Fabrication Of Carbon Quantum Dots Research Articles

Green Synthesis of Various Heteroatom‐doped Carbon Quantum Dots from Urine, Whey, and Their Mixture: The Optimization of Synthesis and Potential Applications

AbstractThe employment of biomass waste for the fabrication of carbon quantum dots (CQDs), as a novel fluorescent material with high photoluminescence (PL) activity, has gained intense interest for the last decade. However, the fabrication of CQD from biomass waste encounters challenges including low fluorescence yield, reproducibility, and stability. Therefore, the novel, simple, flexible fabrication routes for CQDs using biomass waste as a precursor are still essential for practical applications. In this study, we reported the employment of human urine (U), sour whey (W), and their mixture (U/W) as precursors for the hydrothermal green synthesis approach. For all cases, CQDs with an excitation‐dependent emission nature were obtained with a quantum yield (QY) value of 48 %, 28 %, and 39 % for U, W, and U/W, respectively. For each case, doping of various heteroatoms such as N, P, S, etc., in the structure of CQDs contributed PL characteristics with high QY, reasonably low cytotoxicity, and, robust pH and storage stability which indicate their high potential in various biomedical applications such as bioimaging and pH sensors. This study proves the utilization of human urine and whey as the precursors for the fabrication of CQDs through a low‐cost, flexible, and eco‐friendly green synthesis procedure.

Fabricating carbon quantum dots of graphitic carbon nitride vis ultrasonic exfoliation for highly efficient H2O2 production

A promising and sustainable approach for producing hydrogen peroxide is the two-electron oxygen reduction reaction (2e– ORR), which uses very stable graphitic carbon nitride (g-C3N4). However, the catalytic performance of pristine g-C3N4 is still far from satisfactory. Here, we demonstrate for the first time the controlled fabrication of carbon quantum dots (CQDs)-modified graphitic carbon nitride carbon (g-C3N4/CQDs-X) by ultrasonic stripping for efficient 2e– ORR electrocatalysis. HRTEM, UV–vis, EPR and EIS analyses are in good consistent which prove the in-situ generation of CQDs. The effect of sonication time on the physical properties and ORR activity of g-C3N4 is discussed for the first time. The g-C3N4/CQDs-12 catalyst shows a selectivity of up to 95% at a potential of 0.35 V vs. RHE, which is much higher than that of the original g-C3N4 catalyst (88%). Additionally, the H2O2 yield is up to 1466.6 mmol g−1 in 12 h, which is twice as high as the original g-C3N4 catalyst. It is discovered that the addition of CQDs through ultrasonic improves the g-C3N4 catalyst's electrical conductivity and electron transfer capability in addition to its high specific surface area and distinctive porous structure, speeding up the reaction rate. This research offers a green method for enhancing g-C3N4 activity.

Fabrication of carbon quantum dots modulated/polyindole(PIn/CDs) thin film by electrospray deposition for high-performance next-generation solid-state supercapacitor

A binder-free polyindole/carbon quantum dots (PIn/CDs) thin-film/layer electrode is synthesized by a hybrid-electrospray method. The synthesized CDs and PIn/CDs samples are used for furthercharacterization. Owing to the synergistic consequence of PIn and CDs, PIn/CDs display outstanding electrochemicalassets and cyclability, whichare deserved from the presence of robust interactions amongst polymeric chains and CDs. Further, CDs offer an electron allocation pathway owing to their extraordinary electricconductivity and high specific surface area. In a 3 M KOH aqueous-electrolyte, the Qs of PCDs-2is394 C/g at 6 A/g, which is higher than other comparative electrodes. The PCDs-2 film shows excellent cyclicretention of 75% at 20 Ag−1 up to 3000 cycles. The fabricated PIn/CDs-2//rGO asymmetric device shows the highest specific capacity of 54.5 C/g at 1 A/g with theenergy and power density of 15.9 Wh/kg and 955.6 W/kg. Theseresults demonstrate that PIn/CDs thin-film could be used as an efficient electrode for supercapacitor application.

Simple fabrication of carbon quantum dots and activated carbon from waste wolfberry stems for detection and adsorption of copper ion.

