Sulfur-doped Carbon Dots Research Articles

Fluorescent cellulose hydrogels based on corn stalk of double sulfhydryl functional group modification for Hg(II) removal and detection

Ions of mercury, one of the most hazardous heavy metals in nature, pose serious risks to the environment and human health. Blue sulfur-doped carbon dots (SCDs) from corn stalks were utilized as material. The SCDs were incorporated into a carboxylated hydrogel modified with sulfur, and a compound gel (SCDs–KTOCS gel) was successfully fabricated for simultaneous fluorescence detection and Hg(II) adsorption. This enabled the effective identification and removal of Hg(II) from contaminated water. The chemical content, fluorescence properties, and adsorption behaviors of the SCDs–KTOCS–gels were analyzed. The results demonstrate that the SCDs–KTOCS–gels exhibited effective Hg(II) adsorption (193 mg/g) and an extensive linear spectrum for Hg(II) fluorescence emission (150–500 mg/L; detection limit = 1.5668 mg/L). The adsorption values fit well with the Temkin models and pseudo-second-order kinetics. Additionally, Hg(II) detection and adsorption in the SCDs–KTOCS–gels were examined. By exchanging the existing probe for a suitable one that fits various relevant applications, this study suggests an environmentally friendly and sustainable method of producing materials for removing and detecting Hg(II) and constructing a fluorescence hydrogel for the detection and adsorption of different metals.

One-step hydrothermal synthesis of F,N,S-doped photoluminescent carbon dots with yellowish-orange emission for sensitive Cu2+ ion detection: Environmental and biomedical applications

Herein, fluorine-, nitrogen-, and sulfur-doped carbon dots (FNS-CDs) were prepared via a one-step hydrothermal synthesis using flufenamic acid and thiourea as precursors, which showed yellowish-orange fluorescence both in aqueous solution and in the solid state. The as-prepared FNS-CDs were monodisperse and had an average diameter of 4 nm, good water solubility, a fluorescence quantum yield of 18.63 %, and excellent pH and ionic strength stability. The optimal excitation/emission wavelengths of the FNS-CDs were 406/570 nm, with an excitation-dependent wavelength range of 365–435 nm. The surface states, morphologies, and elemental compositions of the FNS-CDs were characterized using FTIR, XRD, TEM, and XPS. In addition, the FNS-CDs without any further modification exhibited high selectivity and sensitivity as nanosensors for Cu2+ over other metal ions. The PL quenching phenomenon can be used to detect Cu2+ ions within a linear range of 1–25 μM with a detection limit of 83.10 nM and an association constant of 1.29 × 104 M−1. The PL of the FNS-CDs was significantly quenched by Cu2+ ions through static quenching and was restored upon the subsequent addition of EDTA. The practical application was demonstrated through the detection of Cu2+ ions in real water samples, yielding recovery rates ranging from 97.8 % to 103.9 % with an RSD below 2.5 %. The FNS-CDs/Cu2+ complex exhibits potent antibacterial activity against S. aureus (85.27 %±2.1 %) and E. coli (91.31 %±1.6 %), whereas the FNS-CDs/Cu2+ has a higher inhibitory effect on the growth of E. coli. Furthermore, the FNS-CDs (100 μg/mL) were used for cell imaging, showing low toxicity to HCT-116 cells exhibited yellowish-orange fluorescence under a confocal microscope.

Synthesis of blue-sparkling N, S-doped carbon dots for effective detection of nitro explosive and Fe3+ ion and anti-counterfeiting studies

