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The utilization of solar energy and valid photocatalyst is one of the most effective strategies to achieve water splitting into hydrogen (H2) and oxygen (O2). Although enormous effort has been devoted to photocatalysts, the sunlight still cannot be fully utilized by the developed photocatalysts. It is important but remains challenging to develop a broad spectrum-driven photocatalyst for overall water splitting. Here, we design a UV-Vis-NIR broad spectrum-driven carbon dots modified WO2-NaxWO3 (WO2-NaxWO3-CDs) composite as photocatalyst for overall water splitting without requirement of any sacrificial agents or cocatalysts. When the concentration of CDs in the sample is 0.008 gCDs/gcatalyst, the WO2-NaxWO3-CDs shows the highest photocatalytic activity with stoichiometric ratio of H2/O2 evolutions and their rates are 0.05/0.02, 2.58/1.24, 4.74/2.28 μmol/h under UV (λ 760 nm) light irradiation, respectively. It is also impressive that the photocatalyst shows excellent stability for about 6 cycles of repetitive experiments. The WO2-NaxWO3-CDs composites functioned as broad spectrum-driven photocatalyst for overall water splitting should attribute to the synergistic effect of WO2-NaxWO3 and CDs, in which the WO2-NaxWO3 provides the suitable bandgap, while the CDs can enhance light absorption and accelerate separation efficiencies of photo-generated charge carriers.

In this paper, a notable chitosan/poly(ethylene oxide) nanofiber mats containing tea tree oil liposomes (TOL-CENs) were successfully fabricated using electrospinning process. The microstructures and morphology were characterized by scanning electron microscopy. The porosity, fluid absorbability, water vapor permeability and mechanical properties of nanofiber mats were also estimated by ethanol density method, gravimetric method, dish method and tensile test, respectively. Compared to the chitosan/poly(ethylene oxide) composite freeze-dried sponges containing tea tree oil liposomes, TOL-CENs had greater porosity, water absorption, breathability and better mechanical properties. In addition, the controlled-release properties and long-term bactericidal capability of the material were also assessed. From the analysis of the release kinetics and mechanism, it was found that the significant decreased terpinen-4-ol concentration gradient from liposomal surface to the outside of material was the key to the sustained terpinen-4-ol release in virtue of liposomal encapsulation. TOL-CENs exhibited long-term and more excellent microbicidal effects against Staphylococcus aureus, Escherichia coli and Candida albicans than chitosan/poly(ethylene oxide) nanofiber mats. The combination of tea tree oil liposomes and chitosan in nanofiber mats synergistically destroyed cell membrane, prevented cell adhesion and caused the irregular aggregation of cytoplasm, resulting in cell disintegration observed by transmission electron microscope. In summary, TOL-CENs had potential application value as a long-term antimicrobial nonwoven materials.

Electret filters are widely used in particulate matter filtration due to their filtration efficiency that can be greatly improved by electrostatic forces without sacrificing the air resistance. However, the attenuation of the filtration efficiency remains a challenge. In this study, we report a novel strategy for producing an electret melt blown filter with superior filtration efficiency stability through a thermally stimulated charging method. The proposed approach optimizes the crystal structure and therefore results in the increased production probability of the charge traps. In addition, the re-trapping phenomenon caused by the thermal stimulation during the charging process can greatly increase the proportion of deep charge to shallow charge and improve the charge stability. A superior electret melt blown filtration material with a high filtration efficiency of 99.65%, low pressure drop of 120 Pa, and satisfactory filtration efficiency stability was produced after three cyclic charging times. The excellent filtration performance indicated that the developed material is a good air filtration candidate component for personal protection applications.

In this study, the performance of an evaporative cooling unit device based on the M-cycle cooling principles is evaluated experimentally. Numerical models of the experimental prototype and its scale model have been developed by using CFD software. Numerical analysis of a multi-unit evaporative cooling device in series has been carried out. The cooling effect of multistage series and multistage iteration is also studied. Experimental result shows that under low relative humidity, the decrease in air temperature along the channel is greater than that under a higher relative humidity. The predicted outlet temperature of the dry and wet channels by the experimental-sized model agrees well with the experimental results. The effect of different air volumes in each stage on the cooling (wet-bulb and dew-point) effectiveness is discussed. It’s found that under the same air volume at each stage, the smaller-sized model can achieve 18.3% higher cooling effectiveness compared with the experimental-sized model. The wet-bulb effectiveness of the smaller-sized model with halved flow rate of each stage could achieve as high as 117%. Furthermore, the first stage among four-stage evaporative cooling model has the highest cooling effectiveness.

