Phosphorus Co-doped Carbon Dots Research Articles

Investigation of the Application and Mechanism of Nitrogen and Phosphorus Co-doped Carbon Dots for Mercury Ion Detection.

In this paper, we obtained nitrogen and phosphorus co-doped carbon dots through a hydrothermal method using o-phenylenediamine and citric acid in a 40% phosphoric acid environment. The carbon dots emitted fluorescence at 476nm under excitation at 408nm and exhibited good selectivity and high sensitivity towards mercury ions. These carbon dots showed excellent dispersibility in water and maintained stable fluorescence even in high concentration salt environments. The interaction between mercury ions and functional groups on the carbon dots surface through electrostatic interaction resulted in static quenching. Simultaneously, by detecting the lifetime and transient absorption spectra of the carbon dots, we observed that the coordination of mercury ions with the carbon dots broadened the band structure of the carbon dots, and the existing photoinduced electron transfer process increased the non-radiative transition channel. The combined effect of dynamic quenching and static quenching significantly reduced the fluorescence intensity of the carbon dots at 476nm. The carbon dots exhibited linear detection of mercury ions in the range of 0.01-1 µM, with a detection limit as low as 0.0245 µM. In terms of practical water environmental detection applications, these carbon dots were able to effectively detect mercury ions in tap water and lake water, demonstrating their broad application prospects in the field of environmental metal analysis.

Effect of nitrogen and phosphorus co-doped carbon dots containing layer-by-layer self-assembled coating on UV resistance and thermal stability of cotton fabric

Effect of nitrogen and phosphorus co-doped carbon dots containing layer-by-layer self-assembled coating on UV resistance and thermal stability of cotton fabric

Tunable fluorescent biomass-derived carbon dots for efficient antibacterial action and bioimaging

Carbon dots (CDs)-based antibacterial biomaterials offer great potential in addressing the severe threat of antibiotic-resistant bacteria to public health. Positively charged CDs usually adhere on bacterial membranes via electrostatic interactions, however, they may cause hemolysis and cytotoxicity, and dissatisfactory fluorescence emission restricts their applications in bioimaging. Herein, we developed a negatively charged tunable multicolor nitrogen and phosphorus co-doped CDs (N, P-CDs) from mango peel, a renewable food waste biomass. The N, P-CDs exhibit good biocompatibility and photostability, thus could be adopted to multicolor cell labeling in vitro. More importantly, the negatively charged N, P-CDs possess intrinsic antibacterial activity against E. coli and S. aureus, and antimicrobial mechanisms were investigated by real-time quantitative PCR (RT-qPCR). We found the different mechanisms of N, P-CDs against E. coli and S. aureus, the antibacterial mechanism of N, P-CDs against E. coli mainly involve inhibition of binary fission proliferation and transcription of genetic information, interference with carbon metabolism and sugar conversion, thus inducing growth arrest and cell death. For S. aureus, N, P-CDs could serve as quorum sensing (QS) inhibitor to disrupt QS system, inhibit biofilm formation, DNA replication, cell division, and signal transmission. Our study provides important insights into antibacterial mechanism of CDs at the molecular level, which may facilitate the further exploration and application of natural resources-based antibacterial biomaterials.

A Smartphone-Integrated Molecularly Imprinted Fluorescence Sensor for Visual Detection of Chlortetracycline Based on N,P-Codoped Carbon Dots Decorated Iron-Based Metal-Organic Frameworks.

The residue of chlortetracycline is potentially hazardous to human health; it is meaningful to exploit a portable, rapid, sensitive, and selective method for detection of chlortetracycline (CTC). In this study, a novel fluorescence bionic sensing probe (NH2-MIL-53&N,P-CDs@MIP) was successfully prepared based on the nitrogen and phosphorus codoped carbon dots decorated iron-based metal-organic frameworks combining with molecular imprinted polymer for the detection of CTC. A fluorescence intensity-responsive "on-off" detection of CTC on account of the inner-filter effect (IFE) was achieved by NH2-MIL-53&N,P-CDs@MIP. Under the optimal conditions, the fluorescence quenching degree of NH2-MIL-53&N,P-CDs@MIP presented a good linear relationship with the CTC concentration in the range 0.06-30 μg mL-1 and the limit of detection (LOD) was 0.019 μg mL-1. The fluorescent probe was applied to detect CTC in milk samples, and experimental results showed a good recovery rate (88.73%-96.28%). Additionally, a smartphone-integrated fluorescence sensing device based on NH2-MIL-53&N,P-CDs@MIP was exploited to replace the expensive and bulky fluorescence spectrophotometer for quantitative determination of CTC with the LOD of 0.033 μg mL-1. The sensing system showed high selectivity, strong stability, high specificity, and portability, which provide a great strategy for the quantitative detection of antibiotic residue.