Highly blue-luminescent nitrogen & sulfur-doped carbon dots (N, S-CDs) made with homocysteine and ethylene diamine by simple single-step microwave-assisted style. The prepared carbon dots showed a higher photoluminescent quantum yield (PL-QY), which is found to be 45 %. FTIR and XPS analysis reveals that these N, S-CDs contain rich nitrogen, and sulfur as well as C=O and C=C functional groups. N, S-CDs had a mean size around 3-4 nm, very interestingly, obtained carbon dots exhibit excitation-dependent photoluminescent character, are water-soluble, and restore luminescent stability under UV-light exposure and a wide range of pH. The crafted N, S-CDs are hired for precise and discriminating detection of multiple water impurities such as Fe3+ ion and Picric acid. The complexation between oxygen species of N, S doped CDs, and Fe3+ ion follows the inner-filteration effect (IFE) and with Picric acid follows Forster Resonance Energy Transfer (FRET) for the doped N, S-CDs are found to be the utmost possible mechanism for the observed sensing performance. The lower detection limit (LOD) of Fe3+ sensors is about 0.11 µM and for picric acid is 0.07 µM. Moreover, these blue-emissive N, S-CDs as competent fluorescence sensors, have been used as fluorescent inks, as well as in advanced portable devices information security and filter paper-based probes for visual recognition might also hold prominent ability to make wider applications in biological systems.

Sulfur-doped carbon dots and g-C3N4 composite with thermally activated delayed fluorescence for white-light illumination and anticounterfeiting

Long-lived afterglow materials have attracted considerable interest in the fields of information security and illumination. Herein, a novel carbon dot (CD)-based thermally activated delayed fluorescence (TADF) material was synthesized by embedding sulfur-doped CDs (SCDs) into a graphitic carbon nitride matrix. The formation of covalent bonds between the matrix and SCDs enhances the stabilization of the triplet state in the composite, effectively suppressing nonradiative transitions. This stabilization, coupled with the effects of sulfur doping and covalent bonding, reduces the singlet–triplet splitting energy in the composite, thereby facilitating reverse intersystem crossing and resulting in TADF emission. This composite material has been successfully employed in the development of three types of CD-based white light–emitting diodes (WLEDs) excited by blue light. These WLEDs exhibit color temperatures of 7641, 5590, and 3215 K, with CIE coordinates of (0.30, 0.29), (0.33, 0.30), and (0.42, 0.40), respectively. The corresponding values of the color rendering index are recorded as 81.86, 90.13, and 75.07. In addition, this research provides a brief demonstration of the potential of the composite in information encryption and visible-light encryption applications. Furthermore, this study contributes to the advancement of CD utilization in the WLED field, promoting the development of next-generation CD-based WLEDs with exceptional properties.

Preparation and Application of a Sulfur-Doped Fluorescent Carbon Dots with Aggregation-Induced Emission Character.

As a new type of zero-dimensional nanomaterial, carbon dots are widely applied in various fields. However, most of the carbon dots have aggregation fluorescence quenching properties, which limited their practical applications. In this study, a novel sulfur-doped carbon dots (S-CDs) was prepared by solvothermal method. The properties of the S-CDs in ethanol solution and in solid state were investigated respectively. The results showed that the S-CDs have an excited wavelength dependent emission of blue fluorescence in ethanol solution, and have orange fluorescence emission in solid state and composite films, indicating the prepared S-CDs has aggregation-induced emission (AIE) performance. The main reason was that the presence of S-S bonds and the intramolecular rotation of aromatic rings were limited in solid state, resulting in its emission of orange fluorescence. Furthermore, the S-CDs could be applied to identify fingerprints, anti-counterfeiting.

Electrochemical oxidation of seawater using vanadium facilitated quaternary layered double hydroxides integrated with sulfur-doped carbon dots

This research introduces a novel approach to electrocatalysis for sustainable energy generation, revealing the MnCoCrV LDH@SCDs composite supported by nickel foam (NF) as a high-performance catalyst specifically designed for seawater electrolysis. Constructed by incorporating sulfur-doped carbon dots (SCDs) into MnCoCrV layered double hydroxide (LDH) and depositing them onto a nickel foam substrate, this electrocatalyst demonstrates exceptional efficiency in the oxygen evolution reaction (OER) under alkaline seawater conditions. MnCoCrV LDH@SCDs/NF attains a noteworthy current density of 10 mA/cm² with a minimal overpotential of 209.4 mV. Additionally, it demonstrates a reduced Tafel value of 81.5 mV/dec, indicating faster kinetics. The electrode maintains impressive long-term stability, sustaining efficiency for approximately 50 h at a constant current density of 10 mA/cm². The increased surface area and reduced charge transfer resistance contribute to substantial electrocatalytic performance in seawater. This performance is primarily attributed to improved conductivity, resulting from synergistic contributions from high-valence-state vanadium ions and electrochemically active functional groups in SCDs. The MnCoCrV LDH@SCDs/NF electrocatalyst stands out for its intricate features that not only promote efficient electron transfer but also effectively counteract interference from chloride anions in seawater electrolysis. This study underscores the innovative nature of MnCoCrV LDH@SCDs/NF as a pivotal development in electrocatalyst research, offering a promising avenue for harnessing renewable energy from seawater.

