Co-doped Carbon Nanodots Research Articles

A facile synthetic strategy to simultaneously achieve ultra-wide PL redshift of carbon nanodots and their high selectivity and sensitivity for Mn2+ detection

This paper presents a straightforward synthesis strategy for N, S co-doped carbon nanodots (N, S-CDs), aiming to achieve CDs emitting ultra-wide redshifts while obtaining excellent metal ion detection performance. The N, S-CDs display excellent fluorescence (FL) emission independence regardless of the excitation wavelength or concentration. By introducing a single dopant thiourea, the FL emission of CDs was red-shifted from 445 to 575 nm (∼130 nm). The doped N and S elements are discovered to cause the introduction of defective energy levels and an elevation in oxidation on the surface of CDs, which could potentially be the crucial factor for the ultra-wide redshift of FL emission. Also, it is investigated that solvent engineering is essential for the redshift of the emission peak, which can also be an effective way to synthesize multicolor CDs. Furthermore, the N, S-CDs can be utilized for measuring the water content in methanol solvent based on their solvent effects. Additionally, N, S-CDs have the capability of detecting Mn2+ with high selectivity and sensitivity. The interaction of CDs with Mn2+ resulted in an obvious change in both the UV absorption spectrum and FL lifetime. To put it differently, the reaction mechanism between CDs and Mn2+ probably includes mixed processes of dynamic and static quenching. Zeta potential tests additionally indicate that the FL quenching is strongly correlated with the surface condition of CDs. The outcomes and discoveries offer a fresh and viable method for achieving the simultaneous production of long-wavelength glowing CDs and their analysis and detection of metal ions as fluorescent probes.

Multi-purpose nitrogen and phosphorous codoped carbon nanodots for fluorescence-based sensing and bioimaging

A single-step, straightforward hydrothermal method is put forward to synthesize multi-purpose nitrogen and phosphorous co-doped carbon nanodots (N,P-CNDs). Endowed with excellent water-solubility, chemical, and optical stability, the synthesized CΝDs showed high prospects for utilization in chemical and physicochemical probing and bioimaging. Specifically, the CNDs were successfully applied as a pH and benzophenone-1 probe with satisfactory precision and accuracy, as well as to assess the activity of urease. The fluorescence intensity of CNDs decreases linearly with the pH rising within the range of 3.0–12.0. Based on the benzophenone-induced fluorescence quenching of the CNDs, an acceptable linear regression for detecting benzophenone-1 was achieved over the concentration range of 1.7–76 μM. Furthermore, the synthesized CNDs demonstrated exceptional potential for cell imaging, especially by selectively labeling cell nuclei. Capitalizing on the bioimaging capabilities and pH-sensing properties of the CNDs, we developed an integrated system for intracellular pH monitoring, which can enable improved understanding of cellular processes. This versatile system opens up new opportunities for the application of CNDs in sensing various chemical and physicochemical parameters, thereby expanding the horizons of their utilization in diverse fields. The fact that the synthesized CNDs exhibit all the above capabilities enables the development of a multi-purpose probing system. The findings of this study contribute to the expanding body of knowledge of CNDs applications, whereas the CNDs can be used in diverse fields, such as environmental monitoring and analysis, as well as in biological and medical research. Environmental implicationTo date, there have been reports about the endocrine-disrupting properties of benzophenones and their bioaccumulation in human tissues, genotoxicity, etc. Despite the importance in their detection, the number of analytical methods developed for the analysis of benzophenones is limited. In this study, the development of a fluorescence probe for the sensitive and selective determination of benzophenone-1 is described. Moreover, the developed carbon dots could also serve as a pH probe. This property was utilized for monitoring cellular pH changes, which may alter due to environmental conditions.Benzophenones have raised concerns due to their reported endocrine-disrupting properties, bioaccumulation in human tissues, and genotoxicity. Addressing the gap of limited analytical methods, our study focuses on the development of a highly sensitive and selective fluorescence probe for the determination of benzophenone-1. By successfully synthesizing carbon dots with unique optical properties, we not only enable the detection of benzophenone-1 but also harness the pH-sensing capabilities of these carbon dots. This dual functionality allows the monitoring of cellular pH changes, which can be influenced by environmental conditions. Through our research, we provide a valuable tool for the detection of benzophenones and pH monitoring, thereby supporting efforts towards environmental monitoring and risk assessment.

