Carbon Quantum Research Articles

Carbon Quantum Dot/Multiwalled Carbon Nanotube-Based Self-Powered Strain Sensors for Remote Human Motion Detection

Carbon Quantum Dot/Multiwalled Carbon Nanotube-Based Self-Powered Strain Sensors for Remote Human Motion Detection

An ultrafast rechargeable hybrid potassium dual-ion capacitor based on carbon quantum dot@ultrathin carbon film cathode

An ultrafast rechargeable hybrid potassium dual-ion capacitor based on carbon quantum dot@ultrathin carbon film cathode

Carbon quantum dots/carbon-coated SnS2 as a high-performance potassium-ion battery cathode material

Carbon quantum dots/carbon-coated SnS2 as a high-performance potassium-ion battery cathode material

Ti–Cr–N Nanopyramid/Nitrogen-Doped Carbon Quantum Dot/Stainless Steel Mesh as a Flexible Supercapacitor Electrode

Ti–Cr–N Nanopyramid/Nitrogen-Doped Carbon Quantum Dot/Stainless Steel Mesh as a Flexible Supercapacitor Electrode

Dual-functional membranes of CQDs/TiO2 @PI/PES nanofibers for the high filter efficiency of ultrafine particles and photocatalytic activity

The carbon quantum dot/titanium dioxide (CQDs/TiO2), fabricated on highly porous polyimide (PI)/polyether sulfone (PES) nanofiber via electrospinning process, called the dual-functional CQD/TiO2 @PI/PES membrane, was developed and evaluated for its performance, including both removal of volatile organic compounds (VOCs) and ultrafine particulate matters (PM0.1). The photocatalytic activity of synthesized CQD/TiO2 @PI/PES membranes with 5% CQD loading on the decomposition of acetone was significantly enhanced compared with that of TiO2(P25)@PI/PES. The comprehensive results of photoluminescence emission, X-ray photoelectron spectroscopy, and photocatalytic experiments suggest that up-conversion properties of CQD can enhance the absorption of visible light on TiO2 and reduce the reorganization of electron-hole pairs. Further, the optimized CQD/TiO2 @PI/PES membrane could effectively photodegrade of acetone (>94.5%) and also maintained a good PM0.1 filtration efficiency (> 99%) and a differential pressure of 0.34 Pa for creating level 3 medical face masks as per the standards of ASTM F2299 and EN 14683. Therefore, the dual-functional CQD/TiO2 @PI/PES membrane could be applied as a promising photocatalytic filter for air purification that simultaneously and remarkably filters PM0.1 and decompose VOCs.

Designing continuous proton-conductive channels for direct methanol fuel cell through the sulfonated poly(ether ether ketone)/carbon quantum dot/graphitic carbon nitride nanosheet

In this research, new nanocomposite membranes were fabricated based on sulfonated poly(ether ether ketone)/carbon quantum dot/graphitic carbon nitride nanosheet (SPEEK/CQD/g-C3N4). It was found that anchoring CQD onto g-C3N4 provides a new proton transport pathway in the design of proton exchange membranes for high-performance fuel cell applications. The uniform distribution of CQDs on the nanosheets and the interaction of hydrophilic groups such as the –NH2 and CO with the -SO3H of the polymer matrix creates a hydrogen bond transfer network and facilitates the protons transfer based on the Grotthuss mechanism. The incorporation of CQD/g-C3N4 in the polymer matrix has increased the proton conduction from 0.023 S/cm for SPEEK at 20 °C and 100 % R.H. to 0.052 S/cm for the SPEEK/CQD/g-C3N4-3 %wt. The proton conduction for the nanocomposite membrane containing 3 wt% CQD/g-C3N4 improved at higher temperatures (0.128 S/cm at 80 °C) and also, this membrane showed better thermal properties (maximum Tg at 176 °C). Compared to the SPEEK membrane, the nanocomposite membrane with 3 wt% CQD/g-C3N4 had a better single-cell direct methanol fuel cell (DMFC) test performance.

