Achieving high-efficient photocatalytic persulfate-activated degradation of tetracycline via carbon dots modified MIL-101(Fe)octahedrons

The synergistic reaction of photocatalysis and advanced oxidation is a valid strategy for the degradation of harmful antibiotic wastewater.Herein,carbon dots(CDs)modified MIL-101(Fe)octahedrons to form CDs/MIL-101(Fe)composite photocatalyst was synthesized for visible light-driven photocatalytic/persulfate(PS)-activated tetracycline(TC)degradation.The electron spin resonance(ESR)spectra,scavenging experiment and electrochemical analysis were carried out to reveal that the high visible light-driven photocatalytic degradation activity of TC over CDs/MIL-101(Fe)photocatalysts is not only ascribed to the production of free active radicals in the CDs/MIL-101(Fe)/PS system(·OH,·SO_(4-),^(1)O_(2),h^(+)and·O_(2)^(-))but also attributed to the consumption of electrons caused by the PS,which can suppress the recombination of photo-generated carriers as well as strong light scattering and electron trapping effects of CDs.Finally,the possible degradation pathways were proposed by analyzing intermediates via liquid chromatography-mass spectrometry technique.This research presents a rational design conception to construct a CDs/PS-based photocatalysis/advanced oxidation technology with high-efficient degradation activity for the remediation of organic antibiotic pollutant wastewater and for the improvement of carrier transport kinetics of photocatalysts.

High sensitivity detection of baicalein by N,S co⁃doped carbon dots and their application in biofluids

In this work,p⁃phenylenediamine and L⁃cysteine were used as raw materials,and water⁃soluble N,S co⁃doped carbon dots(N,S⁃CDs)with excellent performance were prepared through a one⁃step solvothermal method.The morphology and structure of N,S⁃CDs were characterized by transmission electron microscope,X⁃ray diffrac⁃tion,Fourier transform infrared spectroscopy,and X⁃ray photoelectron spectroscopy,and the basic photophysical properties were investigated via UV⁃Vis absorption spectra and fluorescence spectra.Meanwhile,the N,S⁃CDs have excellent luminescence stability with pH,ionic strength,radiation time,and storage time.Experimental results illus⁃trated the present sensor platform exhibited high sensitivity and selectivity in response to baicalein with a detection limit of 85 nmol·L-1.The quenching mechanism is proved to be the inner filter effect.In addition,this sensor can also detect baicalein in biofluids(serum and urine)with good accuracy and reproducibility.

Accelerating H^(*)desorption of hollow Mo_(2)C nanoreactor via in-situ grown carbon dots for electrocatalytic hydrogen evolution

Molybdenum carbide(Mo_(2)C)is a promising non-noble metal electrocatalyst with electronic structures similar to Pt for hydrogen evolution reaction(HER).However,strong H^(*)adsorption at the Mo sites hinders the improvement of HER performance.Here,we synthesized monodisperse hollow Mo_(2)C nanoreactors,in which the carbon dots(CD)were in situ formed onto the surface of Mo_(2)C through carburization reactions.According to finite element simulation and analysis,the CD@Mo_(2)C possesses better mesoscale diffusion properties than Mo_(2)C alone.The optimized CD@Mo_(2)C nanoreactor demonstrates superior HER performance in alkaline electrolyte with a low overpotential of 57 mV at 10 mA cm^(−2),which is better than most Mo_(2)C-based electrocatalysts.Moreover,CD@Mo_(2)C exhibits excellent electrochemical stability during 240 h,confirmed by operando Raman and X-ray diffraction(XRD).Density functional theory(DFT)calculations show that carbon dots cause the d-band center of CD@Mo_(2)C to shift away from Fermi level,promoting water dissociation and the desorption of H^(*).This study provides a reasonable strategy towards high-activity Mo-based HER eletrocatalysts by modulating the strength of Mo–H bonds.