Highly fluorescent N, B-doped carbon nanodots performing as optical turn-off probes discerning Fe(II)

The interactions between metal ions and fluorescent probes are fundamentals for discerning the metal ions. Co-doped carbon nanodots (CNDs) have demonstrated the capacity to optically detect a wide variety of targets, including metal ions. In this work, the quenching of highly fluorescent, nitrogen (N) and boron (B) co-doped CNDs by Fe(II) ions was discovered and employed to differentiate Fe2+ in water samples and live cells. The fluorescence of the N,B-CNDs was quenched in a concentration-dependent manner with a need of very short reaction time (30 s), and the CNDs show good selectivity towards Fe(II) ions relative to other metal ions including Fe(III). The limit of detection (LOD) was calculated as 1.8 nM and the linear response range was 7 nM to 1 μM. The recovery percentage was determined to be 97%, 101%, and 103% for spiked Fe(II) concentrations of 31, 125, and 1000 nM, respectively, in tap water. The N,B-CNDs were able to monitor the presence of Fe(II) in living cells using the optical imaging of Fe(II) ions, and the quenching in cells was completed within one hour. Regarding the quenching mechanism, the photoinduced electron transfer (PET) procedure is proposed with support of cyclic voltammetry study on the CNDs upon addition of Fe(II). Overall, the N,B-CNDs promise as optical probes for the detection of Fe2+ in water and living cells, and demonstrated a satisfactory level of sensitivity and selectivity.

A facile approach for sulphur and nitrogen co-doped carbon nanodots to improve photothermal eradication of drug-resistant bacteria

In this study, we produced S, N co-doped CNDs (SN@CNDs) by using dimethyl sulfoxide (DMSO) and formamide (FA) as single sources of S and N, respectively. We varied the S/N ratios by adjusting the volume ratios of DMSO and FA and investigated their effect on the red-shift of the CNDs' absorption peak. Our findings demonstrate that SN@CNDs synthesized using a volume ratio of 5:6 between DMSO and FA exhibit the most significant absorption peak redshift and enhanced near-infrared absorption performance. Based on comparative analysis of the particle size, surface charge, and fluorescence spectrum of the S@CNDs, N@CNDs, and SN@CNDs, we propose a possible mechanism to explain the change of optical properties of CNDs due to S, N doping. Co-doping creates a more uniform and smaller band gap, resulting in a shift of the Fermi level and a change in energy dissipation from radioactive to non-radiative decay. Importantly, the as-prepared SN@CNDs exhibited a photothermal conversion efficiency of 51.36% at 808 nm and demonstrated exceptional photokilling effects against drug-resistant bacteria in both in vitro and in vivo experiments. Our facile method for synthesizing S and N co-doped CNDs can be extended to the preparation of other S and N co-doped nanomaterials, potentially improving their performance.

Aggregation-Induced White Light Emission and Solvent-Induced Dual Mode Multi-Analyte Sensing by Highly Crystalline Single Component Derived N, S Co-Doped Carbon Nanodots

Recently, carbon nanodots (CNDs), the zero-dimensional carbon nanomaterials, have attracted immense research interest. Besides inherent traits like biocompatibility, eco-friendliness, electron mobility, and water-soluble nature, CNDs, as a green material with inherent luminescence, have grabbed a lot of attention and have opened up applications in more real-world contexts. In the present study, we project methionine-derived N, S co-doped CNDs as an efficient candidate for white-light-emitting diode (WLED) applications and dual-mode multianalyte sensing, based on their covetable fluorescence. Here, a scalable, dry white-light-emitting solid material is achieved from the aqueous dispersion of CNDs through freeze-drying process, without encountering the usual hurdles that are met with in solid-state CND systems, such as aggregation-caused quenching (ACQ) in luminescence, incomplete dryness, and low yield. The present system stands distinct, as warm white light is achieved by simply integrating the white light emitting single-component derived CND powder with near ultraviolet LED chips (370 nm) without ACQ resistors or additional phosphors. WLEDs with a low correlated color temperature of 3762 K and a moderately high color rendering index, which are suitable for interior lighting, are achieved. Along with the optoelectronic application, the system is potent enough to respond to the presence of two biologically significant species, folic acid and Fe3+ ions, through a dual-mode operation, viz, fluorescence turn-on and turn-off strategies, respectively. Excellent selectivity from a galaxy of 34 analytes is noted for the system, with attractive detection limits of 0.709 and 14.08 μM for folic acid and ferric ion, in the respective order. A detailed investigation of the mechanisms proves the inner filter effect (IFE) and Forster resonance energy transfer-mediated fluorescence enhancement and IFE-mediated quenching effect, operating here.