Photocatalytic hydrogen production on semiconductors has been intensively researched in the past years, yet it still lacks research on efficient and stable photocatalysis in seawater. In this paper, with cadmium sulfide (CdS) as a sample photocatalyst and carbon dots (CDs) as cocatalyst, we fabricated a series of CDs/CdS composites serving as efficient hydrogen production photocatalysts in both water and seawater. In this case, the optimal CDs/CdS-S composites (nanosheet with cocatalyst content of 0.01 gCDs/gcatalyst) exhibit prominent H2 production rate of 4.64 mmol h−1 g−1 (6.70 mmol h−1 g−1, water) and AQE of 11.8% (19.3%, water) under 420 nm light irradiation in seawater, which are about 265 and 169 (78 and 77, water) times of those of the non-modified irregular CdS in seawater, respectively. The excellent activity and stability are attributed to the competency of CDs that not only dramatically improves the charge separation efficiency, but also plays indispensable role in resisting the distraction from various ionic components in seawater. We hope our work can provide a feasible perspective for constructing high-efficient photocatalyst towards practical applications.

Solar light driven photocatalytic water splitting to produce hydrogen (H2) and oxygen (O2) on large scale is a promising solution to acquire the clean and sustainable energy sources. Enlightened by mimicking natural Z-scheme photosynthesis, the artificial visible light-driven water splitting photocatalyst of NiO/carbon dots/BiVO4 (NiO/CDs/BiVO4) composite was constructed. The designed NiO/CDs/BiVO4 as all-solid-state Z-scheme photocatalyst exhibits efficient photocatalyatic activity for overall water splitting without any cocatalysts or scavengers. In the Z-scheme system, the NiO and BiVO4 can respectively act as H2 evolution and O2 evolution photocatalysts, while the CDs can serve as solid electron mediator. The optimal NiO/CDs/BiVO4 photocatalyst shows the H2 and O2 production rates of 1.21 and 0.60 μmol·h−1, respectively, with the CDs concentration in the composite of 5 wt% and the mass ratio of NiO to BiVO4 of 3. The incorporation of CDs employed as the solid-state electron mediator boosts the effective electron transfer and charges separation, resulting in the improved photocatalytic activity of the designed Z-scheme system.

Electrochemical reduction of carbon dioxide (CO2RR) to useful chemicals and fuels is one of the promising methods to reduce the accumulated greenhouse gas in the atmosphere and simultaneously satisfy sustainable energy demands. Metallic Ag has been reported in numerous studies for its excellent properties in CO2 reduction. However, most Ag catalysts require a large overpotential to realize high selectivity and the Faradaic efficiency (FE) is relatively low. Moreover, the synthetic methods of efficient Ag catalysts are usually complicated and time-consuming. In this work, a phosphate silver-derived silver (PD-Ag) electrocatalyst was fabricated by a quick facile electroreduction method, showing superior performance for the selective reduction of CO2 to CO. The maximum FE of PD-Ag could reach 97.3% with a potential of −0.7 V vs RHE, and a current density of 2.93 mA cm–2. It is demonstrated that a 19-fold increase of the electrochemically active surface area (ECSA) is obtained for PD-Ag compared to polycrysta...

Multifunctional carbon dots (CDs) with lifetime thermal sensing, nucleolus imaging, and antialgal activity properties were synthesized directly from ascorbic acid aqueous solution by a one-step electrochemical method at room temperature. The as-prepared CDs are responsive to temperature and exhibit an accurate linear response of fluorescence intensity vs. temperature (20-100 °C). These CDs can enter a cell and nucleolus, adsorb on the nucleic acids (DNA and RNA) and the fluorescence intensity of CDs is increased by the adsorption of nucleic acids. In addition, the CDs can inhibit the activity of RuBisCO in Anabaena sp., leading to reducing the growth of Anabaena sp. All these properties make the CDs serve as effective fluorescence-based nanothermometers, nucleolus probes, and antialgal agents.

Polyaniline-encapsulated carbon/copper composite nanofibers (PANI/CuCNFs) were synthesized by a facile and efficient method combining electrospinning and in-situ polymerization, which were further applied to the laccase (Lac) based biosensor for polyphenol pollutant detection. The morphology and composition of the fabricated nanocomposite were investigated by a series of advanced characterization techniques. The electrochemical behaviour of the novel biosensor was studied through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. Results showed that the addition of PANI/CuCNFs apparently improved the electrocatalytic properties of the Lac-based biosensor towards hydroquinone. The constructed biosensor possessed a high sensitivity (41.65 μA mM−1), a low detection limit (0.24 μM), and a wide linear range from 500 nM to 110 μM, as well as satisfied selectivity, reproducibility and repeatability. Moreover, the biosensor gave a successful application in hydroquinone measurement of river water. This work suggested that the Lac biosensor modified by PANI/CuCNFs has a great potential in the application of phenolic pollutants detection.

