The development of lithium-sulfur(Li-S) battery as one of the most attractive energy storage systems among lithium metal batteries is seriously hindered by low sulfur utilization, poor cycle stability and uneven redep...The development of lithium-sulfur(Li-S) battery as one of the most attractive energy storage systems among lithium metal batteries is seriously hindered by low sulfur utilization, poor cycle stability and uneven redeposition of Li anode. It is necessary to propose strategies to address the problems as well as improve the electrochemical performance. One of the effective solutions is to improve the sulfiphilicity of sulfur cathode and the lithiophilicity of the Li anode. Herein, we reported that a synergistic functional separator(graphene quantum dots(GQDs)-polyacrylonitrile(PAN) @polypropylene(PP) separator)improved the electrochemical activity of sulfur cathode as well as the stability of Li anode. GQDs induced uniform Li^(+)nucleation and deposition, which slowed down the passivation of Li anode and avoided shortcircuit. Further, three-dimensional network constructed by electrospinning nanofibers and the polar functional groups of GQDs could both effectively inhibit the shuttle of LiPSs and improve the sulfur utilization. The stability of Li-S battery was improved by the synergistic effect. In addition, GQDs and electrospinning nanofibers protector increased lifetime of separators. Benefiting from the unique design strategy, Li//Li symmetric battery with GQDs-PAN@PP separators exhibited stably cycling for over 600 h. More importantly, the Li-S full batteries based GQDs-PAN@PP separators enabled high stability and desirable sulfur electrochemistry, including high reversibility of 558.09 mA h g^(-1)for 200 cycles and durable life with a low fading rate of 0.075% per cycle after 500 cycles at 0.5 C. Moreover, an impressive areal capacity of 3.23 mA h cm^(-2)was maintained under high sulfur loading of 5.10 mg cm^(-2). This work provides a new insight for modification separator to improve the electrochemical performance of Li-S/Li metal batteries.展开更多
Cost-effective,safe,and highly performing energy storage devices require rechargeable batteries,and among various options,aqueous zinc-ion batteries(ZIBs)have shown high promise in this regard.As a cathode material fo...Cost-effective,safe,and highly performing energy storage devices require rechargeable batteries,and among various options,aqueous zinc-ion batteries(ZIBs)have shown high promise in this regard.As a cathode material for the aqueous ZIBs,manganese dioxide(MnO_(2))has been found to be promising,but certain drawbacks of this cathode material are slow charge-transfer capability and poor cycling performance.Herein,a novel design of graphene quantum dots(GQDs)integrated with Zn-intercalated MnO_(2)nanosheets is put forward to construct a 3D nanoflower-like GQDs@ZnxMnO_(2)composite cathode for aqueous ZIBs.The synergistic coupling of GQDs modification with Zn intercalation provides abundant active sites and conductive medium to facilitate the ion/electron transmission,as well as ensure the GQDs@ZnxMnO_(2)composite cathode with enhanced charge-transfer capability and high electrochemical reversibility,which are elucidated by experiment results and in-situ Raman investigation.These impressive properties endow the GQDs@ZnxMnO_(2)composite cathode with superior aqueous Zn^(2+) storage capacity(~403.6 mAh·g^(−1)),excellent electrochemical kinetics,and good structural stability.For actual applications,the fabricated aqueous ZIBs can deliver a substantial energy density(226.8 W·h·kg^(−1)),a remarkable power density(650 W·kg^(−1)),and long-term cycle performance,further stimulating their potential application as efficient electrochemical storage devices for various energy-related fields.展开更多
Pervaporation desalination by highly hydrophilic materials such as poly(vinyl alcohol)(PVA)based separation membrane is a burgeoning technology of late years.However,the improvement of membrane flux in pervaporation d...Pervaporation desalination by highly hydrophilic materials such as poly(vinyl alcohol)(PVA)based separation membrane is a burgeoning technology of late years.However,the improvement of membrane flux in pervaporation desalination has been a difficult task.Here,a novel hybrid membrane with doped graphene oxide quantum dots(GOQDs)which is rich in hydrophilic groups and small size into the matrix of PVA was prepared to improve the membrane flux.The membranes structures were described by field emission scanning electron microscopy(FESEM),atomic force microscopy(AFM),Fourier transform infrared(FT-IR),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA)and X-ray diffraction(XRD).And more,Water contact angle,swelling degree,and pervaporation properties were carried out to explore the effect of GOQDs in PVA matrix.In addition,GOQDs content in the hybrid membrane,NaCl concentration,and feed temperature were investigated accordingly.Moreover,the hydrogen bonds between PVA chains were weakened by the interaction between GOQDs and PVA chains.Significantly,the hybrid membrane with optimized doped GOQDs content,200 mg·L^(-1),displays a high membrane flux of 17.09 kg·m^(-2)·h^(-1)and the salt rejection is consistently greater than 99.6%.展开更多
Coal-based graphene quantum dots(GQDs) were successfully produced via a one-step chemical synthesis from six different coal ranks, from which two superhigh organic sulfur(SHOS) coals were selected as natural S-doped c...Coal-based graphene quantum dots(GQDs) were successfully produced via a one-step chemical synthesis from six different coal ranks, from which two superhigh organic sulfur(SHOS) coals were selected as natural S-doped carbon sources for the preparation of S-doped GQDs. The effects of coal properties on coal-based GQDs were analyzed by means of high-resolution transmission electron microscopy(HRTEM), X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, X-ray photoelectron spectroscopy(XPS), ultraviolet-visible(UV-Vis) absorption spectroscopy, and fluorescence emission spectra. It was shown that all coal samples can be used to prepare GQDs, which emit bluegreen and blue fluorescence under ultraviolet light. Anthracite-based GQDs have a hexagonal crystal structure without defects, the largest size, and densely arranged carbon rings in their lamellae; the highrank bituminous coal-based GQDs are relatively reduced in size, with their hexagonal crystal structure being only faintly visible; the low-rank bituminous coal-based GQDs are the smallest, with sparse lattice fringes and visible internal defects. As the metamorphism of raw coals increases, the yield decreases and the fluorescence quantum yield(QY) initially increases and then decreases. Additionally, the surface of GQDs that were prepared using high-rank SHOS coal(high-rank bituminous coal) preserves rich sulfur content even after strong oxidation, which effectively adjusts the bandgap and improves the fluorescence QY. Thus, high-rank bituminous coal with SHOS content can be used as a natural S-doped carbon source to prepare S-doped GQDs, extending the clean utilization of low-grade coal.展开更多