Carbon nanodots calibrated fluorescent probe of QD@amphiphilic polyurethane for ratiometric detection of Hg (II)

Because of its strong toxicity to the ecosystem and human beings, mercury is regarded as one of the most hazardous heavy metals. Among various fluorescent sensors that have been designed for Hg (II) detection, the probes showing Hg (II) concentration dependent ratiometric fluorescent responses normally exhibited improved analytical performance. Herein, we have synthesized series of amphiphilic polyurethane (PU) to encapsulate hydrophobic fluorescent quantum dots (QD) via the emulsion confinement self-assembly, leading to generation of QD@PU colloids whose red emission can be selectively quenched by Hg (II) among other metal ions. In order to further improve the Hg (II) detection performance of QD@PU probe, the green emitting carbon nanodots (CD) were synthesized and conjugated with QD@PU, resulting to formation of CD-QD@PU colloidal probe showing ratiometric fluorescent response towards Hg (II), which finally contributed to an enhanced sensitivity and wider linear range for Hg (II) detection. More interestingly, both QD@PU and CD-QD@PU doped stretchable PU membranes still hold naked eye discrimination for Hg (II). Basically, the current work revealed a universal protocol to prepare fluorescent probe for Hg (II) detection using PU and low dimensional fluorescent nanoparticles as building blocks, which will open new way for design and fabrication of other advanced sensors and analytical devices. • An amphiphilic block copolymer of polyurethane (PU) were synthesized. • PU was used to encapsulate fluorescent quantum dots (QD) to obtain QD@PU colloids. • The fluorescence of QD@PU colloids can be selectively quenched by Hg (II). • Nitrogen and sulfur co-doped carbon nanodots (CD) was synthesized. • The CD-QD@PU probe allows specific detection of Hg (II) down to 10.5 nM.

Reversible detection of Hg(II) in pure water based on thymine modified nitrogen, sulfur co-doped carbon dots combined with antidote

Conventional Hg2+ visual sensors are unsustainable, hindering their practical application for improved water quality and health. In order to address this challenge, herein, N, S co-doped carbon nanodots (NS-CDs) were prepared and well characterized, presented the fluorescent monitoring for Hg2+ over other metal ions with the limit of detection (LOD) of 0.47 µM. Next, the CDs were successfully modified by thymine without any fluorescence labelling (referred to as T-NS-CDs). The sensitivity to Hg2+ cloud be noticeable enhanced due to the formation of T-Hg2+-T specific base pairs. Accordingly, the LOD was calculated with values as low as 1.56 nM. Furthermore, Hg2+ could be released and complexed with antidote (meso-2,3-dimercaptosuccinic acid) (DMSA-Hg2+), being the responsible for the reversible interconversion between T-Hg2+-T and DMSA-Hg2+. Interestingly, the proposed sensing system also applies to the fluorescent sensing for Hg2+ in tap water with satisfactory recoveries (96.97 %–101.38 %, RSD < 2 %). Thus, by simply combination of elemental doping and surface functionalization, the surface state and functionalities of CDs could be tailorable, endowing the fluorometric sensing towards Hg2+ in environmental system.

Efficient green synthesis of N,B co-doped bright fluorescent carbon nanodots and their electrocatalytic and bio-imaging applications

In this work, the nitrogen and boron co-doped carbon nanodots (NB-CNDs) were synthesized from the Solanum betaceum (S. betaceum) fruit extract viz. a simple hydrothermal carbonization method. The as-prepared NB-CNDs were characterized by regular spectroanalytical techniques. The nitrogen and boron co-doping on the surface of carbon nanodots were confirmed by FT-IR, EDAX and XPS studies. The optical properties of the NB-CNDs were studied using UV–Vis and Fluorescence spectroscopy. The quantum yield (QY) for the synthesized NB-CNDs was found to be 35%. The HR-TEM results revealed that the NB-CNDs were spherical in shape and the average size was 5 nm. The XRD, Raman and SAED studies were confirmed the amorphous nature of the NB-CNDs. The electrocatalytic activity of NB-CNDs on oxidation of hydrazine hydrate (HH) was studied by cyclic voltammetric techniques. The NB-CNDs were efficiently utilized as an electrocatalyst for the hydrazine hydrate oxidation in the potential range between −0.4 V to 1 V with the scan rate of 50 mV/s. Further, the synthesized fluorescent NB-CNDs were used as an effective fluorescent staining agent for the in-vitro bio-imaging studies.