Widely used synthetic dyes have been caused serious environmental pollution. Therefore, it is imperative to acquire highly efficient adsorbent to remove them. Here, we report the carbon dots/ZnFe2O4 (CDs/ZFO) composites were prepared through a facile hydrothermal route for absorption removal of dye from aqueous solution. The characterizations reveal the CDs were uniformly deposited on the surfaces of ZFO nanoparticles in the composite. The CDs/ZFO composites as adsorbents exhibit enhanced adsorption behavior for methyl orange (MO) in comparison of pristine ZFO, in which the 5% CDs/ZFO (with the CDs mass content of 5 wt%) shows the highest absorption activity. Experimental studies on adsorption isotherms of MO over the 5% CDs/ZFO composite indicate that experimental data were found to follow Langmuir model with a monolayer adsorption capacity of 181.2 mg g−1. The corresponding adsorption kinetics was fitted well with the pseudo-second-order kinetic model. Moreover, thermodynamics parameters including ΔG°, ΔH° and ΔS° were tested, demonstrating that the adsorption of MO over CDs/ZFO composite was spontaneous and exothermic in nature. The remarkably increased adsorption performance of CDs/ZFO composites can be attributed to abundant oxygen-containing groups on the surface of CDs.

Hematite is an earth-abundant and ubiquitous semiconductor with a suitable bandgap of 2.1 eV for solar water splitting. Unfortunately, it suffers from a low conduction band position compared to the H+/H2 potential and typically an external bias has to be applied. Here, we demonstrate carbon dot-hematite (CD-Fe2O3) nanocomposites as photocatalysts for visible-light-driven overall water splitting without any external bias or scavenger. Notably, the CD-Fe2O3 nanocomposites (carbon dots, 5 wt%) show a hydrogen evolution rate of 0.390 μmol h−1 and an oxygen evolution rate of 0.225 μmol h−1 under visible light illumination. In our system, carbon dots have been well coupled with hematite and are detected to generate a photo-induced potential. This photo-potential can be combined with hematite to meet the requirement for overall water splitting. In addition, carbon dots can significantly improve the charge separation efficiency. Our finding may greatly enhance the practical application of hematite for solar water splitting.

Overall water splitting is considered as one of the most promising strategies to produce renewable energy. Based on low-cost g-C3N4, finding an abundant co-catalyst with high-performance photocatalytic activity and good stability is one of the solutions to realize overall water splitting. We designed amorphous NiO modified g-C3N4 (NiO/g-C3N4) as a photocatalyst, which could achieve efficient visible-light-driven overall water splitting without a sacrificial agent. After adjusting NiO content and calcination temperature, NiO/g-C3N4 with 1.26 wt% NiO content obtained at 300 °C shows optimal overall water splitting performance, with a hydrogen evolution rate of 1.41 μmol h−1 and an oxygen evolution rate of 0.71 μmol h−1 (λ ≥ 420 nm). NiO/g-C3N4 can be reused at least 7 times (24 h each time). The visible-light-driven overall water splitting performance of NiO/g-C3N4 should be attributed to amorphous NiO as the co-catalyst being able to promote photoinduced electron–hole pair separation, provide active sites and help to decompose generated H2O2.

Cadmium sulfide (CdS) has long time been one of the most promising inorganic photocatalysts for hydrogen production driven by visible light. However, the photocorrosion of CdS is the most serious problem which constrains its development. Here, we report the design and fabrication of a carbon dots-cadmium sulfide (CDs-CdS) nanocomposite, showing significant photocatalytic water splitting properties with impressive stability without requirement for any sacrificial agents or cocatalysts. The highest hydrogen production rate was obtained for about 2.55 μmol h −1 , with an oxygen evolution rate for about 0.52 μmol h −1 , when the concentration of CDs in the sample is 0.03 g CDs /g catalyst . Even the produced H 2 and O 2 are not equal to the stoichiometric ratio of 2:1 (H 2 :O 2 ), the CDs-CdS nanocomposite shows greater stability (8-time repetitive catalytic experiments) than the CdS catalysts reported up to now (without sacrificial agents or cocatalysts). It is also inspiring that when we increased the concentration of CDs in the catalysts, the produced H 2 and O 2 were gradually adjusted to meet the stoichiometric ratio of 2:1 in spite of low hydrogen production rate (0.13 μmol h −1 ).

Applying bio-imaging in bacterial viability assessment is vital to human health. Nitrogen, phosphorus co-doped carbon dots (NPCDs) with high visible fluorescence and tunable negative charges were synthesized by a feasible hydrothermal reaction. The as-prepared NPCDs possess abundant surface functional groups, excellent photostability and bio-compatibility. Especially, the surface negative charges of NPCDs can be adjusted by changing the kind of the precursors. The obtained NPCDs as a fluorescent dye could selectively stain dead bacteria instead of live ones due to electrostatic repulsion since the cell walls of bacteria possess negative charges. The NPCDs with less negative charges provides a low accurate mortality rate due to a weaker repulsion, while NPCDs with the most negative charges give a comparable mortality rate with traditional plate counting method but consumes shorter time. Our study suggests that NPCDs with highly negative charges could serve as a precise and efficient fluorescent probe to determine the living state of bacteria, widening the path for bio-imaging application in bacterial viability assessment.