Objective To evaluate the bio-safety of graphene quantum dots (GQDs), we studied its effects on the embryonic development of zebrafish. Methods In vivo, biodistribution and the developmental toxicity of GQDs were in...Objective To evaluate the bio-safety of graphene quantum dots (GQDs), we studied its effects on the embryonic development of zebrafish. Methods In vivo, biodistribution and the developmental toxicity of GQDs were investigated in embryonic zebrafish at exposure concentrations ranging from 12.5-200μg/mL for 4-96 h post-fertilization (hpf). The mortality, hatch rate, malformation, heart rate, GQDs uptake, spontaneous movement, and larval behavior were examined. Results The fluorescence of GQDs was mainly localized in the intestines and heart. As the exposure concentration increased, the hatch and heart rate decreased, accompanied by an increase in mortality. Exposure to a high level of GQDs (200μg/mL) resulted in various embryonic malformations including pericardial edema, vitelline cyst, bent spine, and bent tail. The spontaneous movement significantly decreased after exposure to GQDs at concentrations of 50, 100, and 200μg/mL. The larval behavior testing (visible light test) showed that the total swimming distance and speed decreased dose-dependently. Embryos exposed to 12.5 μg/mL showed hyperactivity while exposure to higher concentrations (25, 50, 100, and 200μg/mL) caused remarkable hypoactivity in the light-dark test. Conclusion Low concentrations of GODs were relatively non-toxic. However, GQDs disrupt the progression of embryonic development at concentrations exceeding 50 μg/mL.展开更多
Graphene quantum dots(GQDs)which are nanofragments of graphene with an average size between 2 and 50 nm have attracted much attention due to their outstanding properties such as high conductivity,high surface area,and...Graphene quantum dots(GQDs)which are nanofragments of graphene with an average size between 2 and 50 nm have attracted much attention due to their outstanding properties such as high conductivity,high surface area,and good solubility in various solvents.GQDs combine the quantum confinement and edges effects and the properties of graphene.Therefore,GQDs offers a broad range of applications in various fields(medicine,energy conversion,and energy storage devices).This review will present the recent research based on the introduction of GQDs in batteries,supercapacitors,and microsupercapacitors as electrodes materials or mixed with an active material as an auxiliary agent.Tables,discussed on selected examples,summarize the electrochemical performances and finally,challenges and perspectives are recalled for the subsequent optimization strategy of electrode materials.This review is expected to appeal a broad interest on functional GQDs materials and promote the further development of high-performance energy storage device.展开更多
Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe cons...Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.展开更多
We report a facile method of synthesizing graphene quantum dots(GQDs) with tunable emission. The as-prepared GQDs each with a uniform lateral dimension of ca. 6 nm have fine solubility and high stability. The photol...We report a facile method of synthesizing graphene quantum dots(GQDs) with tunable emission. The as-prepared GQDs each with a uniform lateral dimension of ca. 6 nm have fine solubility and high stability. The photoluminescence mechanism is further investigated based on the surfacestructure and the photoluminescence behaviors. Based on our discussion, the green fluorescence emission can be attributed to the oxygen functional groups, which could possess broad emission bands within the π –π * gap. This work is helpful to explain the vague fluorescent mechanism of GQDs, and the reported synthetic method is useful to prepare GQDs with controllable fluorescent colors.展开更多
Graphene quantum dots(GQDs)are two-dimensional carbon nano-material with excellent physicochemical properties,including biocompatibility,high photoluminescence,water-solubility,hypotoxicity and so on.Owing to bigπ-co...Graphene quantum dots(GQDs)are two-dimensional carbon nano-material with excellent physicochemical properties,including biocompatibility,high photoluminescence,water-solubility,hypotoxicity and so on.Owing to bigπ-conjugated structure and oxygen-containing functional groups,GQDs have the ability to absorb various chemical drugs viaπ-πstacking and electrostatic interaction.On the other hand,owning to photoluminescence,GQDs also have potential to serve as fluorescence probe for bioimaging,especially for optical diagnostics.In addition,GQDs have the ability to generate reactive oxygen species(ROS)including singlet oxygen upon photoexcitation.Therefore,GQDs are likely to be used for photodynamic therapy.This article aims to review the frontier researches about GQDs in the field of fluorescence probe,photodynamic therapy and anti-tumor drug delivery system.展开更多
We demonstrated a facile method to prepare photoluminescent graphene quantum dots using commercial polyacrylonitrile(PAN) based carbon fibers(CFs) as the raw material by facile chemical oxidation and exfoliation m...We demonstrated a facile method to prepare photoluminescent graphene quantum dots using commercial polyacrylonitrile(PAN) based carbon fibers(CFs) as the raw material by facile chemical oxidation and exfoliation method. The as-prepared GQDs with uniform size exhibit an excitation-independent photoluminescence behavior, which is similar to other semiconductor quantum dots. Moreover, when acting as catalyst the uniform GQDs have better activity for electrochemical oxidation of dopamine(DA) than graphene oxides(GOs). The square wave voltammogram(SWV) peak values of GQDs are in good correspondence with DA concentrations and can act as a sensor of DA.展开更多
Reduced graphene oxide(rGO)membranes have been intensively evaluated for desalination and ionic sieving applications,benefiting from their stable and well-confined interlayer channels.However,rGO membranes generally s...Reduced graphene oxide(rGO)membranes have been intensively evaluated for desalination and ionic sieving applications,benefiting from their stable and well-confined interlayer channels.However,rGO membranes generally suffer from low permeability due to the high transport resistance resulting from the narrowed two-dimensional(2D)channels.Although high permeability can be realized by reducing membrane thickness,membrane selectivity normally declines because of the formation of nonselective defects,in particular pinholes.In this study,we demonstrate that the non-selective defects in ultrathin rGO membranes can be effectively minimised by a facile posttreatment via surfacedeposition of graphene quantum dots(GQDs).The resultant GQDs/rGO membranes obtained a good trade-off between water permeance(14 L·m^(-2)·h^(-1).MPa^(-1))and NaCl rejection(91%).This work provides new insights into the design of high quality ultrathin 2D laminar membranes for desalination,molecular/ionic sieving and other separation applications.展开更多