Citric acid-based carbon dots: From revealing new insights into their biological properties to demonstrating their enhanced wound healing potential by in vitro and in vivo experiments

Citric acid, as a carbon precursor, has extensively been considered by researchers to synthesize fluorescent carbon nanodots (CNDs), which emit strongly in the blue spectral range. In an endeavor to repurpose CNDs for applications other than those until now reported, non-doped, nitrogen-doped, and nitrogen/sulfur co-doped CNDs, were synthesized using citric acid as one of the most exploited carbon sources. This study explored the effect of heteroatom doping on the biological properties of CNDs placing more emphasis on wound healing. The three CND species were examined with respect to cell proliferation/toxicity, cell migration, bactericidal, anti-inflammatory, and antioxidant properties. From the results, it became apparent that the N,S-doped CNDs exhibit remarkable bactericidal properties, while the N-doped CNDs exhibit the best anti-inflammatory and antioxidant properties. Based on it, in-vitro antioxidant experiments were carried out for the N-doped CNDs, which validated our findings. Next, the N-doped CNDs were evaluated for their wound healing potency by carrying out relevant in-vivo experiments. The results showed that wounds treated with the CNDs were healed four days faster than control wounds. This study provides valuable insights into inspiring new advancements of CNDs and draws a roadmap towards their broader range of biomedical applications underlining the potency in wound healing.

Rapid detection of silver ions based on luminescent carbon nanodots for multicolor patterning, smartphone sensors, and bioimaging applications.

Photoluminescent nitrogen and sulfur co-doped carbon nanodots (N,S-CNDs) were prepared via single-step hydrothermal carbonization using 2,4-diaminobenzenesulfonic acid (2,4-DABSA) as the sole precursor. The synthesized N,S-CNDs are easily dispersed in aqueous solution and have an average particle size of 5.0 ± 0.2 nm, showing a high quantum yield of 23.1% with excellent stability. The surface states of the N,S-CNDs were confirmed by Fourier-transform infrared spectroscopy, powder X-ray diffractometry, Raman spectroscopy, and X-ray photoelectron spectroscopy techniques. These N,S-CNDs were applied for the rapid visual sensing detection of Ag+ ions, which can be identified by their photoluminescent color change under ultraviolet (UV) light illumination at 365 nm within 5 s. Furthermore, a linear correlation coefficient between P0/P and Ag+ ions was observed in the linear range of 0-1.2 μM with a detection limit of 7.88 nM. The proposed method was successfully used for the sensitive detection of Ag+ ions in real samples with satisfactory recoveries and relative standard deviation. The photoluminescence properties of N,S-CND and N,S-CNDs/Ag+ aqueous solutions were demonstrated by their invisible inks that can only be seen when irradiated with UV light. The RGB values of N,S-CND and N,S-CNDs/Ag+ aqueous solutions were measured using a color selector smartphone application. In addition, N,S-CND and N,S-CNDs/Ag+ aqueous solutions were further used for the multicolor imaging of HCT-116 cancer cells due to the low toxicity of N,S-CNDs.

Nitrogen, sulfur, phosphorus, and chlorine co-doped carbon nanodots as an "off-on" fluorescent probe for sequential detection of curcumin and europium ion and luxuriant applications.