Synergistic Enhancement of Targeted Wound Healing by Near-Infrared Photodynamic Therapy and Silver Metal-Organic Frameworks Combined with S- or N-Doped Carbon Dots.

The literature data emphasize that nanoparticles might improve the beneficial effects of near-infrared light (NIR) on wound healing. This study investigates the mechanisms of the synergistic wound healing potential of NIR light and silver metal-organic frameworks combined with nitrogen- and sulfur-doped carbon dots (AgMOFsN-CDs and AgMOFsS-CDs, respectively), which was conducted by testing the fibroblasts viability, scratch assays, biochemical analysis, and synchrotron-based Fourier transform infrared (SR-FTIR) cell spectroscopy and imaging. Our findings reveal that the combined treatment of AgMOFsN-CDs and NIR light significantly increases cell viability to nearly 150% and promotes cell proliferation, with reduced interleukin-1 levels, suggesting an anti-inflammatory response. SR-FTIR spectroscopy shows this combined treatment results in unique protein alterations, including increased α-helix structures and reduced cross-β. Additionally, protein synthesis was enhanced upon the combined treatment. The likely mechanism behind the observed changes is the charge-specific interaction of N-CDs from the AgMOFsN-CDs with proteins, enhanced by NIR light due to the nanocomposite's optical characteristics. Remarkably, the complete wound closure in the in vitro scratch assay was achieved exclusively with the combined NIR and AgMOFsN-CDs treatment, demonstrating the promising application of combined AgMOFsN-CDs with NIR light photodynamic therapy in regenerative nanomedicine and tissue engineering.

Carbon Dots Derived from Jaggery Via Direct Heating: A Sensitive Platform for Ferric Ion Fluorescent Sensing

AbstractPhotoluminescent carbon dots (CDs) have greatest potential in fluorescence sensing, energy, bioimaging and environmental pollutant sensing. Heteroatom doping have dramatically enhanced fluorescent properties and stability of CDs. In this work, sulfur doped carbon dots (DCDs) using jaggery as carbon precursor through direct heating method at 180 °C. The synthesized DCDs were characterized through XRD, FTIR, XPS, TEM, Fluorescence and UV‐Visible spectroscopic techniques. The DCDs have 9 nm particle size with amorphous nature and surface decorated with −OH, C−S, C=O functional groups on surface because of contribution of major element like C, O, and S elements. The DCDs showing bright blue emission having 360 nm excitation and 460 nm emission wavelength. Further, the DCDs were employed for metal ion sensing and it selectively detects Fe3+ metal ion with 1.92 μg/mL of detection and 5.84 μg/mL limit of quantification. The experiment follows static quenching mechanism which is confirmed by fluorescence life time experiment. This low‐cost, time effective fluorescent sensitive carbon dots have potential application in environmental pollution control, biomedical and forensic applications.

Facile synthesis of carbon dots with blue-emitting for fluorescence determination of alizarin yellow R and temperature

Herein, a nontoxic, quick and one-step hydrothermal strategy was used to develop nitrogen and sulfur doped carbon dots (N,S-CDs). Sulfapyridine was selected as a sulfur source, and m-phenylenediamine was applied as a nitrogen source. In addition, the as-developed N,S-CDs indicated excitation-dependent feature, strong blue-emitting fluorescence, excellent photostability and anti-ion effect. Furthermore, the as-established N,S-CDs displayed an excellent linear characteristic for the determination of alizarin yellow R. The detection limit was 0.25 μM. Moreover, the as-developed N-CDs were successfully applied to determine alizarin yellow R in real samples.