The substrate treatment with seeding promoter can promote the two-dimensional material lateral growth in chemical vapor deposition (CVD) process. Herein, graphene quantum dots (GQDs) as a novel seeding promoter w...The substrate treatment with seeding promoter can promote the two-dimensional material lateral growth in chemical vapor deposition (CVD) process. Herein, graphene quantum dots (GQDs) as a novel seeding promoter were used to obtain uniform large-area MoS2 monolayer. The obtained monolayer MoS2 films were confirmed by optical microscope, scanning electron microscope, Raman and photoluminescence spectra. Raman mapping revealed that the MoS2 monolayer was largely homogeneous.展开更多
A modulated photoluminescence nanosensor was developed for the quantitative detection of formaldehyde with nitrogen-doped graphene quantum dots and melamine. The sensing system was based on the different activated eff...A modulated photoluminescence nanosensor was developed for the quantitative detection of formaldehyde with nitrogen-doped graphene quantum dots and melamine. The sensing system was based on the different activated effects of melamine and hydrogen peroxide on the photoluminescence intensity of nitrogendoped graphene quantum dots. Under the optimal conditions, the modulated photoluminescence sensing system can be used to detect formaldehyde with a good linear relationship between the nitrogen-doped graphene quantum dots photoluminescence difference and the concentration of formaldehyde. The novel sensing system provided new directions for the detection of formaldehyde with high selectivity and quick response.展开更多
CdSe quantum dot sensitized solar cells (QDSCs) modified with graphene quantum dots (GQDs) have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage (Voc) of the...CdSe quantum dot sensitized solar cells (QDSCs) modified with graphene quantum dots (GQDs) have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage (Voc) of the modified QDSCs was approximately 0.04 V higher than that of plain CdSe QDSCs, consequently improving the photovoltaic performance of the resulting QDSCs. Served as a novel coating on the CdSe QD sensitized photoanode, GQDs played a vital role in improving Voc due to the suppressed charge recombination which has been confirmed by electron impedance spectroscopy as well as transient photovoltage decay measure- ments. Moreover, different adsorption sequences, concentration and deposition time of GQDs have also been systematically investigated to boost the power conversion efficiency (PCE) of CdSe QDSCs. After the coating of CdSe with GQDs, the resulting champion CdSe QDSCs exhibited an improved PCE of 6.59% under AM 1.5G full one sun illumination.展开更多
Zero-dimensional graphene quantum dots(GQDs)exhibit many different properties,such as strong fluorescence,nonzero bandgap and solubility in solvents,compared to two-dimensional graphene.GQDs are biocompatible and have...Zero-dimensional graphene quantum dots(GQDs)exhibit many different properties,such as strong fluorescence,nonzero bandgap and solubility in solvents,compared to two-dimensional graphene.GQDs are biocompatible and have low toxicity;hence,they are widely used in the biomedical field.The edge effect of GQDs is of particular interest because edge modification can regulate the performance of nanomaterials.In this review,various preparation methods for GQDs,which can be divided into three main categories,namely top-down,bottom-up and chemical methods,are discussed.The unique optical,electrical,thermal and magnetic properties of GQDs are reviewed.The functionalization of GQDs by doping with heteroatoms and forming composites with other materials is studied,and the characteristics of these GQDs are also discussed.The applications of these GQDs in the fields of optics,electricity,optoelectronics,biomedicine,energy,agriculture and other emerging interdisciplinary fields are reviewed to highlight the enormous potential of nanomaterials.This review reports on the recent advancement in GQD research and suggests future directions for the development of GQDs.展开更多
Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology r...Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.展开更多
Graphene quantum dots(GQDs)refer to graphene fragments with a lateral dimension typically less than 100 nm,which possess unique electrical and optical properties due to the quantum confinement effect.In this study,we ...Graphene quantum dots(GQDs)refer to graphene fragments with a lateral dimension typically less than 100 nm,which possess unique electrical and optical properties due to the quantum confinement effect.In this study,we demonstrate that chemically derived graphene quantum dots show great potential for making highly stretchable and cost-effective strain sensors via an electron tunneling mechanism.Stretch-able strain sensors are critical devices for the field of flexible or wearable electronics which are expected to maintain function up to high strain values(>30%).However,strain sensors based on conventional materials(i.e.metal or semiconductors)or metal nanoparticles(e.g.gold or silver nanoparticles)only work within a small range of strain(i.e.the former have a working range<1%and the latter<3%).In this study,by simply dropcasting solution-processed GQDs between the interdigitated electrodes on polydimethylsiloxane,we obtained devices that can function in the range from 0.06%to over 50%ten-sile strain with both the sensitivity and working range conveniently adjustable by the concentration of GQDs applied.This study provides a new concept for practical applications of GQDs,revealing the poten-tial of this material for smart applications such as artificial skin,human-machine interfaces,and health monitoring.展开更多