Nitrogen, sulfur, phosphorus, and chlorine co-doped carbon nanodots (NSPCl-CNDs) were fabricated by acid-base neutralization and exothermic carbonization of glucose. The obtained NSPCl-CNDs possess excellent fluorescence properties and good biocompatibility. Curcumin (Cur) can dramatically quench the fluorescence of NSPCl-CNDs based on a synergistic effect of electrostatic interaction, inner filter effect, and static quenching, so a "turn-off" fluorescent probe for Cur detection was constructed with linear ranges of 0.24-13.16μM and 13.62-57.79μM. The LOD and LOQ of this fluorescent probe for Cur are 8.71nM and 29.03nM, respectively. More importantly, the fluorescence of the NSPCl-CNDs-Cur system can be recovered by europium ion (Eu3+), so a "turn-on" fluorescent probe for Eu3+ determination was established. The linear range, LOD, and LOQ for the detection of Eu3+ were 2.36-32.91 μΜ, 73.29nM, and 244.30nM, respectively. The proposed fluorescence methods were successfully utilized for Cur and Eu3+ determination in real samples with recoveries in the range 95.64-104.13% and 97.06-98.70%, respectively. Furthermore, the qualitative analysis of Cur can be realized by reagent strips with satisfying results. Finally, the as-constructed "off-on" fluorescent probe was successfully used to sequentially analyze Cur and Eu3+ at the cellular level. This method is simple and easy to implement, manifesting that NSPCl-CNDs have potential application value in fluorescent probing, food and drug testing, environmental monitoring, and cellular labeling. Graphical abstract.

Highly sensitive fluorescent probe for selective detection of hypochlorite ions using nitrogen–fluorine co-doped carbon nanodots

Hypochlorite ions (ClO−) are widely used in bleaching agents and disinfectants. However, high concentrations of chloride species are harmful to human health. Therefore, effective methods for the detection of ClO− ions are required. In this study, using 4-fluorophthalic acid and glycine, nitrogen–fluorine co-doped carbon nanodots (N,F-CDs) were synthesized by one-pot hydrothermal synthesis for use as a fluorescent probe for the fluorometric detection of ClO− in aqueous media, based on the inhibition of n → π* transitions. The excitation and emission peak centers of the N,F-CDs are at 387 and 545 nm, respectively. The N,F-CDs show a fast quenching response (<1 min) for ClO− and can be used in a wide pH range (pH 4–13). Under optimal conditions, the fluorescence intensity decreased with increase in the ClO− concentration from 0 to 35 μM, and a low limit of detection (9.6 nM) was achieved. This probe possesses excellent selectivity and high sensitivity and was used to analyze standardized samples of piped water, achieving a satisfactory recovery. Thus, this nitrogen–fluorine co-doped nanodot probe is promising for the detection of pollutants.

Inner filter effect as a sensitive sensing platform for detection of nitrofurantoin using luminescent drug-based carbon nanodots.

In the present paper, a sensitive and selective inner filter effect sensing platform was designed to detect nitrofurantoin (NIT) in pharmaceutical dosage form. Nitrogen and phosphorus co-doped carbon nanodots (CNDs) prepared via solvothermal treatment of folic acid and phosphoric acid. The prepared CNDs exhibit greenish fluorescence at 470nm when excited at 340nm with fluorescence quantum yield up to 40%. The CNDs exhibit high stability in various pH, temperature, and ionic strength which adds valuable merits to its pharmaceutical applications. The emission is quenched in the presence of absorber (here NIT) while the fluorophores were not quench by the presence of common pharmaceutical excipients. A fluorometric assay was fabricated to determine NIT in capsules by quenching of the CNDs. The linear response for the proposed method was from 5.0μM to 90μM with the detection limit being 1.4μM. To validate the method, the recovery of NIT in spiked sample was measured which was 96.6% -103.3%. The method was applied to the determination of NIT in pharmaceutical capsule samples, with comparable results of a reference method stated by the British Pharmacopeia (BP). Furthermore, the sub-acute toxicity studies of CNDs were investigated using normal male Balb/c mice forcefully drunk with 3 different dosages of CNDs. Animals did not produce treatment related signs of toxicity or mortality in any of the animals tested during the 28days observation period. Additionally, no significant (P>0.05) changes in the body weight, haematological and biochemical parameters compared with the control group were not revealed. Similarly, histopathological examination of the internal vital organs did not show any morphological alterations.

Highly Luminescent and Biocompatible P and N Co-Doped Passivated Carbon Nanodots for the Sensitive and Selective Determination of Rifampicin Using the Inner Filter Effect.

