Co-Doped Porous Carbon Spheres

Heteroatom-doped carbon is widely used in the fields of adsorbents, electrode materials and catalysts due to its excellent physicochemical properties. N and S co-doped porous carbon spheres (N,S-PCSs) were synthesized using glucose and L-cysteine as carbon and heteroatom sources using a combined hydrothermal and KOH activation process. The physicochemical structures and single-factor methylene blue (MB) adsorption properties of the N,S-PCSs were then studied. The optimized N,S-PCSs-1 possessed a perfect spherical morphology with a 2-8-μm diameter and a large specific area of 1769.41 m2 g-1, in which the N and S contents were 2.97 at% and 0.88 at%, respectively. In the single-factor adsorption experiment for MB, the MB adsorption rate increased with an increase in carbon dosage and MB initial concentration, and the adsorption reached equilibrium within 2-3 h. The pseudo-second-order kinetic model could excellently fit the experimental data with a high R2 (0.9999). The Langmuir isothermal adsorption equation fitted well with the experimental results with an R2 value of 0.9618, and the MB maximum adsorption quantity was 909.10 mg g-1. The adsorption of MB by N,S-PCSs-1 was a spontaneous, endothermic, and random process based on the thermodynamics analyses. The adsorption mechanism mainly involved Van der Waals force adsorption, π-π stacking, hydrogen bonds and Lewis acid-base interactions.

Enhancing As(V) and As(III) adsorption performance of low alumina fly ash with ferric citrate modification: Role of FeSiO3 and monosodium citrate

Fly ash and arsenic species have been regarded as contaminants that pollute the environment. Herein, low alumina fly ash (LAFA) was utilized to fabricate the As(V) and As(III) adsorbent via combining the routes of alkali fusion and incipient-wetness impregnation. The characterization results suggested that the grafted ferric citrate was coordinated to LAFA by substituting a Si⁴⁺ to a Fe³⁺, and the compound monosodium citrate was observed. Based on the XPS analysis, the C-O and -COO^- groups of monosodium citrate played the significant role in uptaking As(V) and As(III) species by chemical complexation, the FeOOH adsorbed As(V) and As(III) species via ion-exchange, and the Fe₂O₃ oxidize As(III) into As(V). Additionally, it was observed that the As(V) removal performance by adsorbent prepared with different modifiers was in the order of FeC₆H₅O₇ (ca. 93.7%) > C₆H₈O₇ (84%) > HCl (73%). And then, the optimal adsorbent synthesis condition for As(V) uptake was explored at ferric citrate loaded LAFA with 1:1 mass ratio (fly ash to NaOH) under temperature 923 K. The maximum monolayer adsorption capacities of the optimal adsorbent were 2725.0 μgAs(V)/g and 2281.9 μgAs(III)/g, and the removal efficiency of As(V) and As(III) was near 100% for their initial concentrations below 500 ppb, where the residual arsenic concentration met the required standard in drinking water (lower than 10 ppb).

Aggregation-induced negative differential resistance in graphene oxide quantum dots

Negative differential resistance (NDR) devices have attracted considerable interest due to their potential applications in switches, memory devices, and analog-to-digital converters. Modulation of the NDR is an essential issue for the development of NDR-based devices. In this study, we successfully synthesized graphene oxide quantum dots (GOQDs) using graphene oxide, cysteine, and H2O2. The current-voltage characteristics of the GOQDs exhibit a clear NDR in the ambient environment at room temperature. A peak-to-valley ratio as high as 4.7 has been achieved under an applied voltage sweep from -6 to 6 V. The behavior of the NDR and its corresponding peak-to-valley ratio can be controlled by adjusting the range of applied voltages, air pressure, and relative humidity. Also, the NDR is sensitive to the the concentration of H2O2 added in the synthesis. The charge carrier injection through the trapping states, induced by the GOQD aggregation, could be responsible for the NDR behavior in GOQDs.