Graphene quantum dots(GQDs)doped InGaO(IGO)thin film transistors(TFTs)have been fabricated based on solution-driven ZrO_(x) as gate dielectrics.Compare to pure IGO TFTs,superior electrical performance of the GQDs-IGO ...Graphene quantum dots(GQDs)doped InGaO(IGO)thin film transistors(TFTs)have been fabricated based on solution-driven ZrO_(x) as gate dielectrics.Compare to pure IGO TFTs,superior electrical performance of the GQDs-IGO TFTs can be achieved by adjusting the doping concentration.It has been demonstrated that GQDs-modified IGO TFTs devices with GQDs doping content of0.3 mg·ml^(-1)have the optimized performances,including field-effect mobility(μ_(FE))of 22.02 cm^(2)·V^(-1)·s^(-1),on/off current ratio(I_(on)/I_(off))of 7.06×10^(7),subthreshold swing(SS)of 0.09 V·dec^(-1),hysteresis of 0.04 V and interfacial trap states(D_(it))of 1.03×10^(12)cm^(-2).In addition,bias stress and illumination stress tests have been performed and excellent stability has been achieved for optimized GQDs-IGO-TFTs.The GQDs-IGO TFTs device showed smaller threshold voltage shift of 0.12 and 0.04 V under positive bias stress(PBS)test and negative bias stress(NBS)test for 3600 s,respectively.And it showed smaller threshold voltage shift of 0.27 and 0.34 V for red light under the PBS and NBS test for 3600 s,respectively.Meanwhile,it showed smaller threshold voltage shift of0.20 and 0.22 V for green light under PBS and NBS test for3600 s,respectively.It also showed smaller threshold voltage shift of 0.17 and 0.12 V for blue under the positive bias illumination stress(PBIS)test and negative bias illumination stress(NBIS)test for 3600 s,respectively.Lowfrequency noise(LFN)characteristics of GQDs-IGO/ZrO_(x)TFTs indicated that the noise source came from the fluctuations in mobility.Finally,a low voltage resistor-loaded unipolar inverter has been built based on GQDs-IGO/ZrO_(x)TFT,demonstrating good dynamic response behavior and a maximum gain of 7.4.These experimental results have suggested that solution-processed GQDs-IGO/ZrO_(x)TFT may envision potential applications in low-cost and large-area electronics.展开更多
Graphene quantum dots(GQDs)have attracted increasing attention due to their favorable optical properties and have been widely used,e.g.,in the biomedical field.However,the properties related to the chemical structure ...Graphene quantum dots(GQDs)have attracted increasing attention due to their favorable optical properties and have been widely used,e.g.,in the biomedical field.However,the properties related to the chemical structure of GQDs,resulting in solventdependent optical properties,still remain unclear.Herein,we present the synthesis of long-wavelength emitting GQDs with a size of about 3.6 nm via a solvothermal method using oxo-functionalized graphene(oxo-G)and p-phenylenediamine as precursors and their structural and surface chemical analysis by transmission electron and atomic force microscopy(TEM;AFM)as well as Fourier-transform infrared,Raman,and X-ray photoelectron spectroscopy(FTIR;Raman;XPS).Subsequently,the influence of solvent polarity and proticity on the optical properties of the as-prepared GQDs bearing–OH,–NH_(2),–COOH and pyridine surface groups was investigated.Based on the results of the absorption and fluorescence(FL)studies,a possible luminescence mechanism is proposed.The observed solvent-induced changes in the spectral position of the FL maximum,FL quantum yield,and FL decay kinetics in protic and aprotic solvents of low and high polarity are ascribed to a combination of polarity effects,intramolecular charge transfer(ICT)processes,and hydrogen bonding.Moreover,the potential of GQDs for the optical sensing of trace amount of water was assessed.The results of our systematic spectroscopic study will promote the rational design of GQDs and shed more light on the FL mechanism of carbon-based fluorescent nanomaterials.展开更多
This work presents solution-processed high-performance graphene quantum dots(GQDs)decorated amor-phous InGaZnO(α-IGZO)thin-film transistors(TFTs)based on ZrO x as gate dielectrics.Compare with pure IGZO TFTs,GQDs-mod...This work presents solution-processed high-performance graphene quantum dots(GQDs)decorated amor-phous InGaZnO(α-IGZO)thin-film transistors(TFTs)based on ZrO x as gate dielectrics.Compare with pure IGZO TFTs,GQDs-modifiedα-IGZO TFTs devices with optimized doping content have demonstrated better performances,including a larger field-effect mobility(μFE)of 35.91 cm 2 V^(-1)s^(-1),a higher on/offcurrent ratio(I ON/I OFF)of 5.04×10^(8),a smaller subthreshold swing(SS)of 0.11 V dec^(-1)and a smaller interfacial trap states(D it,1.57×10^(12)cm^(−2)).Moreover,the GQDs-doped IGZO TFTs with a doping concentration of 0.5 mg ml^(-1)have shown excellent stability under bias stress and illumination stress conditions.To demonstrate the potential applications ofα-IGZO TFTs in logic circuits,a resistor-loaded unipolar inverter based on GQDs-IGZO/ZrO x has been integrated,demonstrating good dynamic behavior and a high gain of 9.3.Low-frequency noise(LFN)characteristics of GQDs-IGZO/ZrO x TFTs have suggested that the fluctua-tions in mobility are the noise source.Based on all the experimental findings,it can be concluded that solution-processed GQDs-IGZO/ZrO x TFT may envision promising applications in optoelectronics.展开更多
基金supported by Key Program (U20A20235) funded by National Natural Science Foundation of Chinathe National Natural Science Foundation of China (52171127, 51974242)+2 种基金Regional Innovation Capability Guidance Program of Shaanxi Provincial Government (2022QFY10-06)Key R&D Program of Xianyang Science and Technology Bureau (2021ZDYF-GY-0029)Doctoral dissertation innovation fund (310-252072201) by Xi’an University of Technology。
文摘The development of lithium-sulfur(Li-S) battery as one of the most attractive energy storage systems among lithium metal batteries is seriously hindered by low sulfur utilization, poor cycle stability and uneven redeposition of Li anode. It is necessary to propose strategies to address the problems as well as improve the electrochemical performance. One of the effective solutions is to improve the sulfiphilicity of sulfur cathode and the lithiophilicity of the Li anode. Herein, we reported that a synergistic functional separator(graphene quantum dots(GQDs)-polyacrylonitrile(PAN) @polypropylene(PP) separator)improved the electrochemical activity of sulfur cathode as well as the stability of Li anode. GQDs induced uniform Li^(+)nucleation and deposition, which slowed down the passivation of Li anode and avoided shortcircuit. Further, three-dimensional network constructed by electrospinning nanofibers and the polar functional groups of GQDs could both effectively inhibit the shuttle of LiPSs and improve the sulfur utilization. The stability of Li-S battery was improved by the synergistic effect. In addition, GQDs and electrospinning nanofibers protector increased lifetime of separators. Benefiting from the unique design strategy, Li//Li symmetric battery with GQDs-PAN@PP separators exhibited stably cycling for over 600 h. More importantly, the Li-S full batteries based GQDs-PAN@PP separators enabled high stability and desirable sulfur electrochemistry, including high reversibility of 558.09 mA h g^(-1)for 200 cycles and durable life with a low fading rate of 0.075% per cycle after 500 cycles at 0.5 C. Moreover, an impressive areal capacity of 3.23 mA h cm^(-2)was maintained under high sulfur loading of 5.10 mg cm^(-2). This work provides a new insight for modification separator to improve the electrochemical performance of Li-S/Li metal batteries.