High Colloidal Stable Carbon Dots Armored Liquid Metal Nano-Droplets for Versatile 3D/4D Printing Through Digital Light Processing(DLP)

Liquid metal(LM)and liquid metal alloys(LMs)possess unique physicochemical features,which have become emerging and functionalized materials that are attractive applicants in various fields.Herein,uniform LM nanodroplets armored by carbon dots(LMD@CDs)were prepared and exhibited high colloidal stability in various solvents,as well as water.After optimization,LMD@CDs can be applied as functional additives for the 3D/4D printing of hydrogel and cross-linked resin through digital light processing(DLP).The light absorption of LMD@CDs not only improved the printing accuracy,but also led to the cross-linking density differential during the post-curing process.Base on the cross-linking density differential of soft hydrogel and photothermal performance of the LM,the 3D printed objects can exhibit stimulus responses to both water and laser irradiation.Additionally,the CDs shell and LM core of LMD@CDs provide the printed objects interesting photoluminescence and electric conductivity capabilities,respectively.We deduce this versatile 3D/4D printing system would provide a new platform for the preparation of multi-functional and stimuli-responsive advance materials.

NH_(3)‑Induced In Situ Etching Strategy Derived 3D‑Interconnected Porous MXene/Carbon Dots Films for High Performance Flexible Supercapacitors

2D MXene(Ti_(3)CNT_(x))has been considered as the most promising electrode material for flexible supercapacitors owing to its metallic conductivity,ultra-high capacitance,and excellent flexibility.However,it suffers from a severe restacking problem during the electrode fabrication process,limiting the ion transport kinetics and the accessibility of ions in the electrodes,especially in the direction normal to the electrode surface.Herein,we report a NH_(3)-induced in situ etching strategy to fabricate 3D-interconnected porous MXene/carbon dots(p-MC)films for high-performance flexible supercapacitor.The pre-intercalated carbon dots(CDs)first prevent the restacking of MXene to expose more inner electrochemical active sites.The partially decomposed CDs generate NH_(3)for in situ etching of MXene nanosheets toward 3D-interconnected p-MC films.Benefiting from the structural merits and the 3D-interconnected ionic transmission channels,p-MC film electrodes achieve excellent gravimetric capacitance(688.9 F g^(-1)at 2 A g^(-1))and superior rate capability.Moreover,the optimized p-MC electrode is assembled into an asymmetric solid-state flexible supercapacitor with high energy density and superior cycling stability,demonstrating the great promise of p-MC electrode for practical applications.

Functionalized carbon dots for corrosion protection:Recent advances and future perspectives

Metal corrosion causes significant economic losses,safety issues,and environmental pollution.Hence,its prevention is of immense research interest.Carbon dots(CDs)are a new class of zero-dimensional carbon nanomaterials,which have been considered for corrosion protection applications in recent years due to their corrosion inhibition effect,fluorescence,low toxicity,facile chemical modification,and cost-effectiveness.This study provides a comprehensive overview of the synthesis,physical and chemical properties,and anticorrosion mechanisms of functionalized CDs.First,the corrosion inhibition performance of different types of CDs is introduced,followed by discussion on their application in the development of smart protective coatings with self-healing and/or self-reporting properties.The effective barrier formed by CDs in the coatings can inhibit the spread of local damage and achieve self-healing behavior.In addition,diverse functional groups on CDs can interact with Fe^(3+)and H^(+)ions generated during the corrosion process;this interaction changes their fluorescence,thereby demonstrating self-reporting behavior.Moreover,challenges and prospects for the development of CD-based corrosion protection systems are also presented.