Guiding Principles for Designing Highly Efficient Metal-Free Carbon Catalysts

Carbon nanomaterials are promising metal-free catalysts for energy conversion and storage, but the catalysts are usually developed via traditional trial-and-error methods. To rationally design and accelerate the search for the highly efficient catalysts, it is necessary to establish design principles for the carbon-based catalysts. Here, theoretical analysis and material design of metal-free carbon nanomaterials as efficient photo-/electrocatalysts to facilitate the critical chemical reactions in clean and sustainable energy technologies are reviewed. These reactions include the oxygen reduction reaction in fuel cells, the oxygen evolution reaction in metal-air batteries, the iodine reduction reaction in dye-sensitized solar cells, the hydrogen evolution reaction in water splitting, and the carbon dioxide reduction in artificial photosynthesis. Basic catalytic principles, computationally guided design approaches and intrinsic descriptors, catalytic material design strategies, and future directions are discussed for the rational design and synthesis of highly efficient carbon-based catalysts for clean energy technologies.

Edge-Functionalized Graphene Nanoplatelets as Metal-Free Electrocatalysts for Dye-Sensitized Solar Cells

A scalable and low-cost production of graphene nanoplatelets (GnPs) is one of the most important challenges for their commercialization. A simple mechanochemical reaction has been developed and applied to prepare various edge-functionalized GnPs (EFGnPs). EFGnPs can be produced in a simple and ecofriendly manner by ball milling of graphite with target substances (X = nonmetals, halogens, semimetals, or metalloids). The unique feature of this method is its use of kinetic energy, which can generate active carbon species by unzipping of graphitic CC bonds in dry conditions (no solvent). The active carbon species efficiently pick up X substance(s), leading to the formation of graphitic CX bonds along the broken edges and the delamination of graphitic layers into EFGnPs. Unlike graphene oxide (GO) and reduced GO (rGO), the preparation of EFGnPs does not involve toxic chemicals, such as corrosive acids and toxic reducing agents. Furthermore, the prepared EFGnPs preserve high crystallinity in the basal area due to their edge-selective functionalization. Considering the available edge X groups that can be selectively employed, the potential applications of EFGnPs are unlimited. In this context, the synthesis, characterizations, and applications of EFGnPs, specifically, as metal-free carbon-based electrocatalysts for dye-sensitized solar cells (DSSCs) in both cobalt and iodine electrolytes are reviewed.

Cobalt/Molybdenum Phosphide and Oxide Heterostructures Encapsulated in N-Doped Carbon Nanocomposite for Overall Water Splitting in Alkaline Media

The development of designing and searching inexpensive electrocatalysts with high activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant to enable water splitting as a future renewable energy source. Herein, we synthesize a new CoP(MoP)-CoMoO₃ heterostructure coated by a N-doped carbon shell [CoP(MoP)-CoMoO₃@CN] via thermal decomposition and phosphatizing of the CoMoO₄·0.9H₂O nanowires encapsulated in N-doped carbon. At 10 mA·cm^-2, this CoP(MoP)-CoMoO₃@CN nanocomposite exhibits superior electrocatalytic activity at low overpotentials of 296 mV for OER and 198 mV for HER in alkaline media. More importantly, we achieve a current density of 10 mA·cm^-2 at 1.55 V by using this CoP(MoP)-CoMoO₃@CN as both cathode and anode for overall water splitting. This promising performance could be due to the high activity of CoP(MoP)-CoMoO₃ and the good conductivity of the external mesoporous N-carbon shell, which makes the CoP(MoP)-CoMoO₃@CN nanowires a competitive alternative to noble-metal-based catalysts for water splitting.

Facile fabrication of Cu-based alloy nanoparticles encapsulated within hollow octahedral N-doped porous carbon for selective oxidation of hydrocarbons

HKUST-1 serves as a template for an imidazolium-based ionic polymer; anion exchange and subsequent topotactic transformation generate hollow nitrogen-doped porous carbon incorporated with Cu-based alloy nanoparticles.