基金financially supported by the National Nature Science Foundations of China (Nos. 52002157 and 51873083)the Nature Science Foundations of Jiangsu Province, China (No. BK20190976)
文摘Cost-effective,safe,and highly performing energy storage devices require rechargeable batteries,and among various options,aqueous zinc-ion batteries(ZIBs)have shown high promise in this regard.As a cathode material for the aqueous ZIBs,manganese dioxide(MnO_(2))has been found to be promising,but certain drawbacks of this cathode material are slow charge-transfer capability and poor cycling performance.Herein,a novel design of graphene quantum dots(GQDs)integrated with Zn-intercalated MnO_(2)nanosheets is put forward to construct a 3D nanoflower-like GQDs@ZnxMnO_(2)composite cathode for aqueous ZIBs.The synergistic coupling of GQDs modification with Zn intercalation provides abundant active sites and conductive medium to facilitate the ion/electron transmission,as well as ensure the GQDs@ZnxMnO_(2)composite cathode with enhanced charge-transfer capability and high electrochemical reversibility,which are elucidated by experiment results and in-situ Raman investigation.These impressive properties endow the GQDs@ZnxMnO_(2)composite cathode with superior aqueous Zn^(2+) storage capacity(~403.6 mAh·g^(−1)),excellent electrochemical kinetics,and good structural stability.For actual applications,the fabricated aqueous ZIBs can deliver a substantial energy density(226.8 W·h·kg^(−1)),a remarkable power density(650 W·kg^(−1)),and long-term cycle performance,further stimulating their potential application as efficient electrochemical storage devices for various energy-related fields.
文摘Pervaporation desalination by highly hydrophilic materials such as poly(vinyl alcohol)(PVA)based separation membrane is a burgeoning technology of late years.However,the improvement of membrane flux in pervaporation desalination has been a difficult task.Here,a novel hybrid membrane with doped graphene oxide quantum dots(GOQDs)which is rich in hydrophilic groups and small size into the matrix of PVA was prepared to improve the membrane flux.The membranes structures were described by field emission scanning electron microscopy(FESEM),atomic force microscopy(AFM),Fourier transform infrared(FT-IR),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA)and X-ray diffraction(XRD).And more,Water contact angle,swelling degree,and pervaporation properties were carried out to explore the effect of GOQDs in PVA matrix.In addition,GOQDs content in the hybrid membrane,NaCl concentration,and feed temperature were investigated accordingly.Moreover,the hydrogen bonds between PVA chains were weakened by the interaction between GOQDs and PVA chains.Significantly,the hybrid membrane with optimized doped GOQDs content,200 mg·L^(-1),displays a high membrane flux of 17.09 kg·m^(-2)·h^(-1)and the salt rejection is consistently greater than 99.6%.
基金supported by the National Natural Science Foundation of China (grant No. 41172146)National Key Basic Research Program of China (grant No. 2014CB238905)
文摘Coal-based graphene quantum dots(GQDs) were successfully produced via a one-step chemical synthesis from six different coal ranks, from which two superhigh organic sulfur(SHOS) coals were selected as natural S-doped carbon sources for the preparation of S-doped GQDs. The effects of coal properties on coal-based GQDs were analyzed by means of high-resolution transmission electron microscopy(HRTEM), X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, X-ray photoelectron spectroscopy(XPS), ultraviolet-visible(UV-Vis) absorption spectroscopy, and fluorescence emission spectra. It was shown that all coal samples can be used to prepare GQDs, which emit bluegreen and blue fluorescence under ultraviolet light. Anthracite-based GQDs have a hexagonal crystal structure without defects, the largest size, and densely arranged carbon rings in their lamellae; the highrank bituminous coal-based GQDs are relatively reduced in size, with their hexagonal crystal structure being only faintly visible; the low-rank bituminous coal-based GQDs are the smallest, with sparse lattice fringes and visible internal defects. As the metamorphism of raw coals increases, the yield decreases and the fluorescence quantum yield(QY) initially increases and then decreases. Additionally, the surface of GQDs that were prepared using high-rank SHOS coal(high-rank bituminous coal) preserves rich sulfur content even after strong oxidation, which effectively adjusts the bandgap and improves the fluorescence QY. Thus, high-rank bituminous coal with SHOS content can be used as a natural S-doped carbon source to prepare S-doped GQDs, extending the clean utilization of low-grade coal.
基金supported by grants from the Key Program of the National Natural Science Foundation of China(U1432248)the National Natural Science Foundation of China(11305226,11175222)
文摘Objective To evaluate the bio-safety of graphene quantum dots (GQDs), we studied its effects on the embryonic development of zebrafish. Methods In vivo, biodistribution and the developmental toxicity of GQDs were investigated in embryonic zebrafish at exposure concentrations ranging from 12.5-200μg/mL for 4-96 h post-fertilization (hpf). The mortality, hatch rate, malformation, heart rate, GQDs uptake, spontaneous movement, and larval behavior were examined. Results The fluorescence of GQDs was mainly localized in the intestines and heart. As the exposure concentration increased, the hatch and heart rate decreased, accompanied by an increase in mortality. Exposure to a high level of GQDs (200μg/mL) resulted in various embryonic malformations including pericardial edema, vitelline cyst, bent spine, and bent tail. The spontaneous movement significantly decreased after exposure to GQDs at concentrations of 50, 100, and 200μg/mL. The larval behavior testing (visible light test) showed that the total swimming distance and speed decreased dose-dependently. Embryos exposed to 12.5 μg/mL showed hyperactivity while exposure to higher concentrations (25, 50, 100, and 200μg/mL) caused remarkable hypoactivity in the light-dark test. Conclusion Low concentrations of GODs were relatively non-toxic. However, GQDs disrupt the progression of embryonic development at concentrations exceeding 50 μg/mL.