Facile synthesis of sulphur-doped carbon dots (S-CDs) using a hydrothermal method for the selective sensing of Cr6+ and Fe3+ ions: application to environmental water sample analysis.

In this work, we used a one-step hydrothermal method to synthesize blue-emission sulfur-doped carbon dots (S-CDs) using jaggery as a carbon precursor. The synthesized carbon quantum dots showed low toxicity, good water solubility, anti-interference properties, and stable fluorescence. When excited at 310 nm, the S-CDs produced bright emission with a quantum yield of 7.15% at 397 nm. The S-CDs exhibited selective and sensitive quenching responses with limits of detection (LODs) of 4.25 μg mL-1 and 3.15 μg mL-1 for variable concentrations of Cr6+ and Fe3+, respectively, accompanied by a consistent linear relationship between fluorescence intensity and these concentrations. Fluorescence lifetime measurements were used to investigate the fluorescence quenching mechanism, which supports the static type of quenching. Outstanding benefits of the developed S-CD based fluorescence probe include its low cost, excellent sensitivity and selectivity, and ease of use for the detection of Cr6+ and Fe3+ ions. The developed carbon dot based fluorescent probe was successfully used to detect Cr6+ and Fe3+ ions in real water samples with an excellent recovery ratio.

Evaluation of N and S Codoped Carbon Dots as an Environment Friendly and High-Efficiency Inhibitor for X65 Steel in an Acidic Medium.

The high content of nitrogen and sulfur-doped carbon dots (N, S-CDs) was designed to prevent the corrosion of X65 steel in an acidic medium. The corrosion-inhibiting abilities of related nanomaterials for X65 steel were acquired by electrochemical experiments, and the corroded products were investigated by FT-IR, XPS, and Raman analysis. The conclusions confirm that the N, S-CDs are a high-efficiency inhibitor. When the concentration is 200 mg/L, the inhibitive efficiency of X65 steel can reach up to 99.1% and it interacts with X65 steel through chemical and physical adsorption. Additionally, results from the spectroscopic studies show that the S-group is the main contributor to the chemical adsorption process.

Methylmercury-sensitized “turn on” SERS-active peroxidase-like activity of carbon dots/Au NPs nanozyme for selective detection of ochratoxin A in coffee

The improvement and regulation of catalytic performance of nanozyme have long been pursued with sustained efforts. Herein, gold nanoparticles (S-CDs/AuNPs) with weak peroxidase-like (POD) activity were synthesized by Au-S bond using a sulfur doped carbon dots (S-CDs) as reducing agent and stabilizer. However, methylmercury (MeHg+) could selectively and sensitively regulate the POD-like activity of S-CDs/AuNPs. The catalytic activity of S-CDs/AuNPs was significantly activated with the addition of MeHg+, resulting in a significant enhancement of electromagnetic fields to present an obvious SERS signal. More intriguingly, the introduction of ochratoxin A (OTA) could simultaneously turn off the UV–vis absorbance signals and the surface-enhanced Raman scattering (SERS) signal. Based on these findings, a selective colorimetric-SERS dual-mode OTA detection strategy was established with gold amalgamation (Au@HgNPs) as the probe, and the low limit of detection (LOD) of OTA was 0.29 µgL−1 (Colorimetric) and 0.16 µgL−1 (SERS), respectively, with good recoveries from 95.9 to 104.0% (Colorimetric) and from 96.7 to 108.9% (SERS), respectively. The work paves a new way to design nanozyme-based colorimetric and SERS protocol for traces OTA residues analysis in foodstuff analysis.