Effective peroxydisulfate activation by CQDs-MnFe2O4@ZIF-8 catalyst for complementary degradation of bisphenol A by free radicals and non-radical pathways

The present study reported fabrication of novel carbon quantum dots-MnFe2O4@ZIF-8 (CQDs-MFO@ZIF-8) by using co-precipitation hydrothermal method for activation of peroxydisulfate (PDS) to degrade bisphenol A (BPA), one of important emerging organic pollutants in water environment. CQDs-MFO@ZIF-8 served as a highly efficient thermal activated PDS catalyst with high catalytic degradation efficiency, reusability and stability. The catalyst achieved almost completely removal of 20.0 mg/L BPA within 5.0 min, and the degradation efficiency remained higher than 83% after 5 consecutive cycles. Free radicals (•OH, SO4•− and •O2−) and non-free radicals (1O2) were generated in the thermal PDS-activation system, in which singlet oxygen (1O2) played a dominant role in the degradation of BPA. The potential toxicity of BPA degradation intermediates was analyzed upon the culture of E. coli and Chlorella sorokiniana by using Ecological Structure-Activity Relationship Model (ECOSAR) program. The catalytic performances of BPA degradation by CQDs-MFO@ZIF-8 were evaluated for treatment of different practical water samples to further verify the feasibility of practical applications. This study provides proof-in-concept demonstration of new nanomaterials for enhanced catalytic water decontamination.

Carbon quantum dots/cobalt chalcogenide porous nanofibers for highly efficient electrocatalytic hydrogen evolution

Hydrogen is increasingly needed as a clean energy source with high energy density. Hydrogen evolution reaction (HER) via electrocatalysis is a viable way to produce clean hydrogen. The key to achieving active HER is to select highly-active electrocatalysts. Although Pt-based noble metal catalysts have excellent performance, they are expensive and earth-abundant. Compared to noble metals, cobalt chalcogenide has been used for efficient HER. Here, we first demonstrated a porous material based on C-dots/cobalt chalcogenide nanofibers as an effective electrocatalyst for HER. Co3O4/10 wt% C-dots nanofibers-based electrode reached an overpotential of 383 mV at the current density of 10 mA·cm−2 with Tafel slope of 93.4 mV·dec−1 in 1 M KOH, which is much better than bare Co3O4 (758 mV at 10 mA·cm−2, Tafel slope is 111.3 mV·dec−1). In addition to the excellent HER performance, the Co3O4/C-dots nanofibers performed very well in terms of stability after a 10-hour operation, and the overpotential was even reduced by 6.7%. With the further sulphuration, the Co3S4/C-dots nanofibers exhibited an overpotential of 280.2 mV at the current density of 10 mA·cm−2. This work indicates that the C-dots can be used as an efficient additive for cobalt chalcogenide based electrocatalysts.

Carbon dots-based dual-emission proportional fluorescence sensor for ultra-sensitive visual detection of mercury ions in natural water

Carbon dots (CDs) have become a hot topic in fluorescence sensing and bioimaging due to their superior optical properties, high sensitivity, and high selectivity for specific ubstances. In this experiment, a novel carbon quantum dot/copper nanocluster dual fluorescence emission composite (CQDs@SiO2/CuNCs) based on silica coating was constructed by a composite of CQDs@SiO2 and DPA-CuNCs, which can detect Hg2+ in water by the change of fluorescence color under UV light. Its detection limit for Hg2+ in aqueous solution is as low as 1 μM. In addition, CQDs@SiO2/CuNCs dual fluorescence emission composites successfully achieved the specific detection of Hg2+ in water samples from the South Lake of Changchun City. Compared with the traditional detection methods, this fluorescent composite has the advantages of convenience and long-term stability, and is more suitable for the rapid detection of mercury ions in the environment, which increases the practical application capability of fluorescent nanocomposites.