基金supported by the L2CM,UMR 7053,a partner of the Jean Barriol Institute at the Universit e de Lorraine(France)。
文摘Graphene quantum dots(GQDs)which are nanofragments of graphene with an average size between 2 and 50 nm have attracted much attention due to their outstanding properties such as high conductivity,high surface area,and good solubility in various solvents.GQDs combine the quantum confinement and edges effects and the properties of graphene.Therefore,GQDs offers a broad range of applications in various fields(medicine,energy conversion,and energy storage devices).This review will present the recent research based on the introduction of GQDs in batteries,supercapacitors,and microsupercapacitors as electrodes materials or mixed with an active material as an auxiliary agent.Tables,discussed on selected examples,summarize the electrochemical performances and finally,challenges and perspectives are recalled for the subsequent optimization strategy of electrode materials.This review is expected to appeal a broad interest on functional GQDs materials and promote the further development of high-performance energy storage device.
基金financially supported by the National Natural Science Foundation of China (No. 21674011)Beijing Municipal Natural Science Foundation (No. 2172040)
文摘Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB932700 and 2011CB932703)the National Natural Science Foundation of China(Grant Nos.61335006,61378073,and 61077044)the Beijing Natural Science Foundation,China(Grant No.4132031)
文摘We report a facile method of synthesizing graphene quantum dots(GQDs) with tunable emission. The as-prepared GQDs each with a uniform lateral dimension of ca. 6 nm have fine solubility and high stability. The photoluminescence mechanism is further investigated based on the surfacestructure and the photoluminescence behaviors. Based on our discussion, the green fluorescence emission can be attributed to the oxygen functional groups, which could possess broad emission bands within the π –π * gap. This work is helpful to explain the vague fluorescent mechanism of GQDs, and the reported synthetic method is useful to prepare GQDs with controllable fluorescent colors.
基金supported in part by National Natural Science Foundation of China(81202454)Guangdong Province Higher Vocational Colleges and Schools Pearl River Scholar Funded Scheme(2012)Project of Research Development and Industrialization of Guangdong Province(2013B090500046)
文摘Graphene quantum dots(GQDs)are two-dimensional carbon nano-material with excellent physicochemical properties,including biocompatibility,high photoluminescence,water-solubility,hypotoxicity and so on.Owing to bigπ-conjugated structure and oxygen-containing functional groups,GQDs have the ability to absorb various chemical drugs viaπ-πstacking and electrostatic interaction.On the other hand,owning to photoluminescence,GQDs also have potential to serve as fluorescence probe for bioimaging,especially for optical diagnostics.In addition,GQDs have the ability to generate reactive oxygen species(ROS)including singlet oxygen upon photoexcitation.Therefore,GQDs are likely to be used for photodynamic therapy.This article aims to review the frontier researches about GQDs in the field of fluorescence probe,photodynamic therapy and anti-tumor drug delivery system.
基金Funded by the National Natural Science Foundation of China(21676070)the Hebei Training Program for Talent Project(A2015007)+1 种基金the Beijing National Laboratory for Molecular Sciences(20140120)the Special Project for Synthesis and Application of Graphene in Hebei University of Science and Technology(2015PT65)
文摘We demonstrated a facile method to prepare photoluminescent graphene quantum dots using commercial polyacrylonitrile(PAN) based carbon fibers(CFs) as the raw material by facile chemical oxidation and exfoliation method. The as-prepared GQDs with uniform size exhibit an excitation-independent photoluminescence behavior, which is similar to other semiconductor quantum dots. Moreover, when acting as catalyst the uniform GQDs have better activity for electrochemical oxidation of dopamine(DA) than graphene oxides(GOs). The square wave voltammogram(SWV) peak values of GQDs are in good correspondence with DA concentrations and can act as a sensor of DA.
基金supported by the Australian Government Depart-ment of Industry,Innovation,and Science through the Australia-China Science and Research Fund(ACSRF48154)collaboration with the Australia Research Council Research Hub for Energy-efficient Separation(IH 170100009).
文摘Reduced graphene oxide(rGO)membranes have been intensively evaluated for desalination and ionic sieving applications,benefiting from their stable and well-confined interlayer channels.However,rGO membranes generally suffer from low permeability due to the high transport resistance resulting from the narrowed two-dimensional(2D)channels.Although high permeability can be realized by reducing membrane thickness,membrane selectivity normally declines because of the formation of nonselective defects,in particular pinholes.In this study,we demonstrate that the non-selective defects in ultrathin rGO membranes can be effectively minimised by a facile posttreatment via surfacedeposition of graphene quantum dots(GQDs).The resultant GQDs/rGO membranes obtained a good trade-off between water permeance(14 L·m^(-2)·h^(-1).MPa^(-1))and NaCl rejection(91%).This work provides new insights into the design of high quality ultrathin 2D laminar membranes for desalination,molecular/ionic sieving and other separation applications.
基金Project supported by the National Basic Research Program of China(Grant Nos.2016YFA0202300 and 2016YFA0202302)the National Natural Science Foundation of China(Grant Nos.61527817,61335006,and 61378073)the Overseas Expertise Introduction Center for Discipline Innovation,111 Center,China
文摘The substrate treatment with seeding promoter can promote the two-dimensional material lateral growth in chemical vapor deposition (CVD) process. Herein, graphene quantum dots (GQDs) as a novel seeding promoter were used to obtain uniform large-area MoS2 monolayer. The obtained monolayer MoS2 films were confirmed by optical microscope, scanning electron microscope, Raman and photoluminescence spectra. Raman mapping revealed that the MoS2 monolayer was largely homogeneous.