Nanostructured N/S doped carbon dots/mesoporous silica nanoparticles and PVA composite hydrogel fabrication for anti-microbial and anti-biofilm application

Regarding the convergence of the worldwide epidemic, the appearance of bacterial infection has occasioned in a melodramatic upsurge in bacterial pathogens with confrontation against one or numerous antibiotics. The implementation of engineered nanostructured particles as a delivery vehicle for antimicrobial agent is one promising approach that could theoretically battle the setbacks mentioned. Among all nanoparticles, silica nanoparticles have been found to provide functional features that are advantageous for combatting bacterial contagion. Apart from that, carbon dots, a zero-dimension nanomaterial, have recently exhibited their photo-responsive property to generate reactive oxygen species facilitating to enhance microorganism suppression and inactivation ability. In this study, potentials of core/shell mesoporous silica nanostructures (MSN) in conjugation with carbon dots (CDs) toward antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli have been investigated. Nitrogen and sulfur doped CDs (NS/CDs) conjugated with MSN which were cost effective nanoparticles exhibited much superior antimicrobial activity for 4 times as much as silver nanoparticles against all bacteria tested. Among all nanoparticles tested, 0.40 M NS/CDs@MSN showed the greatest minimal biofilm inhibitory at very low concentration (< 0.125 mg mL−1), followed by 0.20 M NS/CDs@MSN (0.5 mg mL−1), CD@MSN (25 mg mL−1), and MSN (50 mg mL−1), respectively. Immobilization of NS/CDs@MSN in polyvinyl alcohol (PVA) hydrogel was performed and its effect on antimicrobial activity, biofilm controlling efficiency, and cytotoxicity toward fibroblast (NIH/3 T3 and L-929) cells was additionally studied for further biomedical applications. The results demonstrated that 0.40 M NS/CDs-MSN@PVA hydrogel exhibited the highest inhibitory effect on S. aureus > P. aeruginosa > E. coli. In addition, MTT assay revealed some degree of toxicity of 0.40 M NS/CDs-MSN@PVA hydrogel against L-929 cells by a slight reduction of cell viability from 100% to 81.6% when incubated in the extract from 0.40 M NS/CDs-MSN@PVA hydrogel, while no toxicity of the same hydrogel extract was detected toward NIH/3 T3 cells.

Dual-emissive waste oil based S-doped carbon dots for acetone detection and Cr(VI) detection/reduction/removal

Dual-emissive water-dispersible sulfur-doped carbon dots (S-CDs) were prepared through simple heat treatment of canola oil as a carbon source. The S-CDs revealed excitation wavelength-dependent and independent emission band in UV (327 nm) and the visible region (633 nm), respectively. The fluorescent S-CDs ranged from 4 to 9 nm in size and exhibited selectivity and linear “turn-off” fluorescence in the presence of Cr(VI) and acetone, making them potential nanosensors for their detection. Concentration-dependent red-shift of the S-CDs emission spectrum was observed in the presence of acetone, via incremental quenching of the peaks at 327 nm and 633 nm, accompanied by an emergence of new peak at adjacent higher wavelength. Linearity was observed in the range of 0.01–0.08 vol%, with a limit of detection (LOD) of 0.01 vol%. The nanoprobe was tested in spiked tap and river water for Cr(VI) along with acetone detection assays in spiked human urine and phosphate buffer solution. XPS analysis revealed the reduction of Cr(VI) to Cr(III) in the presence of S-CDs, a less toxic form. In addition to the optical detection, fluorescent probes incorporated into poly vinyl alcohol (PVA) matrix could be used for the removal of Cr(VI) ions from the contaminated water. Hence, the proposed S-CDs have potential applications as highly sensitive, selective, cost-effective, and environmental friendly sensors of acetone and Cr(VI), as well as for developing tools for the reduction and removal of Cr(VI) from contaminated water.

“One stone, five birds”: Ultrabright and multifaceted carbon dots for precise cell imaging and glutathione detection