Rational construction of metal‑free carbon quantum dots/graphitic carbon nitride composite photocatalyst for mitigation of organic containments

Rational construction of metal‑free carbon quantum dots/graphitic carbon nitride composite photocatalyst for mitigation of organic containments

Achieving efficient incorporation of electron-withdrawing sites into carbon nitride nanosheets for boosting hydrogen generation

There is an acute demand for the development of high-performance photocatalysts for large-scale green H2 production using solar energy. To address this challenge, a novel approach has been proposed for the fabrication of high-performance 0D/2D carbon quantum dot/C3N4 nanosheet heterojunction (CQD/CNN) photocatalytic materials using a tandem synthesis strategy of carboxylated CQD-induced hydrothermal-pyrolysis. The incorporation of CQD into the synthesis of CNN significantly reduces its thickness, making the CQD/CNN low to 2.5 nm, which is a noteworthy one thirty-sixth in height of bulk CNN. The carboxylated CQD play a crucial role in regulating the proportion of oxygen-containing surface functional groups of CQD/CNN. The CQD/CNN heterojunction shows exceptional H2 production rates and demonstrated the ability to convert O2 into H2O2. The H2 production rate of CQD/CNN is gained to be 54.50 mmol g−1 under continuous 3.5 h visible light irradiation, which is a remarkable seven-fold enhancement in performance over bulk CNN. Moreover, the CQD/CNN photocatalyst achieves a maximum H2O2 concentration of 0.763 mmol/L, which is sixteen times higher than that of pure CNN (0.0475 mmol/L). Through elucidating the relationships between morphological/structural modulation and photocatalytic capability, the CO/C–O ratio is found to have the greatest impact on performance, indicating that the electron-withdrawing sites of CQD/CNN can be augmented by incorporating carboxylated CQD, and the electron-withdrawing group can enhance electron conduction and make electron transfer easier to occur, thereby improving the performance of the heterojunctions. Our findings provide a comprehensive framework for achieving desirable photocatalytic properties of C3N4 materials through electron-withdrawing functional group regulation.

Enhancement of color rendering index of stable lead-free perovskite WLEDs through incorporating green carbon dots

In this work, the carbon quantum dots@Cs2NaInCl6 (CDs@CNC) composites are presented by a facile solution synthesis. The obtained CDs@CNC composites maintain the octahedral morphology of original CNC host and the characteristic functional groups of original CDs. As a result, the rare-earth-free CDs@CNC composites exhibit green light emission with good stability for UV irradiation, heat, and humidity. In addition, CDs were combined with ion-doped CNC to obtain multicolor phosphor and the corresponding white light emitting diode (WLED) devices were fabricated by coating composites on commercial UV chips. The color render index (CRI) of WLEDs increases significantly from 66.24 to 90.95 while the cold-warm white fluorescence can be flexibly tuned by the change of excitation wavelength. The combination of CDs and double perovskites provide a new route to design white light emission phosphors, which could lead to the fabrication of next generation high-quality lighting devices.

Carbon quantum dots@metal–organic framework based catalytic nucleic acid fluorescent system for highly sensitive and selective detection of Pb2+ in aqueous solutions

Accumulation of heavy metal ions in the ecosystem has become a major concern due to their adverse impacts on animals, humans, and aquatic habitats. The development of a rapid and portable sensing system is important for the prompt detection and proper management of such pollutants. Herein, we have designed a fluorescence-based biosensor for the selective and sensitive detection of Pb2+ ions using a DNAzyme system that is active only in the presence of lead (II) ions (Pb2+). The developed nanoprobe relies on two major components: (i) boron and nitrogen carbon dots (BNCDs)-doped carboxyl functionalized-terbium metal-organic framework (COOH-Tb MOF) as a fluorescent tag and (ii) quencher-modified catalytic NH3-GR5 DNAzyme as a bioreceptor molecule. The fluorescent tag (BNCDs/MOF) exhibits dual fluorescence with emission peaks located in the regions of blue and green. In the absence of Pb2+ ions, this hybridization undergoes reduced emission intensity because of the overlap in fluorescence emission between BNCDs@Tb-MOF and quenchers. However, as the catalytic core of the DNAzyme strand is activated in the presence of Pb2+ ions, the fluorescent emission of BNCDs/Tb-MOF resumes with the cleavage of quencher-tagged substrate strand. Here, the release of a shorter oligo sequence effectively increases the intensity of the proposed novel biosensor to realize low level detection of Pb2+ (e.g., to 0.96 ppb in a wide detection range from 2 to 1000 nM). The establishment of this novel biosensing approach is expected to offer new insights into rapid, selective, and sensitive detection of major pollutants for food and environmental safety.