基金Funded by the National Natural Science Foundation of China(Nos.21275063 and 21005029)the Development and Reform Commission of Jilin Province(No.2015Y048)the Youth Science Fund of Jilin Province(20140520081JH)
文摘A modulated photoluminescence nanosensor was developed for the quantitative detection of formaldehyde with nitrogen-doped graphene quantum dots and melamine. The sensing system was based on the different activated effects of melamine and hydrogen peroxide on the photoluminescence intensity of nitrogendoped graphene quantum dots. Under the optimal conditions, the modulated photoluminescence sensing system can be used to detect formaldehyde with a good linear relationship between the nitrogen-doped graphene quantum dots photoluminescence difference and the concentration of formaldehyde. The novel sensing system provided new directions for the detection of formaldehyde with high selectivity and quick response.
基金supported by the National Natural Science Foundation of China (21175043,91233102)the Fundamental Research Funds for the Central Universities for financial support
文摘CdSe quantum dot sensitized solar cells (QDSCs) modified with graphene quantum dots (GQDs) have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage (Voc) of the modified QDSCs was approximately 0.04 V higher than that of plain CdSe QDSCs, consequently improving the photovoltaic performance of the resulting QDSCs. Served as a novel coating on the CdSe QD sensitized photoanode, GQDs played a vital role in improving Voc due to the suppressed charge recombination which has been confirmed by electron impedance spectroscopy as well as transient photovoltage decay measure- ments. Moreover, different adsorption sequences, concentration and deposition time of GQDs have also been systematically investigated to boost the power conversion efficiency (PCE) of CdSe QDSCs. After the coating of CdSe with GQDs, the resulting champion CdSe QDSCs exhibited an improved PCE of 6.59% under AM 1.5G full one sun illumination.
基金the National Natural Science Foundation of China(Grant Nos.61106098,51201150 and 11374250)Key Project of Applied Basic Research of Yunnan Province,China(Grant No.2012FA003)PolyU Grant(1-ZVGH)and Research Grants Council of Hong Kong(Project Nos.PolyU 153030/15P and PolyU 153271/16P).
文摘Zero-dimensional graphene quantum dots(GQDs)exhibit many different properties,such as strong fluorescence,nonzero bandgap and solubility in solvents,compared to two-dimensional graphene.GQDs are biocompatible and have low toxicity;hence,they are widely used in the biomedical field.The edge effect of GQDs is of particular interest because edge modification can regulate the performance of nanomaterials.In this review,various preparation methods for GQDs,which can be divided into three main categories,namely top-down,bottom-up and chemical methods,are discussed.The unique optical,electrical,thermal and magnetic properties of GQDs are reviewed.The functionalization of GQDs by doping with heteroatoms and forming composites with other materials is studied,and the characteristics of these GQDs are also discussed.The applications of these GQDs in the fields of optics,electricity,optoelectronics,biomedicine,energy,agriculture and other emerging interdisciplinary fields are reviewed to highlight the enormous potential of nanomaterials.This review reports on the recent advancement in GQD research and suggests future directions for the development of GQDs.
基金financially supported by the National Natural Science Foundation of China (Nos.U2002212,52102058,52204414,52204413,and 52204412)the National Key R&D Program of China (Nos.2021YFC1910504,2019YFC1907101,2019YFC1907103,and 2017YFB0702304)+7 种基金the Key R&D Program of Ningxia Hui Autonomous Region,China (Nos.2021BEG01003 and2020BCE01001)the Xijiang Innovation and Entrepreneurship Team,China (No.2017A0109004)the Macao Young Scholars Program (No.AM2022024),Chinathe Beijing Natural Science Foundation (Nos.L212020 and 2214073),Chinathe Guangdong Basic and Applied Basic Research Foundation,China (Nos.2021A1515110998 and 2020A1515110408)the China Postdoctoral Science Foundation (No.2022M710349)the Fundamental Research Funds for the Central Universities,China (Nos.FRF-BD-20-24A,FRF-TP-20-031A1,FRF-IC-19-017Z,and 06500141)the Integration of Green Key Process Systems MIIT and Scientific and Technological Innovation Foundation of Foshan,China(Nos.BK22BE001 and BK21BE002)。
文摘Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.
基金support of a Griffith Publication Assis-tance Scholarship(PAS).Q.L.wishes to thank the support from Australian Research Council(Nos.DP160104089,IH 180100002,and DP 200101105).D.C.is grateful for the support of a Griffith Univer-sity New Researcher Grant.The authors are grateful for the support of centre of Microscopy and Microanalysis(CMM)at the University of Queensland for acquiring SEM and TEM images.The authors also thank the Queensland Node of Australian National Fabrication Fa-cility(ANFF)for their assistance in fabrication of photomasks.
文摘Graphene quantum dots(GQDs)refer to graphene fragments with a lateral dimension typically less than 100 nm,which possess unique electrical and optical properties due to the quantum confinement effect.In this study,we demonstrate that chemically derived graphene quantum dots show great potential for making highly stretchable and cost-effective strain sensors via an electron tunneling mechanism.Stretch-able strain sensors are critical devices for the field of flexible or wearable electronics which are expected to maintain function up to high strain values(>30%).However,strain sensors based on conventional materials(i.e.metal or semiconductors)or metal nanoparticles(e.g.gold or silver nanoparticles)only work within a small range of strain(i.e.the former have a working range<1%and the latter<3%).In this study,by simply dropcasting solution-processed GQDs between the interdigitated electrodes on polydimethylsiloxane,we obtained devices that can function in the range from 0.06%to over 50%ten-sile strain with both the sensitivity and working range conveniently adjustable by the concentration of GQDs applied.This study provides a new concept for practical applications of GQDs,revealing the poten-tial of this material for smart applications such as artificial skin,human-machine interfaces,and health monitoring.