Surface passivation by multifunctional carbon dots toward highly efficient and stable inverted perovskite solar cells

Interfacial imperfections between the perovskite layer and the electron transport layer(ETL)in perovskite solar cells(PSCs)can lead to performance loss and negatively influence long-term operational stability.Here,we introduce an interface engineering method to modify the interface between perovskite and ETL by using multifunctional carbon dots(CDs).C=O in the CDs can chelate with the uncoordinated Pb2+in the perovskite material,inhibit interfacial recombination,and enhance the performance and stability of device.In addition,–OH in CDs forms hydrogen bonds with I-and organic cation in perovskite,inhibiting light-induced I2release and organic cation volatilization,causing irreversible degradation of perovskite films,thereby enhancing the long-term operational stability of PSCs.Consequently,we achieve the champion inverted device with an efficiency of 24.02%.The CDs-treated PSCs exhibit high operational stability,and the maximum power point tracking only attenuates by 12.5%after 1000 h.Interfacial modification engineering supported by multifunctional quantum dots can accelerate the road to stable PSCs.

A recent update on development,synthesis methods,properties and application of natural products derived carbon dots

Natural resources are practically infinitely abundant in nature,which stimulates scientists to create new materials with inventive uses and minimal environmental impact.Due to the various benefits of natural carbon dots(NCDs)from them has received a lot of attention recently.Natural products-derived carbon dots have recently emerged as a highly promising class of nanomaterials,showcasing exceptional properties and eco-friendly nature,which make them appealing for diverse applications in various fields such as biomedical,environmental sensing and monitoring,energy storage and conversion,optoelectronics and photonics,agriculture,quantum computing,nanomedicine and cancer therapy.Characterization techniques such as Photoinduced electron transfer,Aggregation-Induced-Emission(AIE),Absorbance,Fluorescence in UV-Vis and NIR Regions play crucial roles in understanding the structural and optical properties of Carbon dots(CDs).The exceptional photoluminescence properties exhibited by CDs derived from natural products have paved the way for applications in tissue engineering,cancer treatment,bioimaging,sensing,drug delivery,photocatalysis,and promising remarkable advancements in these fields.In this review,we summarized the various synthesis methods,physical and optical properties,applications,challenges,future prospects of natural products-derived carbon dots etc.In this expanding sector,the difficulties and prospects for NCD-based materials research will also be explored.

Controllable Synthesis of Fluorescent Carbon Dots and Their Detection Application as Nanoprobes

Carbon dots(CDs), as a new member of carbon nanomaterial family, have aroused great interest since their discovery in 2004. Because of their outstanding water solubility, high sensitivity and selectivity to target analytes, low toxicity, favorable biocompatibility, and excellent photostability, researchers from diverse disciplines have come together to further develop the fundamental properties of CDs. Many methods for the production of CDs have been reported, therein, hydrothermal and solvothermal technology needs simple equipments, and microwave synthesis needs less reaction time, hence these methods become current common synthesis methods, in which many precursors have been applied to produce CDs. Due to their excellent fluorescence, CDs have made impressive strides in sensitivity and selectivity to a diverse array of salt ions,organic/biological molecules and target gases. The development of CDs as nanoprobes is still in its infancy, but continued progress may lead to their integration into environmental and biological applications. Hydrothermal,solvothermal, and microwave synthesis of fluorescent carbon dots and their detection applications as nanoprobes in salt ions, organic/biological molecules, and target gases will be reviewed.

Biogreen Synthesis of Carbon Dots for Biotechnology and Nanomedicine Applications

Over the past decade, carbon dots have ignited a burst of interest in many different fields, including nanomedicine, solar energy, optoelectronics, energy storage,and sensing applications, owing to their excellent photoluminescence properties and the easiness to modify their optical properties through doping and functionalization. In this review, the synthesis, structural and optical properties,as well as photoluminescence mechanisms of carbon dots are first reviewed and summarized. Then, we describe a series of designs for carbon dot-based sensors and the different sensing mechanisms associated with them.Thereafter, we elaborate on recent research advances on carbon dot-based sensors for the selective and sensitive detection of a wide range of analytes, including heavy metals, cations, anions, biomolecules, biomarkers,nitroaromatic explosives, pollutants, vitamins, and drugs.Lastly, we provide a concluding perspective on the overall status, challenges, and future directions for the use of carbon dots in real-life sensing.