Developing a single system capable of realizing bacterial Gram-type identification, fungal cell imaging, endoplasmic reticulum (ER) imaging, glutathione (GSH) detection, and normal/cancer cell discrimination with excellent performance is a huge challenge. Herein, ultrabright green-emitting endoplasmic reticulum-targeting sulfur-doped carbon dots (SCDs) with a quantum yield of ∼ 78 % were synthesized via the hydrothermal treatment of rose bengal (RB) and dl-cysteine (Cys). The obtained SCDs possessed excellent fluorescence stability, unique excitation-independent emission property, and satisfactory biocompatibility. We demonstrated that the SCDs could be used for fast (15 min) identification of Gram-positive bacteria due to their S-containing groups (e.g., sulfate and sulfydryl groups) and high-quality fungal cell imaging. We also demonstrated that the SCDs could realize selective and long-term ER imaging in normal/cancer cells, and achieve the monitoring of the cell behaviors during ER stress caused by starvation or various ER stress inducers in live cells. Further, by mixing SCDs and Cu2+, we prepared Cu/SCD nanocomposites (Cu/SCDs), in which the fluorescence of SCDs was quenched by Cu2+ and could recover upon the addition of GSH, realizing GSH detection with a limit of detection of 0.681 μM. Subsequently, based on the much higher GSH level of cancer cells than that of normal cells, Cu/SCDs were successfully applied for distinguishing normal cells from cancer ones. Overall, this work fabricates ultrabright and multifaceted SCDs for precise and high-quality cell imaging and GSH detection, confirming the great potential of SCDs for versatile biomedical applications.

Carbon dot nanosensors for ultra-low level, rapid assay of mercury ions synthesized from an aquatic weed, Typha angustata Bory (Patera)

A wild plant, Typha angustata Bory (Patera) was used as a precursor for synthesizing nitrogen and sulfur doped carbon dots (N, S-CDs) using hydrothermal method. The objective was to use an aquatic weed to develop an extremely sensitive sensor for fluorescence assay of mercury ions and cysteine in aqueous medium. N, S-CDs exhibited an unprecedented quantum yield (QY) of 83 %, not reported previously. The fluorescence intensity of N, S-CDs substantially quenched in presence of Hg 2+ ions, without being influenced with presence of interfering ions. The fluorescence intensity was regained absolutely in presence of cysteine, even after 10 cycles demonstrating exceptional reusability. Owing to extraordinary QY, the sensor exhibited ultra-low limits of detection (LOD) of 3.1 nM and 80 pM for Hg 2+ and cysteine, respectively indicating extraordinary efficacy of the sensor, also confirmed using XPS studies. At neutral pH and 2 min' incubation time, the linear detection ranges for Hg 2+ ions and cysteine were 0.01–60 μM and 0.05–12.5 μM, respectively. Fluorescence life decay studies exhibited that fluorescence quenching was static. Satisfactory recoverability in the range 95–102 % for real water samples, indicated high reliability and accuracy for detection of Hg 2+ ions. The synthesized sensor presented a potential for facile, fast and reliable platform for detection of Hg 2+ ions and cysteine for environmental remediation. • Wild plant, Typha angustata Bory was used as a precursor for N and S doped carbon dots. • The sensor exhibited “on-off” and “off-on” fluorescence sensing of mercury ions and cysteine. • Exceptionally low LOD of 3.1 nM and 0.08 nM were obtained for Hg 2+ and cysteine. • Excellent reversibility of fluorescence signal with cysteine was obtained for 10 cycles.

Alkali-assisted facile and scalable preparation of fluorescent sulfur-doped carbon dots with excellent optical and biological properties from thioctic acid

The preparation of high-performance heteroatom-doped fluorescent carbon dots (CDs) from renewable biomass or biometabolites hold an extensive attention. Here, we report an excess sodium hydroxide (NaOH) assisted method for the preparation of sulfur-doped carbon dots (S-CDs) at lower temperatures by using thioctic acid (TA). Excessive NaOH can promote the thermal decomposition process of thioctic acid in the hydrothermal process, thereby realizing rapid reaction rate (critical time 1 h) and scalable synthesis at low temperature (120 °C). The amount of NaOH and the reaction time were identified as the main factors affecting the synthesis, and the reaction of NaOH with disulfide bonds contributed the most to the generation of fluorescent S-CDs. This in-situ sulfur doping process resulted in excellent fluorescence properties, high relative quantum yield of 11.5%, low biotoxicity, good biocompatibility and excellent solubility, etc. In addition, this as-prepared fluorescent S-CDs showed excellent concentration dependence on ferric ions (Fe3+) and can achieve high-precision and selective detection. This work may provide a high-efficiency synthesis strategy for S-CDs for biological and detection applications.