基金financially supported by the National Natural Science Foundation of China(No.11774001)Anhui Project(No.Z010118169)Open Fund Project of Zhejiang Engineering Research Center of MEMS in Shaoxing University(No.MEMSZJERC2202)。
文摘Graphene quantum dots(GQDs)doped InGaO(IGO)thin film transistors(TFTs)have been fabricated based on solution-driven ZrO_(x) as gate dielectrics.Compare to pure IGO TFTs,superior electrical performance of the GQDs-IGO TFTs can be achieved by adjusting the doping concentration.It has been demonstrated that GQDs-modified IGO TFTs devices with GQDs doping content of0.3 mg·ml^(-1)have the optimized performances,including field-effect mobility(μ_(FE))of 22.02 cm^(2)·V^(-1)·s^(-1),on/off current ratio(I_(on)/I_(off))of 7.06×10^(7),subthreshold swing(SS)of 0.09 V·dec^(-1),hysteresis of 0.04 V and interfacial trap states(D_(it))of 1.03×10^(12)cm^(-2).In addition,bias stress and illumination stress tests have been performed and excellent stability has been achieved for optimized GQDs-IGO-TFTs.The GQDs-IGO TFTs device showed smaller threshold voltage shift of 0.12 and 0.04 V under positive bias stress(PBS)test and negative bias stress(NBS)test for 3600 s,respectively.And it showed smaller threshold voltage shift of 0.27 and 0.34 V for red light under the PBS and NBS test for 3600 s,respectively.Meanwhile,it showed smaller threshold voltage shift of0.20 and 0.22 V for green light under PBS and NBS test for3600 s,respectively.It also showed smaller threshold voltage shift of 0.17 and 0.12 V for blue under the positive bias illumination stress(PBIS)test and negative bias illumination stress(NBIS)test for 3600 s,respectively.Lowfrequency noise(LFN)characteristics of GQDs-IGO/ZrO_(x)TFTs indicated that the noise source came from the fluctuations in mobility.Finally,a low voltage resistor-loaded unipolar inverter has been built based on GQDs-IGO/ZrO_(x)TFT,demonstrating good dynamic response behavior and a maximum gain of 7.4.These experimental results have suggested that solution-processed GQDs-IGO/ZrO_(x)TFT may envision potential applications in low-cost and large-area electronics.
基金This research is supported by the Deutsche Forschungsgemeinschaft project No.392444269(DFG,German Research Foundation),the China Scholarship Council(CSC)supported by the DFG.C.N.and A.T.acknowledge DFG financial support via the research infrastructure grant INST 275/257-1 FUGG(project No.313713174)+2 种基金funding through ESF Research Groups 2019 FGR 0080“ESTI”and 2020 FGR 0051“GraphSens”as well as BMWi project ZF4817401VS9“TDraCon”Z.H.from Soochow University is acknowledged for conducting TEM measurements.U.R.G and L.S.gratefully acknowledge financial support by the European Metrology Programme for Innovation and Research(EMPIR)as part of the projects 18HLT02“AeroTox”The EMPIR initiative is co-funded by the European Union’s Horizon 2020 research and innovation programme and by the EMPIR participating states.
文摘Graphene quantum dots(GQDs)have attracted increasing attention due to their favorable optical properties and have been widely used,e.g.,in the biomedical field.However,the properties related to the chemical structure of GQDs,resulting in solventdependent optical properties,still remain unclear.Herein,we present the synthesis of long-wavelength emitting GQDs with a size of about 3.6 nm via a solvothermal method using oxo-functionalized graphene(oxo-G)and p-phenylenediamine as precursors and their structural and surface chemical analysis by transmission electron and atomic force microscopy(TEM;AFM)as well as Fourier-transform infrared,Raman,and X-ray photoelectron spectroscopy(FTIR;Raman;XPS).Subsequently,the influence of solvent polarity and proticity on the optical properties of the as-prepared GQDs bearing–OH,–NH_(2),–COOH and pyridine surface groups was investigated.Based on the results of the absorption and fluorescence(FL)studies,a possible luminescence mechanism is proposed.The observed solvent-induced changes in the spectral position of the FL maximum,FL quantum yield,and FL decay kinetics in protic and aprotic solvents of low and high polarity are ascribed to a combination of polarity effects,intramolecular charge transfer(ICT)processes,and hydrogen bonding.Moreover,the potential of GQDs for the optical sensing of trace amount of water was assessed.The results of our systematic spectroscopic study will promote the rational design of GQDs and shed more light on the FL mechanism of carbon-based fluorescent nanomaterials.
基金supported by the National Natural Science Foundation of China(No.11774001)the Anhui Project(No.Z010118169)the Open Fund Project of Zhejiang Engineering Research Center of MEMS in Shaoxing University(No.MEMSZ-JERC2202).
文摘This work presents solution-processed high-performance graphene quantum dots(GQDs)decorated amor-phous InGaZnO(α-IGZO)thin-film transistors(TFTs)based on ZrO x as gate dielectrics.Compare with pure IGZO TFTs,GQDs-modifiedα-IGZO TFTs devices with optimized doping content have demonstrated better performances,including a larger field-effect mobility(μFE)of 35.91 cm 2 V^(-1)s^(-1),a higher on/offcurrent ratio(I ON/I OFF)of 5.04×10^(8),a smaller subthreshold swing(SS)of 0.11 V dec^(-1)and a smaller interfacial trap states(D it,1.57×10^(12)cm^(−2)).Moreover,the GQDs-doped IGZO TFTs with a doping concentration of 0.5 mg ml^(-1)have shown excellent stability under bias stress and illumination stress conditions.To demonstrate the potential applications ofα-IGZO TFTs in logic circuits,a resistor-loaded unipolar inverter based on GQDs-IGZO/ZrO x has been integrated,demonstrating good dynamic behavior and a high gain of 9.3.Low-frequency noise(LFN)characteristics of GQDs-IGZO/ZrO x TFTs have suggested that the fluctua-tions in mobility are the noise source.Based on all the experimental findings,it can be concluded that solution-processed GQDs-IGZO/ZrO x TFT may envision promising applications in optoelectronics.