Removal of heavy metal pollution is an endless topic, because heavy metals can cause irreversible damage to the human body and environment. It is urgent to develop novel materials for detection and adsorption of heavy metal ions. In this paper, waste wolfberry straw was utilized as a carbon source, and two simple methods were developed to successfully prepare activated carbon (AC) and carbon quantum dots (CQDs). The fabrication conditions were optimized by adjusting the mass ratio of precursor to activator, type of activator and activation times. When sodium hydroxide (NaOH) was selected as an activator (6 : 1, mass ratio of NaOH to AC-precursor), and the activation was performed at 600 °C for 1 h, the highest specific surface area of the obtained AC-NaOH-3 reached 3016 m2 g-1. The adsorption capacity for copper ions (Cu2+) reached 68.06 mg g-1. The preparation conditions for CQDs were also optimized by adjusting the concentration of wolfberry stem, reaction time and temperature. When the wolfberry stem concentration was 7.5 g L-1, and the activation was performed at 200 °C for 24 h, the obtained CQDs exhibited strong fluorescence emission in the blank and 12 kinds of metal ion solutions, respectively, however, the fluorescence intensity was remarkably decreased after adding Cu2+. In the range of 10-80 nM, the linear correlation coefficient between the concentration of Cu2+ and fluorescence intensity of CQDs was 0.992, and the limit of detection was 2.83 nmol L-1. Thus, these two kinds of materials were prepared from wolfberry stem, which opened up a new way for the application in adsorption and detection of copper ions.

Green synthesized carbon quantum dot as dual sensor for Fe(II) ions and rational design of catalyst for visible light mediated abatement of pollutants

Herein we report the fabrication of carbon quantum dots through a green, cost-effective, and one-pot method from Wrightia tinctoria leaves. The CQDs are effective as fluorescent and electrochemical sensors for Fe(II) ions, with a detection limit of 2.3 nM. In the presence of Fe(II), strongly fluorescent quenching of CQDs occurred, providing the basis of Fe(II) quantification. The versatile sensing ability of CQDs in various real samples indicates the significant potential of carbon-based materials in developing sensing platforms for accurate and fast assay of different analytes. The synthesized green carbon dots and Bi4O5Br2 were fabricated on ZrO2 nanoparticles using a simple approach to create a high-efficiency ZrO2/CQD/Bi4O5Br2 photocatalyst composite to degrade contaminants. The fabricated CQD-based nanocomposite successfully degraded rhodamine B. The catalyst composition was optimized by varying Bi4O5Br2 content, and the ZrO2/CQD/Bi4O5Br2 (15 %) showed enhanced degradation efficiency and followed pseudo-first-order kinetics. More than 95 % of degradation efficiency in a short period and enhanced stability promise the nanocomposite's future industrial applications. This offers a novel approach to developing green carbon dots as a sensor for metal ions and its modified composites as visible-light-induced photocatalysts for the effective degradation of contaminants.

State-of-the-art developments in carbon quantum dots (CQDs): Photo-catalysis, bio-imaging, and bio-sensing applications.

Carbon quantum dots (CQDs), the intensifying nanostructured form of carbon material, have exhibited incredible impetus in several research fields such as bio-imaging, bio-sensing, drug delivery systems, optoelectronics, photovoltaics, and photocatalysis, thanks to their exceptional properties. The CQDs show extensive photonic and electronic properties, as well as their light-collecting, tunable photoluminescence, remarkable up-converted photoluminescence, and photo-induced transfer of electrons were widely studied. These properties have great advantages in a variety of visible-light-induced catalytic applications for the purpose of fully utilizing the energy from the solar spectrum. The major purpose of this review is to validate current improvements in the fabrication of CQDs, characteristics, and visible-light-induced catalytic applications, with a focus on CQDs multiple functions in photo-redox processes. We also examine the problems and future directions of CQD-based nanostructured materials in this growing research field, with an eye toward establishing a decisive role for CQDs in photocatalysis, bio-imaging, and bio-sensing applications that are enormously effective and stable over time. In the end, a look forward to future developments is presented, with a view to overcoming challenges and encouraging further research into this promising field.