Red-Emissive Sulfur-Doped Carbon Dots for Selective and Sensitive Detection of Mercury (II) Ion and Glutathione.

Carbon dots (CDs) show great potential in bioimaging and biosensing because of their good biocompatibility and excellent optical properties. However, CDs with intense red emissions for sensitive and selective detection are rarely reported. Herein, we prepared the red-emissive carbon dots (RCDs) through a facile hydrothermal method using tetra (4-carboxyphenyl) porphyrin (TCPP) and thiourea as starting materials. The obtained RCDs were characterized by TEM, XRD, and XPS. RCDs exhibited high water solubility and strong red emission (λem = 650 nm), with the fluorescence quantum yield as high as 26.7%, which was greatly higher than that of TCPP. Moreover, the as-prepared RCDs could be acted as a highly selective and sensitive probe for the detection of Hg2+ and glutathione (GSH) through the fluorometric titration method. The detection limits of Hg2+ and GSH were calculated to be 1.73 and 1.6 nM, respectively. The cellular experiments demonstrated the good biocompatibility of RCDs and their feasibility in bioimaging. Thus, this work provided a simple strategy to design and synthesize the highly red-emissive carbon dots, which showed promising application in biological and environmental assays.

Vortex-assisted dispersive solid-phase microextraction of ondansetron and domperidone using carbonized cockle shell modified with nitrogen and sulfur-doped carbon dots as a bio-based sorbent.

Herein, for the first time, the wasted cockle shells were modified with nitrogen and sulfur-doped carbon dots after carbonization and used as a suitable bio-based sorbent for the extraction of two important antiemetic drugs named ondansetron and domperidone. The extraction and separation were performed based on vortex-assisted dispersive solid-phase microextraction and high-performance liquid chromatography, respectively. Various techniques such as Fourier-transform infrared, fluorescence, field emission scanning electron microscopy, thermogravimetric analysis, nitrogen adsorption-desorption analysis, X-ray powder diffraction, and energy-dispersive spectroscopy were used to characterize the chemical composition of prepared sorbent. After examining the factors affecting the extraction efficiency and access to the optimal points using the response surface methodology, the linearity was in the range of 5-350μg/L with acceptable coefficients of determination (R2 >0.993). The limits of detection and quantification were in the range of 1.5-2.3 and 4.9-7.1μg/L, respectively. In the end, the proposed method was applied for the quantitative determination of trace levels of target analytes from pharmaceutical tablets, serum, and urine samples. The recoveries were more than 95.2%, indicating the proposed method's excellent accuracy.

Selective Detection of Fe3+ by Nitrogen–Sulfur-Doped Carbon Dots Using Thiourea and Citric Acid

The quantum yield and fluorescence properties of carbon dots are key issues for environmental detection. In this study, nitrogen–sulfur-doped carbon dots (N,S-CDs) were prepared hydrothermally by adding thiourea to provide the N source. By adjusting the ratio of citric acid (CA) to thiourea (N,S) and adding anhydrous ethanol, blue fluorescent doped carbon dots with a quantum yield of up to 53.80% were obtained. The particle morphology and crystalline organization of the N,S-CDs were analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Fourier transform infrared (FTIR) spectroscopy was used to illuminate distinct functional units through the recording of typical vibration bands. The luminescence properties of the N,S-CDs were investigated using ultraviolet–visible (UV-vis) absorption spectroscopy and steady-state fluorescence spectroscopy (PL). In addition, the fluorescence stability of the N,S-CDs was studied in detail. The results showed that the functional groups of the N,S-CDs chelate Fe3+ ions to quench the fluorescence of carbon dots. This shows that the N,S-CDs exhibit high selectivity for Fe3+ ions. With the addition of Fe3+ in the concentration of 0–100 µM, the fluorescence intensity of the N,S-CDs exhibited distinct and linear dependence upon the Fe3+ concentration (R2 = 0.9965), and the detection limit (D = 3ơ/m) was measured as 0.2 µM. The excellent optical properties and Fe3+ selectivity of the N,S-CDs provide a huge boost for application in the field of environmental monitoring.