Sensitive and selective neurotransmitter epinephrine detection at a carbon quantum dots/copper oxide nanocomposite

Herein, the electrochemical detection of epinephrine (EP) at a carbon quantum dots/copper oxide nanocomposite (CQDs/CuO) modified glassy carbon electrode (GCE) was investigated. The carbon quantum dots (CQDs), copper oxide nanoparticles (CuO NPs), and their composite (CQDs/CuO) were characterized using scanning electron microscopy (SEM), Fourier-Transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, X-ray diffraction (XRD) spectroscopy, Transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). A limit of detection (LoD) of 15.99 µM over a linear dynamic range (LDR) of 10–100 µM was obtained at GCE/CQDs/CuO using the square wave voltammetry (SWV) for EP electroanalysis at pH 7. The theoretical evidence for the conventional weak epinephrinequinone (EPQ) reduction peak and EPQ cyclization was investigated using the density functional theory (DFT) calculations. This sensor was also applied for the analysis of EP in chicken blood serum and EP injection with percentage recovery of 101.23 and 93.54 %, respectively. In addition to its outstanding long-term stability, good reproducibility, and ease of fabrication, the detection of EP in the presence of ascorbic acid (AA) was achieved at this sensor. The proposed sensor also demonstrated the ability to simultaneously detect epinephrine (EP), dopamine (DA), and uric acid (UA).

Encapsulation carbon QDs in In-MIL-68 to derive carbon QDs@In2S3 tube for photoreduction of Cr(VI)

In this work, carbon quantum dots@In2S3 hollow tube (CQDs@In2S3) with sheet-like hierarchical structure was synthesized by sulfidation CQDs@In-MIL-68. The CQDs@In2S3-2 exhibited the optimal Cr(VI) reductive ratio of nearly 100% after 45 ​min light irradiation in solution with pH of 4. The enhanced Cr(VI) reduction activity was ascribed to the efficient separation of electrons and holes after coupling of CQDs. The ·O2− was the dominant active specie to reduce Cr(VI), and possible mechanism was proposed. This work provides thought for design of high-performance photocatalysts by loading electron-collecting species to remove environmental pollutants.

Assay of inorganic pyrophosphatase activity based on a fluorescence “turn–off” strategy using carbon quantum dots@Cu-MOF nanotubes

A highly sensitive and selective sensor for the quantitative assay of inorganic pyrophosphatase (PPase) activity was developed based on a fluorescence “turn–off” strategy. Carbon quantum dots@Cu(II)-based metal–organic framework nanotubes (CQDs@Cu-MOF) with length less than 300 nm and width less than 20 nm were synthesized. CQDs in the nanotubes exhibited weak fluorescence owing to static quenching. The coordination reaction between pyrophosphate ion (PPi) and Cu(II) decomposed CQDs@Cu-MOF and led to the release of CQDs, of which the fluorescence recovered. In the presence of PPase, the hydrolysis of PPi generated phosphate ion (Pi). CQDs@Cu-MOF remained their structural stability and the fluorescence turned off. The fluorescence intensity difference of the mixture of CQDs@Cu-MOF and PPi in the absence and presence of PPase (-ΔF) was proportional to the PPase concentration from 0.1 to 5 mU mL−1 and that from 5 to 50 mU mL−1, and a limit of detection at 0.03 mU mL−1 was obtained. PPase activity in human serum was analyzed using the proposed fluorescence sensor and the recovery values were found to vary from 95.0% to 104 %.