Fabrication of carbon quantum dots via ball milling and their application to bioimaging

Carbon quantum dots (CQDs) with an average diameter of 3 nm, exhibiting blue photoluminescence, have been obtained from commercial conductive carbon black by a cost-effective and straightforward exfoliation method using dry ball milling in the presence of sodium carbonate. As a secondary abrasive medium, sodium carbonate provides effective exfoliation of carbon black with a high degree of CQD graphitization and plays an essential role in the functionalization of CQDs with oxygen groups. Due to the low toxicity of CQDs against HeLa cancer cells (cell viability above 90% at a CQD concentration of 200 μg cm−3) and the ability to penetrate cells and emit blue light, CQDs are possibly suitable for biological imaging of cells.

Facile synthesis of B,N-doped CQDs as versatile fluorescence probes for sensitive detection of cobalt ions in environmental water and biological samples

Fabrication of carbon quantum dots (CQDs) as versatile fluorescence probes for simultaneous detection of cobalt ion (Co2+) in various samples is still unmet. Herein, novel boron, nitrogen-doped carbon quantum dots (B,N-CQDs) were facile synthesized via one-step hydrothermal method, in which 3-carboxyphenylboronic acid and ethylenediamine were selected as precursors. Owing to the unique properties of the precursors, the obtained B,N-CQDs exhibited excellent recognition capability of Co2+, favorable biocompatibility, and high fluorescence quantum yield (FLQY, 64.8%), which enabled the B,N-CQDs as versatile fluorescence probes for sensitive detection of Co2+. The response of the probes to Co2+ was linear in two ranges of 0.5–10 and 10–2000 nM with limit of detection (LOD) of 0.52 nM. Feasibility of practical application of the probes was assessed by quantitative detection of trace Co2+ in real water samples including sewage water, river water and tap water. Furthermore, Co2+ in human urine was detected by using the probes with recoveries between 96% and 104%, indicating that the established probes could meet the requirements of practical detection in urine samples. Besides, the probes were successfully applied to monitoring Co2+ in A549 cells via fluorescence imaging attributed to their excellent photostability and high signal-to-background ratio. All these results show that the designed B,N-CQDs are ideal probes for simultaneously detecting Co2+ in environmental water and biological samples, which would expand the practical application of CQDs.

Facial fabrication of carbon quantum dots (CDs)-modified N-TiO2-x nanocomposite for the efficient photoreduction of Cr(VI) under visible light

In this study, for the first time, a novel CDs-N-TiO2-x nanocomposite was successfully fabricated by decorating the carbon quantum dots (CDs) on the nitrogen (N) and Ti3+ codoped TiO2 nanoparticles using a facile hydrothermal-calcination method. X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS), electron paramagnetic resonance (EPR) spectra, and X-ray photoelectron spectroscopy (XPS), etc., were utilized to investigate the physicochemical properties of the catalyst and to confirm the successful introduction of CDs and the formation of N/Ti3+ codoping levels in the nanocomposite. Owing to the synergy between the modification of CDs and codoping of N and Ti3+, the as-prepared CDs-N-TiO2-x nanocomposite exhibited enhanced visible light absorption and more efficient charge separation compared with its counterparts, such as the pristine TiO2, N-doped TiO2 (N-TiO2), N and Ti3+ codoped TiO2 (N-TiO2-x), and carbon quantum dots-TiO2 (CDs-TiO2), etc. As a result, the CDs-N-TiO2-x nanocomposite displayed a remarkable performance for Cr(VI) reduction under visible light irradiation. Moreover, adding the appropriate amount of citric acid as the hole scavenger significantly increased the reduction rate of Cr(VI). In addition, the reduction efficiency was better under acidic conditions and considerably affected by the initial Cr(VI) concentration and catalyst dosage. Thermogravimetric analysis and cyclic runs demonstrated a unique thermal and chemical stability of the CDs-N-TiO2-x nanocomposite. The mechanism of the enhanced photoreduction of Cr(VI) by the CDs-N-TiO2-x nanocomposite was discussed based on all the characterization and experimental results. Moreover, the developed CDs-N-TiO2-x nanocomposite also exhibited efficient photocatalytic performance to reduce the Cr(VI) contained in real laboratory wastewater.