Hollow carbon materials with versatile chemical compositions and complicated shell architectures hold great promise in heterogeneous catalysis. However, it is a daunting challenge to synthesize metal alloy nanoparticles (NPs) supported by hollow nanostructures. Herein, we present a simple approach for facile fabrication of Pd–Cu alloy NPs embedded in hollow octahedral N-doped porous carbon (Pd–Cu@HO-NPC). The hollow material is derived from HKUST-1 coated by an imidazolium-based ionic polymer (ImIP). Water-sensitive HKUST-1 is simultaneously removed in the process of anion exchange between bromide in the ImIP shell and tetrachloropalladate in aqueous medium. The released Cu(ii) ions and exchanged Pd(ii) ions serve as Cu and Pd sources in the subsequent pyrolysis. The resultant Pd–Cu@HO-NPC exhibits high catalytic activity, selectivity, stability and recyclability in the aerobic oxidation of hydrocarbons. More attractively, the synthetic strategy is of excellent generality, and could be extended to the synthesis of Cu-based bimetallic and trimetallic alloy NPs, such as Pt–Cu@HO-NPC and Pd–Pt–Cu@HO-NPC. This work highlights the superiority of water-sensitive metal–organic frameworks in the ingenious design of hollow carbon materials incorporated with well-dispersed metal alloy NPs.

Highly Dispersive MoP Nanoparticles Anchored on Reduced Graphene Oxide Nanosheets for an Efficient Hydrogen Evolution Reaction Electrocatalyst

Electrochemical water-splitting with non-noble metal catalysts provides an eco-friendly strategy for renewable production of hydrogen. In this study, the MoP@C@reduced graphene oxide (rGO) composite was prepared via mild reactions through a chemical bath and postannealing process. With the assistance of citric acid, the MoP@C@rGO composite containing ultrafine MoP nanoparticles with a size of 3 nm anchored on two-dimensional C/rGO nanosheets has been obtained. The chelation effect with citric acid and the merits of rGO not only lead to affordable active sites but also improved the electrical conductivity and stability at the same time. Serving as the hydrogen evolution reaction (HER) electrocatalyst, the MoP@C@rGO composite presents a small overpotential of 168.9 mV at 10 mA cm^-2. It has superior durability when compared to samples of pure MoP, MoP@C, and MoP@rGO. The relative high activity and stable performance as well as the simple preparation process make the MoP@C@rGO composite a promising HER electrocatalyst.

Pyridinic-nitrogen highly doped nanotubular carbon arrays grown on a carbon cloth for high-performance and flexible supercapacitors

Pyridinic-nitrogen highly doped nanotubular carbon (NTC) arrays with multimodal pores in the wall were synthesized via a one-step template strategy using 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as both carbon and nitrogen precursors and ZnO nanowire (ZnO NW) arrays grown on carbon clothes as templates for high-performance supercapacitors (SCs). A strikingly high N-doping level of 14.3% and pyridine N (N-6) dominance as high as 69.1% of the total N content were achieved. Both the N content and N configuration can be well tailored by adjusting the carbonization temperatures of TATB. When directly applied as flexible SCs, the N-doped NTC yields a high specific capacitance of 310.7 F g^-1 (0.8 A g^-1), a cycling retention ratio of 105.1% after 20 000 charge-discharge cycles, and excellent capacitance retention rates of 93.6%, 74.2%, and 53.6% at 8 A g^-1, 40 A g^-1, and 80 A g^-1, respectively, as compared to the value at 0.8 g^-1. TATB, as the only precursor of C and N, is expected to be of great significance for the further design and synthesis of N-doped sp² carbon nanostructures with selective N configurations and controlled N content.

Coaxial heterojunction carbon nanofibers with charge transport and electrocatalytic reduction phases for high performance dye-sensitized solar cells

Coaxial CNFs featured high conductivity derived from HP, and high N content and defective sites derived from PAN.