The determination of rifampicin in pharmaceutical dosage forms using a rapid, sensitive, selective, biocompatible, and low-cost method is of vital importance in the pharmaceutical analysis field to ensure its concentration is within the effective range when administered. In this study, nitrogen-and-phosphorous-doped carbon nanodots (CNDs) were prepared using a single-step hydrothermal method with ciprofloxacin as the starting material. The CNDs showed a highly intense blue fluorescence emission centered at 450 nm, with a photoluminescence quantum yield of about 51%. Since the absorption of rifampicin was the same as the excitation spectrum of CNDs, inner filter effect (IFE) quenching occurred and it was used as a successful detection platform for the analysis of rifampicin in capsules. The detection platform showed a dynamic linear range from 1 to 100 μM (R2 = 0.9940) and the limit of detection was 0.06 μM (when S/N = 3). The average spike recovery percentage for rifampicin in the capsule samples was 100.53% (n = 5). Moreover, the sub-chronic cytotoxicity of CNDs was evaluated on healthy male mice (Balb/c) drenched with different amounts of CNDs (10 and 50 mg/kg). During this study period, no mortalities or toxicity signs were recorded in any of the experimental subjects. Based on the cytotoxicity experiment, the proposed nano-probe is considered safe and biocompatible.

High photoluminescence nitrogen, phosphorus co-doped carbon nanodots for assessment of microbial viability

Assessment of microbial viability plays a key role in human health protection. Optical imaging based on fluorescent dyes is a simple and convenient way to assess microbial viability. However, it is still a challenge to obtain stable, nontoxic and low-cost dyes. Herein, we prepared a nitrogen and phosphorus co-doped carbon nanodots (N, P-CDs) via a one-step solvothermal method. The prepared CDs possess plenty of functional groups and exhibit high stability, good biocompatibility, excellent photoluminescent and low toxicity. Especially, the properties of high quantum yield (89.9%) and highly negative surface charge (−41.9 mV) make the prepared N, P-CDs ideal materials for microbial differentiation. Compared with commercial dyes, our CDs are more stable, cost less, which can rapidly distinguish dead microorganisms from living ones with higher specificity.

Dual functional highly luminescence B, N Co-doped carbon nanodots as nanothermometer and Fe3+/Fe2+ sensor

Dual functional fluorescence nanosensors have many potential applications in biology and medicine. Monitoring temperature with higher precision at localized small length scales or in a nanocavity is a necessity in various applications. As well as the detection of biologically interesting metal ions using low-cost and sensitive approach is of great importance in bioanalysis. In this paper, we describe the preparation of dual-function highly fluorescent B, N-co-doped carbon nanodots (CDs) that work as chemical and thermal sensors. The CDs emit blue fluorescence peaked at 450 nm and exhibit up to 70% photoluminescence quantum yield with showing excitation-independent fluorescence. We also show that water-soluble CDs display temperature-dependent fluorescence and can serve as highly sensitive and reliable nanothermometers with a thermo-sensitivity 1.8% °C−1, and wide range thermo-sensing between 0–90 °C with excellent recovery. Moreover, the fluorescence emission of CDs are selectively quenched after the addition of Fe2+ and Fe3+ ions while show no quenching with adding other common metal cations and anions. The fluorescence emission shows a good linear correlation with concentration of Fe2+ and Fe3+ (R2 = 0.9908 for Fe2+ and R2 = 0.9892 for Fe3+) with a detection limit of of 80.0 ± 0.5 nM for Fe2+ and 110.0 ± 0.5 nM for Fe3+. Considering the high quantum yield and selectivity, CDs are exploited to design a nanoprobe towards iron detection in a biological sample. The fluorimetric assay is used to detect Fe2+ in iron capsules and total iron in serum samples successfully.

Nitrogen and sulfur co-doped carbon nanodots in living EA.hy926 and A549 cells: oxidative stress effect and mitochondria targeting

Carbon nanodots (CNDs) have been studied in the field of biomedicine, such as drug delivery, bioimaging and theragnosis because of their superior biocompatibility and desirable optoelectronic properties. However, limited assessments on the biological effects of CNDs, particularly the effect on oxidative stress and toxicity in living cells, are not adequately addressed. In this work, a type of nitrogen, sulfur-doped carbon nanodots (N,S-CNDs), which were found to have strong antioxidant capacity in free radical scavenging in physicochemical conditions, was investigated through measuring the fluctuations of the intracellular reactive oxygen species (ROS), such as the hydrogen peroxide and superoxide anion, at different dose exposure in two types of cell lines, EA.hy926 and A549 cells. Instead of showing antioxidative capacity, the results indicate the uptake of the N,S-CNDs induces the production of intracellular ROS, thus causing oxidative stress and deleteriousness to both cell lines. The mitochondrial membrane potential of the cells was monitored upon the N,S-CNDs treatment and found to increase monotonically with the concentration of the CNDs. In addition, the confocal imaging of the cells confirms the localization of the CNDs at the mitochondria. More evidence suggests that the N,S-CNDs may stimulate ROS generation by interacting with the electron transport chain in the mitochondrial membrane due to the sulfur composite in the CNDs.