Electrochemical reduction of CO2 is a key component of many prospective artificial technologies for renewable carbon-containing fuels, but it still suffers from the high overpotentials required to drive the process, low selectivity for diversiform products and the high cost of the catalyst. Here, we report that Cu-CDots nanocorals is a highly efficient, low-cost and stable electrocatalyst for CO2 reduction in aqueous solution. The major product of CO2 reduction on the Cu-CDots nanocorals is HCOOH with an inconceivable low overpotential of 0.13 V and a high Faraday efficiency of 79% at a moderate potential of −0.7 V vs. RHE. In the present system, CDots can increase the adsorption capacity of CO2 molecules and H+, which play important roles in CO2 reduction. The high selectivity of HCOOH for CO2 reduction may be ascribed to that CDots can greatly diminish the HCOOH desorption energy and improve the catalytic selectivity for HCOOH. Furthermore, Cu-CDots nanocorals exhibit a long-term stability during 5 h-electrolysis.

Solar water splitting via graphitic carbon nitride (g-C3N4) has achieved extensive attention in recent years. However, g-C3N4 usually suffers from low efficiency and poor stability. Besides, the difficulty lying in the gas mixture separation remains as a big challenge. Herein, a one-pot salt-assisted method was proposed to fabricate the cobalt-doped highly mesoporous g-C3N4 (Co-mCN) photocatalysts for efficient overall water splitting into H2 and H2O2. The adjustable Co doping not only improves the charge separation efficiency, but also enhances the tolerance of g-C3N4 against H2O2 poison. The optimal production for Co-mCN catalysts is gained to be 1.82 μmol h−1 and 1.65 μmol h−1 for H2 and H2O2 respectively, while an apparent quantum efficiency (AQE) of 2.2% at 420 nm and a working life for more than 216 h are also achieved. Moreover, it is demonstrated that the produced H2O2 can be easily collected with titanium silicalite molecular sieve (TS-1) as a reusable H2O2 carrier and directly applied in catalyzing cyclohexane oxidation into cyclohexanone and cyclohexanol mixture with 100% selectivity and 0.11% conversion efficiency. This work provides a new thinking and strategy for realizing overall water splitting, manipulating the products and extending the practical applications of g-C3N4 materials in chemical industry.

A co-based porous metal-organic framework (MOF) of zeolitic imidazolate framework-67 (ZIF-67) and carbon nanofibers (CNFs) was utilized to prepare a ZIF-67/CNFs composite via a one-pot synthesis method. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) were employed to investigate the morphology, structure, and composition of the resulting composite. A novel high-performance non-enzymatic electrochemical sensor was constructed based on the ZIF-67/CNFs composite. The ZIF-67/CNFs based sensor exhibited enhanced electrocatalytic activity towards H2O2 compared to a pure ZIF-67-based sensor, due to the synergistic effects of ZIF-67 and CNFs. Meanwhile, chronoamperometry was utilized to explore the detection performance of the sensor. Results showed the sensor displayed high-efficiency electrocatalysis towards H2O2 with a detection limit of 0.62 &mu, M (S/N = 3), a sensitivity of 323 &micro, A mM&minus, 1 cm&minus, 2, a linear range from 0.0025 to 0.19 mM, as well as satisfactory selectivity and long-term stability. Furthermore, the sensor demonstrated its application potential in the detection of H2O2 in food.

Self-healing is the way by which nature repairs damage and prolongs the life of bio entities. A variety of practical applications require self-healing materials in general and self-healing polymers in particular. Different (complex) methods provide the rebonding of broken bonds, suppressing crack, or local damage propagation. Here, a simple, versatile, and cost-effective methodology is reported for initiating healing in bulk polymers and self-healing and anticorrosion properties in polymer coatings: introduction of carbon dots (CDs), 5 nm sized carbon nanocrystallites, into the polymer matrix forming a composite. The CDs are blended into polymethacrylate, polyurethane, and other common polymers. The healing/self-healing process is initiated by interfacial bonding (covalent, hydrogen, and van der Waals bonding) between the CDs and the polymer matrix and can be optimized by modifying the functional groups which terminate the CDs. The healing properties of the bulk polymer-CD composites are evaluated by comparing the tensile strength of pristine (bulk and coatings) composites to those of fractured composites that are healed and by following the self-healing of scratches intentionally introduced to polymer-CD composite coatings. The composite coatings not only possess self-healing properties but also have superior anticorrosion properties compared to those of the pure polymer coatings.