Corrosion protection investigations of carbon dots and polydopamine composite coating on magnesium alloy

A composite coating of nitrogen-doped carbon dots(N–CDs)and polydopamine(PDA)was prepared on magnesium alloy by combining electrodeposition with dip coating methods.The microstructure of the N–CDs/PDA composite coating,including composition,surface morphology,and crystalline structure,is characterized by Raman spectroscopy,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy,respectively.The corrosion protection performances of the composite coating are evaluated by potentiodynamic polarization tests,electrochemical impedance spectroscopy,and salt spray tests.The effect of the particle size of the N–CDs on the corrosion performance is also investigated.The results show that the corrosion performance of the N–CDs coatings are enhanced with the increase of the particle sizes.Furthermore,an obvious self-healing performance is observed on the surface of the N–CDs/PDA composite coating.These results indicate that N–CDs/PDA composite coating can improve the corrosion performance of the Mg alloy,and open a new design direction for the protective coating of metallic materials.

Facile and Scalable Preparation of Fluorescent Carbon Dots for Multifunctional Applications

The synthesis of fluorescent nanomaterials has received considerable attention due to the great potential of these materials for a wide range of applications, from chemical sensing through bioimaging to optoelectron- ics. Herein, we report a facile and scalable approach to prepare fluorescent carbon dots （FCDs） via a one-pot reaction of citric acid with ethylenediamine at 150 ℃ under ambient air pressure. The resultant FCDs pos- sess an optical bandgap of 3.4 eV and exhibit strong excitation-wavelength-independent blue emission （λEm = 450 nm） under either one- or two-photon excitation. Owing to their low cytotoxicity and long fluorescence lifetime, these FCDs were successfully used as internalized fluorescent probes in human cancer cell lines （HeLa cells） for two-photon excited imaging of cells by fluorescence lifetime imaging microscopy with a high-contrast resolution. They were also homogenously mixed with commercial inks and used to draw fluo- rescent patterns on normal papers and on many other substrates （e.g., certain flexible plastic films, textiles, and clothes）. Thus, these nanomaterials are promising for use in solid-state fluorescent sensing, security labeling, and wearable optoelectronics.

Interface electron collaborative migration of Co–Co3O4/carbon dots:Boosting the hydrolytic dehydrogenation of ammonia borane

Ammonia borane(AB)is an excellent candidate for the chemical storage of hydrogen.However,its practical utilization for hydrogen production is hindered by the need for expensive noble-metal-based catalysts.Herein,we report Co-Co3O4 nanoparticles(NPs)facilely deposited on carbon dots(CDs)as a highly efficient,robust,and noble-metal-free catalyst for the hydrolysis of AB.The incorporation of the multiinterfaces between Co,Co3O4 NPs,and CDs endows this hybrid material with excellent catalytic activity(rB=6816 mLH2 min^-1 gCo^-1)exceeding that of previous non-noble-metal NP systems and even that of some noble-metal NP systems.A further mechanistic study suggests that these interfacial interactions can affect the electronic structures of interfacial atoms and provide abundant adsorption sites for AB and water molecules,resulting in a low energy barrier for the activation of reactive molecules and thus substantial improvement of the catalytic rate.

Green and Near-Infrared Dual-Mode Afterglow of Carbon Dots and Their Applications for Confidential Information Readout