Fluorometric and colorimetric determination of hypochlorite using carbon nanodots doped with boron and nitrogen.

Carbon nanodots doped with boron and nitrogen (BN-CDs) with an average diameter of around 11nm were prepared by a hydrothermal approach using adenine and 3-aminobenzene boronic acid as the starting materials. The atomic ratio of boron to nitrogen atomic in the BN-CDs is approximately 1:1. This indicates that a large fraction of N atoms goes lost during preparation because the B/N ratio of the precursors is about 1:6. The BN-CDs display blue fluorescence (best measured at excitation/emission wavelengths of 305/380nm) which is independent of the excitation wavelength. On exposure to hypochlorite anion, fluorescence is quenched and the color of the solutions changes from yellow to brown. Fluorescence drops linearly in the 0.1-1000μM hypochlorite concentration range. The colorimetric response, best measured as the absorbance ratioat 236/260nm, ranges from 0.3 to 4.0mM. The color changes can be readily detected visually. The probe was applied to the determination of hypochlorite in living cells and in (spiked) tap water. Graphical abstract Excitationwavelength-independent fluorescent boron and nitrogen codoped carbon nanodots (BN-CDs) were obtainedbya hydrothermal approach. The BN-CDs were usedto detect hypochlorite in wastewaterby afluorometric and colorimetric dual-readout assay.

Using easily prepared carbon nanodots to improve hole transport capacity of perovskite solar cells

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is the most widely-used transparent anode material of commercialization. However, the partially bonding between PSS and PEDOT greatly decreases the structural and electronic homogeneity of PEDOT:PSS system. In view of their molecular structure and functional groups, a S, N co-doped carbon nanodots (CNDs) was developed as ameliorant to prepare PEDOT:PSS:CNDs hole transport layer. The uncombined S double bond introduces more microcosmic interstice inside CNDs, accompanying with many N-rich amino on the surface. This highly reactive products can band the redundant PSS and remove the insulating component from PEDOT:PSS mixture, leading to the conductivity and structural homogeneity improvement. The hole-transport capability of PEDOT:PSS:CNDs is systematically investigated in inverted planar hetero-junction (PHJ) perovskite solar cells (PSCs) fabricated in air, and an optimized power conversion efficiency (PCE) of 18.03% was achieved, which is superior to PEDOT:PSS based PSCs produced under atmospheric. This work offers a new strategy to improve the charge transfer capability of PEDOT:PSS in PSCs.

Ultrafast and Energy-saving Synthesis of Nitrogen and Chlorine Co-doped Carbon Nanodots via Neutralization Heat for Selective Detection of Cr(VI) in Aqueous Phase.

In this work, it is presented for the first time that nitrogen and chlorine co-doped carbon nanodots (N,Cl-CDs) were synthesized by simply mixing glucose, concentrated hydrochloric acid (HCl), and 1,2-ethylenediamine (EDA). No external heat was employed; the neutralization reaction served as the heat source. The glucose served as the carbon source while EDA and HCl were the N and Cl dopants, respectively. The fluorescence of N,Cl-CDs was adequately quenched by hexavalent chromium Cr(VI) based on a combination of dynamic quenching and inner filter effect (IFE). Accordingly, an efficient N,Cl-CDs-based fluorescence probe was established for sensitive and selective detection of Cr(VI). The proposed fluorescence sensor provides a linear recognition range for Cr(VI) determination from 3 to 40 µM with a limit of detection (LOD) of 0.28 µM (14.6 µg/L). The proposed fluorescence method was successfully utilized to detect Cr(VI) in different water samples with satisfactory results. The spike recoveries vary from 97.01% to 103.89% with relative standard deviations (RSDs) of less than 0.82%. This work highlights the development of a simple, ultrafast, and energy-saving one-step synthetic route to fabricate N,Cl-CDs for highly selective and sensitive detection of Cr(VI) in real water samples. It is anticipated that the proposed fluorescence method could be further explored and widely used for Cr(VI) detection in the environmental industry.