General Strategy for the Synthesis of Transition-Metal Phosphide/N-Doped Carbon Frameworks for Hydrogen and Oxygen Evolution

Transition metal phosphides (TMPs) have been identified as promising nonprecious metal electrocatalyst for hydrogen evolution reaction (HER) and other energy conversion reactions. Herein, we reported a general strategy for synthesis of a series of TMPs (Fe₂P, FeP, Co₂P, CoP, Ni₂P, and Ni₁₂P₅) nanoparticles (NPs) with different metal phases embedded in a N-doped carbon (NC) matrix using metal salt, ammonium dihydrogen phosphate, and melamine as precursor with varying molar ratios and thermolysis temperatures. The resultant TMPs can serve as highly active and durable bifunctional electrocatalyst toward HER and oxygen evolution reaction (OER). In particular, the Ni₂P@NC phase only requires an overpotential of ∼138 mV to derive HER in 0.5 M H₂SO_4, and ∼320 mV for OER in 1.0 M KOH at the current density of 10 mA cm^-2. Because of the encapsulation of NC that can effectively prevent corrosion of embedded TMP NPs, Ni₂P@NC exhibits almost unfading catalytic performance even after 10 h under both acidic and alkaline solutions. This synthesis strategy provides a new avenue to exploring TMPs as highly active and stable electrocatalyst for the HER, OER, and other electrochemical applications.

Interfacial engineering of renewable metal organic framework derived honeycomb-like nanoporous aluminum hydroxide with tunable porosity

Novel honeycomb-like mesoporous aluminum hydroxide (pATH) was synthesized via a facile one-step reaction by employing ZIF-8 as a template.

Novel honeycomb-like mesoporous aluminum hydroxide (pATH) was synthesized via a facile one-step reaction by employing ZIF-8 as a template. This self-decomposing template was removed automatically under acidic conditions without the need for any tedious or hazardous procedures. Meanwhile, the pore size of pATH was easily modulated by tuning the dimensions of the ZIF-8 polyhedrons. Of paramount importance was the fact that the dissolved ZIF-8 in solution was regenerated upon deprotonation of the ligand under mild alkali conditions, and was reused in the preparation of pATH, thus forming a delicate synthesis cycle. The renewable template conferred cost-effective and sustainable features to the as-synthesized product. As a proof-of-concept application, the fascinating nanoporous structure enabled pATH to load more phosphorous-containing flame retardant and endowed better interaction with epoxy resin over that of commercial aluminum hydroxide. The limiting oxygen index, UL-94 vertical burning test and cone calorimeter test showed that the results of epoxy with the modified pATH rivalled those of epoxy with two times the loading amount of the commercial counterpart, while the former presented better mechanical properties. The proposed “amorphous replica method” used in this work will advance the potential for launching a vast area of research and technology development for the preparation of porous metal hydroxides for use in practical applications.

Microwave assisted synthesis of MoS2/nitrogen-doped carbon shell–core microspheres for Pt-free dye-sensitized solar cells

Novel MoS₂/nitrogen-doped carbon shell–core microsphere counter electrodes of dye-sensitized solar cells with a high efficiency of 6.2%.

Fabrication of Nitrogen-Doped Hollow Mesoporous Spherical Carbon Capsules for Supercapacitors

A novel "dissolution-capture" method for the fabrication of nitrogen-doped hollow mesoporous spherical carbon capsules (N-HMSCCs) with high capability for supercapacitor is developed. The fabrication process is performed by depositing mesoporous silica on the surface of the polyacrylonitrile nanospheres, followed by a dissolution-capture process occurring in the polyacrylonitrile core and silica shell. The polyacrylonitrile core is dissolved by dimethylformamide treatment to form a hollow cavity. Then, the polyacrylonitrile is captured into the mesochannel of silica. After carbonization and etching of silica, N-HMSCCs with uniform mesopore size are produced. The N-HMSCCs show a high specific capacitance of 206.0 F g(-1) at a current density of 1 A g(-1) in 6.0 M KOH due to its unique hollow nanostructure, high surface area, and nitrogen content. In addition, 92.3% of the capacitance of N-HMSCCs still remains after 3000 cycles at 5 A g(-1). The "dissolution-capture" method should give a useful enlightenment for the design of electrode materials for supercapacitor.