Near-infrared(NIR),particularly NIR-containing dual-/multimode afterglow,is very attractive in many fields of application,but it is still a great challenge to achieve such property of materials. Herein,we report a facile method to prepare green and NIR dual-mode afterglow of carbon dots(CDs) through in situ embedding o-CDs(being prepared from o-phenylenediamine) into cyanuric acid(CA) matrix(named o-CDs@CA). Further studies reveal that the green and NIR afterglows of o-CDs@CA originate from thermal activated delayed fluorescence(TADF) and room temperature phosphorescence(RTP) of o-CDs,respectively. In addition,the formation of covalent bonds between o-CDs and CA,and the presence of multiple fixation and rigid e ects to the triplet states of o-CDs are confirmed to be critical for activating the observed dual-mode afterglow. Due to the shorter lifetime and insensitiveness to human vision of the NIR RTP of o-CDs@CA,it is completely covered by the green TADF during directly observing. The NIR RTP signal,however,can be readily captured if an optical filter(cut-o wavelength of 600 nm) being used. By utilizing these unique features,the applications of o-CDs@CA in anti-counterfeiting and information encryption have been demonstrated with great confidentiality. Finally,the as-developed method was confirmed to be applicable to many other kinds of CDs for achieving or enhancing their afterglow performances.

Solar-Driven Hydrogen Peroxide Production Using Polymer-Supported Carbon Dots as Heterogeneous Catalyst

Safe, sustainable, and green production of hydro gen peroxide is an exciting proposition due to the role of hydrogen peroxide as a green oxidant and energy carrier for fuel cells. The current work reports the development of carbon dot-impregnated waterborne hyperbranched polyurethane as a heterogeneous photo-catalyst for solar-driven production of hydrogen peroxide. The results reveal that the carbon dots possess a suitable band-gap of 2.98 eV,which facilitates effective splitting of both water and ethanol under solar irradiation. Inclusion of the carbon dots within the eco-friendly polymeric material ensures their catalytic activity and also provides a facile route for easy catalyst separation, especially from a solubilizing medium.The overall process was performed in accordance with the principles of green chemistry using bio-based precursorsand aqueous medium. This work highlights the potential of carbon dots as an effective photo-catalyst.

Amorphous CoOx coupled carbon dots as a spongy porous bifunctional catalyst for efficient photocatalytic water oxidation and CO2 reduction

Cobalt-based oxides,with high abundance,good stability and excellent catalytic performance,are regarded as promising photocatalysts for artificial photosynthetic systems to alleviate foreseeable energy shortages and global warming.Herein,for the first time,a series of novel spongy porous CDs@CoOx materials were synthesized to act as an efficient and stable bifunctional photocatalyst for water oxidation and CO2 reduction.Notably,the preparation temperatures visibly influence the morphologies and photocatalytic performances of the CDs@CoOx.Under the optimal conditions,a maximum O2 yield of 40.4% and pretty apparent quantum efficiency(AQE)of 58.6% at 460 nm were obtained over CDs@CoOx-300 for water oxidation.Similarly,the optimized sample CDs@CoOx-300 manifests significant enhancement on the CO2-to-CO conversion with a high selectivity of 89.3% and CO generation rate of 8.1μmol/h,which is superior to most previous cobalt-based catalysts for CO2 reduction.The composite CDs@CoOx-300 not only exposes more active sites but also facilitates electron transport,which results in excellent photocatalytic activity.In addition,the boosted photocatalytic behavior is attributed to the synergistic effect between CoOx and CDs,which was verified by the photocatalytic activity control experiments and electrochemical characterization.The work offers a novel strategy to fabricate a high performance bifunctional photocatalyst for water oxidation and CO2 reduction.

Carbon dots regulate the interface electron transfer and catalytic kinetics of Pt-based alloys catalyst for highly efficient hydrogen oxidation

The regulation of interface electron-transfer and catalytic kinetics is very important to design the efficient electrocatalyst for alkaline hydrogen oxidation reaction(HOR).Here,we show the Pt-Ni alloy nanoparticles(PtNi_(2))have an enhanced HOR activity compared with single component Pt catalyst.While,the interface electron-transfer kinetics of PtNi_(2)catalyst exhibits a very wide electron-transfer speed distribution.When combined with carbon dots(CDs),the interface charge transfer of PtNi_(2)-CDs composite is optimized,and then the PtNi_(2)-5 mg CDs exhibits about 2.67 times and 4.04 times higher mass and specific activity in 0.1 M KOH than that of 20%commercial Pt/C.In this system,CDs also contribute to trapping H^(+)and H_(2)O generated during HOR,tuning hydrogen binding energy(HBE),and regulating interface electron transfer.This work provides a deep understanding of the interface catalytic kinetics of Pt-based alloys towards highly efficient HOR catalysts design.