An Electrochemical Sensor Based on Molecularly‐Imprinted‐Polymer‐Modified Carbon Quantum Dots@hexagonal Boron Nitride Nanosheets Nanocomposites for Triclosan Determination

AbstractAn electrochemical sensor based on carbon quantum dots@hexagonal boron nitride nanosheets nanocomposites (CQDs@HBNNS‐NCs) and molecularly imprinted polymer (MIP) was proposed for the triclosan (TCS) analysis. The CQDs@HBNNS‐NCs were utilized as the modifier, which exhibited excellent electrochemical properties. The MIP film was prepared in situ in the presence of template (TCS) and monomer (o‐phenylenediamine) to provide the specific molecular recognition. The CQDs@HBNNS‐NCs were characterized by transmission electron microscopy (TEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the current response was linear with the logarithmic value of TCS concentration in the range of 2 nM–0.1 mM, and the limit of detection (LOD) was calculated as 0.005 μM (S/N=3). Furthermore, the proposed electrochemical sensor showed favorable selectivity, stability, and was used for the TCS analysis in tap water samples with decent accuracy.

An electrochemical aptasensor for detection of prostate-specific antigen-based on carbon quantum dots-gold nanoparticles.

In this work, an electrochemical aptasensor was described for the determination of prostate-specific antigen (PSA). Aptamer chains were decorated on the surface of a glassy carbon electrode (GCE) via carbon quantum dots/Au nanoparticles (Au/CQD). Structural analysis that was used to characterize the prepared materials shows that Au/CQD nanoparticles synthesized in a spherical shape with an average size of 70 nm. Furthermore, the combination of Au nanoparticles with CQD resulted in formation of crystalline the structure of the Au/CQD composite. To study the electrochemical performance of the prepared aptasensor, cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy were used. The results show that the aptasensor has a good selectivity to PSA over other biomaterials with the time optimized about 30 min. K4 [Fe(CN)6 ] was used as an electrochemical probe with the limit of detection about 2 fg⋅mL-1 . To avoid the hazardous nature of K4 [Fe(CN)6 ], a label-based aptasensor was prepared using methylene blue as an electrochemical signal producer. They provide the capability of electrochemical detection in buffer phosphate solution with high sensitivity.

Steady‐State and Dynamic Bioanalysis using Carbon Quantum Dot‐based Luminescence Probes

AbstractCarbon quantum dots (CQDs) with excellent biocompatibility, tunable emission and designable surface composition have been widely applied for luminescent sensing of diverse biological targets. In addition to homogeneous bioanalysis, dynamic bioanalysis of biological analytes is also achieved with the combination of single‐particle imaging technique. In this review, we majorly conclude the recently adopted steady‐state and dynamic bioanalysis based on CQD luminescence probes. The synthesis and luminescence mechanism of CQDs is first introduced. Regarding the CQD‐based luminescent bioanalysis, sensing principles and tactics are provided. The steady‐state bioanalysis systems are discussed according to the targets. Dynamic bioanalysis platforms are concluded in two aspects: time‐dependent accumulation and real‐time dynamics. This review ends with the discussion of challenges and future trends of CQD probe‐based luminescent bioanalysis.

Activated Carbon and Carbon Quantum Dots/Titanium Dioxide Composite Based on Waste Rice Noodles: Simultaneous Synthesis and Application in Water Pollution Control.

To achieve the full utilization of waste rice noodle (WRN) without secondary pollution, activated carbon (AC) and carbon quantum dots/titanium dioxide (CQDs/TiO2) composite were simultaneously synthesized by using WRN as raw material. Both of the two materials showed potential applications in water pollution control. The AC based on WRN displayed a porous spherical micro-morphology, which could absorb heavy metal elements like Pb(II) and Cr(VI) efficiently, with a maximum equilibrium uptake of 12.08 mg·g−1 for Pb(II) and 9.36 mg·g−1 for Cr(VI), respectively. The adsorption of the resulted AC could match the Freundlich adsorption isotherm and the pseudo-second-order kinetics mode. On the other hand, the CQDs/TiO2 composite based on WRN displayed a high efficient photocatalytic degradation effect on various water-soluble dyes such as methylene blue, malachite green, methyl violet, basic fuchsin, and rhodamine B under visible light irradiation, which showed better photocatalytic performance than commercial TiO2. The introduction of CQDs based on WRN to TiO2 could result in efficient electron-hole pair separation and enable more photogenerated electrons to reduce O2 and more photogenerated holes to oxidize H2O or OH−, which could cause stronger abilities in producing O2·− and ·OH radical and better photocatalytic activity.