A three-dimensional porous MoP@C hybrid as a high-capacity, long-cycle life anode material for lithium-ion batteries

Metal phosphides are great promising anode materials for lithium-ion batteries with a high gravimetric capacity. However, significant challenges such as low capacity, fast capacity fading and poor cycle stability must be addressed for their practical applications. Herein, we demonstrate a versatile strategy for the synthesis of a novel three-dimensional porous molybdenum phosphide@carbon hybrid (3D porous MoP@C hybrid) by a template sol-gel method followed by an annealing treatment. The resultant hybrid exhibits a 3D interconnected ordered porous structure with a relatively high surface area. Benefiting from its advantages of microstructure and composition, the 3D porous MoP@C hybrid displays excellent lithium storage performance as an anode material for lithium-ion batteries in terms of specific capacity, cycling stability and long-cycle life. It presents stable cycling performance with a high reversible capacity up to 1028 mA h g(-1) at a current density of 100 mA g(-1) after 100 cycles. By ex situ XRD, HRTEM, SAED and XPS analyses, the 3D porous MoP@C hybrid was found to follow the Li-intercalation reaction mechanism (MoP + xLi(+) + e(-)↔ LixMoP), which was further confirmed by ab initio calculations based on density functional theory.

Layer-by-Layer Self-Assembled Graphene Multilayers as Pt-Free Alternative Counter Electrodes in Dye-Sensitized Solar Cells

Low cost, charged, and large scale graphene multilayers fabricated from nitrogen-doped reduced graphene oxide N-rGO(+), nitrogen and sulfur codoped reduced graphene oxide NS-rGO(+), and undoped reduced graphene oxide rGO(-) were applied as alternative counter electrodes in dye-sensitized solar cells (DSSCs). The neat rGO-based counter electrodes were developed via two types of layer-by-layer (LBL) self-assembly (SA) methods: spin coating and spray coating methods. In the spin coating method, two sets of multilayer films were fabricated on poly(diallyldimethylammonium chloride) (PDDA)-coated fluorine-doped tin oxide (FTO) substrates using GO(-) combined with N-GO(+) followed by annealing and denoted as [rGO(-)/N-rGO(+)]n or with NS-GO(+) and denoted as [rGO(-)/NS-rGO(+)]n for counter electrodes in DSSCs. The DSSCs employing new types of counter electrodes exhibited ∼7.0% and ∼6.2% power conversion efficiency (PCE) based on ten bilayers of [rGO(-)/N-rGO(+)]10 and [rGO(-)/NS-rGO(+)]10, respectively. The DSSCs equipped with a blend of one bilayer of [rGO(-):N-rGO(+)] and [rGO(-):NS-rGO(+)] on PDDA-coated FTO substrates were prepared from a spray coating and showed ∼6.4% and ∼5.6% PCE, respectively. Thus, it was demonstrated that a combination of undoped, nitrogen-doped, and nitrogen and sulfur codoped reduced graphene oxides can be considered as potentially powerful Pt-free electrocatalysts and alternative electrodes in conventional photovoltaic devices.

Controllable synthesis of nitrogen-doped hollow carbon nanospheres with dopamine as precursor for CO2 capture

Nitrogen-doped hollow carbon nanospheres are synthesized by using dopamine as carbon and nitrogen sources and tetraethyl orthosilicate as structure-assistant agent.

Porous hollow manganites with robust composite shells for oxidation of CO at low temperature

Hollow-type manganite-coated silica microspheres were synthesized via the thermal hydrolysis of urea. The Mn₂O₃/SiO₂_3T microspheres with robust shells exhibit best catalytic performance for CO oxidation even at temperatures below 200 °C.

Nitrogen-doped carbon microspheres counter electrodes for dye-sensitized solar cells by microwave assisted method

Nitrogen-doped carbon microspheres were synthesized for counter electrodes of dye-sensitized solar cells with a high efficiency of 6.28%.