Carbon dot-modified silicon nanoparticles for lithium-ion batteries

Silicon(Si)particles were functionalized using carbon dots(CDs)to enhance the interaction between the Si particles and the binders.First,CDs rich in polar groups were synthesized using a simple hydrothermal method.Then,CDs were loaded on the Si surface by impregnation to obtain the functionalized Si particles(Si/CDs).The phases and microstructures of the Si/CDs were observed using Fourier-transform infrared reflection,X-ray diffraction,scanning electron microscopy,and high-resolution transmission electron microscopy.Si/CDs were used as the active material of the anode for electrochemical performance experiments.The electrochemical performance of the Si/CD electrode was assessed using cyclic voltammetry,electrochemical impedance spectroscopy,and constant current charge and discharge experiment.The electrodes prepared with Si/CDs showed good mechanical structure stability and electrochemical performance.After 150 cycles at 0.2 C,the capacity retention rate of the Si/CD electrode was 64.0%,which is twice as much as that of pure Si electrode under the same test conditions.

Carbon dots-derived carbon nanoflowers decorated with cobalt single atoms and nanoparticles as efficient electrocatalysts for oxygen reduction

The sluggish kinetics of oxygen reduction reaction(ORR)hinders the commercialization of Zn‐air batteries(ZABs).Manipulating the electronic structure of electrocatalysts to optimize the adsorption energy of oxygen‐containing intermediates during the 4e–ORR offers a practical route toward improving ORR kinetics.Herein,we designed a novel ORR electrocatalyst containing Co single atoms and nanoparticles supported by carbon dots‐derived carbon nanoflowers(Co SAs/NPs CNF).Co SAs/NPs CNF possessed a very high ORR activity(E_(1/2) of the Co SAs/NPs CNF catalyst is 0.83 V(vs.RHE)),and outstanding catalytic performance and stability when used as the air‐electrode catalyst in rechargeable ZABs(152.32 mW cm^(-2),1000.58 mWh gZn^(–1),and over 1300 cycles at a current density of 5 mA cm^(-2)).The Co SAs and Co NPs cooperated to improve electron and proton transfer processes during ORR.Theoretical calculations revealed that the presence of adjacent Co NPs optimized the electronic structure of the isolated Co‐N_(4) sites,significantly lowering the energy barriers for the rate‐determining step in ORR(adsorption of*OOH)and thereby delivering outstanding ORR performance.This work reveals that the combination of supported single‐atom sites and metal nanoparticles can be highly beneficial for ORR electrocatalysis,outperforming catalysts containing only Co SAs or Co NPs.

A review of carbon dots and their composite materials for electrochemical energy technologies

Carbon dots(CDs)and their composites as energy storage materials and electrocatalysts have emerged as new types of quasi-zero-dimensional carbon materials.CDs can provide a large specific surface area,numerous electron-electron hole pairs,adjustable heteroatom doping,rich surface functional groups,and so on.However,the roles and functional mechanisms of CDs and their composite materials in the enhancement of electrochemical performance remain unclear and need to be understood in depth.Based on the most recent literature,this paper comprehensively reviews the synthesis methods and applications of various categories of CDs and their composites as electrode materials of supercapacitors,lithium-ion batteries,sodium-ion batteries,and potassium-ion batteries,and as electrocatalysts for hydrogen evolution,oxygen evolution,and oxygen reduction reactions in metal-air batteries,fuel cells,and water electrolysis.To facilitate further research and development,several important aspects related to CDs and their composite materials are summarized with analysis of the technical challenges in practical applications and discussion of the possible development perspectives.