Carbon Quantum Dots/Bi2WO6 Composites for Efficient Photocatalytic Pollutant Degradation and Hydrogen Evolution

In this study, we report the facile fabrication of carbon quantum dots (CQDs)/Bi2WO6 nanocomposites, as well as their effective photocatalytic activity for the photodegradation of organic pollutants and hydrogen production. The observed results here revealed that CQDs/Bi2WO6 composites possessed much higher photocatalytic activity in the degradation of both rhodamine B and phenol under simulated solar light after optimizing the hybridization with CQDs, which was attributed to the excellent up-converted photoluminescence, photo-induced electron transfer and electron reservoir properties of CQDs. Significantly different from pure Bi2WO6, the CQDs/Bi2WO6 composites also displayed excellent photocatalytic H2 production activity, which can be ascribed to the suitable conduction band edge and sufficient reduction ability of CQDs.

Fabrication of carbon quantum dots with nano-defined position and pattern in one step via sugar-electron-beam writing.

Quantum dots (QDs) are promising materials in nanophotonics, biological imaging, and even quantum computing. Precise positioning and patterning of QDs is a prerequisite for realizing their actual applications. Contrary to the traditional two discrete steps of fabricating and positioning QDs, herein, a novel sugar-electron-beam writing (SEW) method is reported for producing QDs via electron-beam lithography (EBL) that uses a carefully chosen synthetic resist, poly(2-(methacrylamido)glucopyranose) (PMAG). Carbon QDs (CQDs) could be fabricated in situ through electron beam exposure, and the nanoscale position and luminescence intensity of the produced CQDs could be precisely controlled without the assistance of any other fluorescent matter. We have demonstrated that upon combining an electron beam with a glycopolymer, in situ production of CQDs occurs at the electron beam spot center with nanoscale precision at any place and with any patterns, an advancement that we believe will stimulate innovations in future applications.

Rapid fabrication of carbon quantum dots as multifunctional nanovehicles for dual-modal targeted imaging and chemotherapy.

In this manuscript, we reported a facial, rapid, and environmental friendly method to fabricate hetero atoms including gadolinium, nitrogen, and sulfur doped multi-functional magnetofluorescent carbon quantum dots (GdNS@CQDs) nanocomposite. These multifunctional GdNS@CQDs were conjugated with a folic acid for targeting dual modal fluorescence/magnetic resonance imaging. Additionally, an anticancer drug, doxorubicin, was incorporated into the nanocomposite forming FA-GdNS@CQDs-DOX, which enables targeted drug delivery. We have developed GdNS@CQDs with integrated functions for simultaneous in vitro cell imaging, targeting, and pH-sensitive controlled drug release in HeLa cells. Furthermore, we successfully demonstrated the use of this material for in vivo fluorescence imaging, using zebrafish as an animal model.

Fabrication of carbon quantum dots modified granular SnO2 nanotubes for visible light photocatalysis

The C QDs modified granular SnO2 nanotubes are prepared via a simple technical route through which SnO2 nanotubes are dispersed in C QDs solution, then dried at 80°C. The results of X-ray photoelectron spectroscopy, Fourier-transform infra-red spectroscopy, transmission electron microscopy indicated that SnO2 nanotubes are well combined with C QDs through surface carbon–oxygen groups. By degradation of Rhodamine B under visible light irradiation, it demonstrates that the photocatalytic performance of these composites significantly enhanced. Furthermore, the unique up-converted photoluminescence behaviour of the carbon dots and the remarkable granular, tube-shape structure of the SnO2 are considered as the main reasons of this enhancement.

Fabrication of carbon quantum dots and their application for efficient detecting Ru(bpy)32+ in the solution

Carbon quantum dots (CDs) with an average size of less than 10nm were prepared by ionic liquid-assisted electrochemical exfoliation of graphite electrode, and developed as photoluminescence (PL) and electrochemiluminescence (ECL) probes for efficient detecting Ru(bpy)32+ in the solution based on the quenching of the PL emission of CDs and enhanced ECL of Ru(bpy)32+, respectively. The PL and ECL probes exhibited a detection limit of 0.72 and 0.43μM, respectively. The PL and ECL properties of CDs and Ru(bpy)32+ will provide a new route to study the novel materials and broaden the use of them in analyte detection.