Hollow Nanostructured Metal Silicates with Tunable Properties for Lithium Ion Battery Anodes

Hollow nanostructured materials have attracted considerable interest as lithium ion battery electrodes because of their good electrochemical properties. In this study, we developed a general procedure for the synthesis of hollow nanostructured metal silicates via a hydrothermal process using silica nanoparticles as templates. The morphology and composition of hollow nanostructured metal silicates could be controlled by changing the metal precursor. The as-prepared hierarchical hollow nanostructures with diameters of ∼100-200 nm were composed of variously shaped primary particles such as hollow nanospheres, solid nanoparticles, and thin nanosheets. Furthermore, different primary nanoparticles could be combined to form hybrid hierarchical hollow nanostructures. When hollow nanostructured metal silicates were applied as anode materials for lithium ion batteries, all samples exhibited good cyclic stability during 300 cycles, as well as tunable electrochemical properties.

One-pot fabrication of hollow cross-linked fluorescent carbon nitride nanoparticles and their application in the detection of mercuric ions

Hollow cross-linked fluorescent carbon nitride nanoparticles (CNNPs) were fabricated via a facile one-pot solvothermal process. The obtained CNNPs were characterized by multiple analytical techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The excitation-dependent fluorescence emission spectra showed significant differences for the CNNPs derived from various proportions of citric acid monohydrate and urea. The fluorescence quantum yield of the obtained CNNPs could reach 31%. The CNNPs exhibited good fluorescence quenching selectivity to mercuric ions. Concentration experiments showed that there existed two parts of linear relationship between fluorescence intensity and concentration of Hg(2+) ions in the range of 0.1-8 and 8-32 μM. The limit of detection (LOD) was estimated to be 0.094 μM. This method can be applied to the detection of Hg(2+) ions in tap water samples.

Hydrothermal synthesis of nitrogen doped graphene nanosheets from carbon nanosheets with enhanced electrocatalytic properties

Nitrogen doped graphene nanosheets (NGS) were synthesized from carbon nanosheets (CNS). The as-synthesized NGS were employed to selectively detect dopamine (DA) and uric acid (UA) with enhanced electrocatalytic activity.

Transition metal selenides as efficient counter-electrode materials for dye-sensitized solar cells

We synthesized three targeted TMSs and used them as CEs in high efficiency DSCs. These selenides had excellent catalytic activity for the reduction of triiodine except for MoSe₂. Theoretical investigation revealed that the unsatisfactory performance of MoSe₂ mainly originated from the processes of adsorption and charge-transfer. These results may pave the way for reasonable selection of catalyst in the field of electrocatalysis.

Multi-shelled hollow micro-/nanostructures

Recent advances in multi-shelled hollow micro-/nanostructures were reviewed, and the correlation between their geometric properties and specific performance was highlighted.

Graphene nanoplatelets doped with N at its edges as metal-free cathodes for organic dye-sensitized solar cells

Challenging precious Pt-based electrocatalysts for dye-sensitized solar cells (DSSCs), graphene nanoplatelets that are N-doped at the edges (NGnPs) are prepared via simply ball-milling graphite in the presence of nitrogen gas. DSSCs based on specific nanoplatelets designated "NGnP5" display superior photovoltaic performance (power conversion efficiency, 10.27%) compared to that of conventional Pt-based devices (9.96%). More importantly, the NGnP counter electrode exhibits outstanding electrochemical stability and electrocatalytic activity with a cobalt-complex redox couple.

Au-TiO(2) nanoscale heterodimers synthesis from an ambient spark discharge for efficient photocatalytic and photothermal activity

Ultrafine Au particles incorporating TiO2 heterodimers were synthesized using an ambient heterogeneous spark discharge and the resultant materials were employed both in oxidizing photocatalytically CO gas and killing photothermally cancerous cells. Ti-Au spark configuration was employed to vaporize Ti and Au components into an airflow and finally ultrafine Au particles (∼2 nm in lateral dimension) were incorporated with TiO2 nanoparticles in the form of Au-TiO2 heterodimers (∼38 nm in lateral dimension) with enhanced photocatalytic (in CO oxidation) and photothermal activity (in cancerous cell killing) under visible light. We propose that the localized surface plasmon resonance of ultrafine Au particles on TiO2 supports, induced by the visible light, would promote the adsorption-oxidation of CO and photothermal killing of HeLa cells. The present strategy may be suitable to fabricate other Au-metal oxide nanocomposites for catalytic and biomedical applications.