Nitrogen and Phosphorus Co-Doped Carbon Dots for the Growth Promotion of Water Spinach

Carbon dots have received much attention due to their unique physicochemical properties and diverse applications in bioimaging, optoelectronic devices, catalysis, and agriculture. Here, in this work, we report a simple hydrothermal synthesis of nitrogen and phosphorus−doped carbon dots (N, P−CDs). The optical and physical properties of the synthesized N, P−CDs are analyzed using systematical spectroscopy and electrical characterization. The synthesized N, P−CDs show strong photoluminescence at 626 nm and demonstrate high stability under UV light and other conditions. Moreover, we incorporate the synthesized N, P−CDs into water spinach by root spraying and leaf spraying. It is found that N, P−CDs could effectively promote the growth of water spinach by accelerating the photosynthetic rate, and increasing the content of total phenols, anthocyanins, and flavonoids in water spinach.

Hydrothermal Synthesis of Nitrogen and Phosphorus Codoped Carbon Dot Interfacial Modification Layer for Efficient Charge Transfer between ZnO Electron Transport Layer and PTB7:PC70BM Active Layer

The interface between the active layer and the charge-transporting layer is critical for performance improvement in polymer solar cells (PSCs). The use of zinc oxide (ZnO) as an electron transport layer (ETL) in PSCs was limited due to inherent defects in the surface of ZnO prepared by the sol-gel method, mismatched energy bands with the photoactive layer, and incompatibility between the photoactive layer and ZnO ETL. In this study, nitrogen and phosphorus codoped carbon dots (N & P-CDs) were prepared from Ensete ventricosum (false banana) and used as an interfacial modification layer for ZnO ETL. The inverted devices with structures ITO/ZnO/N & P-CD/PTB7:PC70BM/Al were fabricated to investigate the charge transfer dynamic between the active layer and ETL interface modification with N & P-CDs. We have observed that the interfacial modification between the ZnO ETL and the active layer, using N & P-CDs, improves the charge transfer between ZnO ETL and PTB7:PC70BM active layer. The obtained result shows that the ETL/BHJ interface resistance of the devices with ZnO:undoped CDs, ZnO:N-CDs, ZnO:P-CDs, and ZnO:N & P-CD ETLs decreases dramatically from 103.4 to 84.04, 78.16, 37.88, and 28.9 Ω, respectively. This is due to the improvement of charge extraction efficiency by smoothing ZnO surface defects and minimizing the band mismatch between the active layer and ZnO using N & P-CDs. The results indicate that the water-soluble N & P-CDs developed in this study have the potential to be used for efficient free charge carrier extraction for PSCs.

Dual functions of nitrogen and phosphorus co-doped carbon dots for drug-targeted delivery and two-photon cell imaging

Heteroatom-doping carbon dots (CDs) have excellent fluorescence properties. In the paper, nitrogen (N) and phosphorus (P) co-doped CDs (N, P-CDs) were prepared through the hydrothermal method and characterized by TEM, PXRD, FT-IR, 13C NMR, XPS, UV–vis, and fluorescence spectra. The optical properties and drug (doxorubicin) - delivery performance of N, P-CDs were also studied. The results showed that the average size of N, P-CDs was 3.64 nm and the quantum yield was 30 %. The N, P-CDs had down- and up-conversion fluorescence properties, and the luminescence mechanism of the N, P-CDs was explained. The drug loading capacity of N, P-CDs was 39.11 %, and the drug delivery system (N, P-CDs-DOX) had low cytotoxicity, sustained release, and pH-targeted properties. The in vitro release of N, P-CDs-DOX belonged to the Weibull model and Fick diffusion, exhibiting the same release model and mechanism with free DOX. The N, P-CDs could deliver DOX successfully, which was demonstrated by the co-collocation of N, P-CDs and DOX in SH-SY5Y cells through single/two-photon imaging. N, P-CDs could potentially be used in drug-targeted delivery and cell imaging.

Calcium and phosphorus co-doped carbon dots enhance osteogenic differentiation for calvarial defect repair in situ

Calvarial bone defect remains a clinical challenge due to the lack of efficient osteo-inductive agent. Herein, a novel calcium and phosphorus codoped carbon dot (Ca/P-CD) for bone regeneration was synthesized using phosphoethanolamine and calcium gluconate as precursors. The resultant Ca/P-CDs exhibited ultra-small size, stable excitation dependent emission spectra and favorable dispersibility in water. Moreover, Ca/P-CDs with good biocompatibility rapidly entered the cytoplasm through endocytosis and increased the expression of bone differentiation genes. After mixing with temperature-sensitive hydrogel, Ca/P-CDs were injected in situ into calvarial defect and promoted the repair of bone injury. These Ca/P-CDs provide a new treatment method for the bone repair and should be expended the application in the biomedical fields.

Fluorescence turn-off sensing of lead and gentamicin based on phosphorus and chlorine co-doped carbon dots

In the present study, CQDs co-doped with phosphorus and chlorine have been synthesized by a hydrothermal technique. The synthesized CQDs possess a mean size of <20 nm and show excitation-independent features. The investigations presented that the CQD’s fluorescence intensity was markedly quenched in the presence Pb2+ due to the formation of a stable non-luminescent complex that regarding this mechanism, a fluorescent platform was offered for Pb2+ ions in water samples. Furthermore, the gentamicin adding into the P, Cl-CQDs + Pb system had a more quenching effect on CQD’s fluorescence and so another probe was proposed for gentamicin determination. The detection limits for the proposed methods were 0.001 µg.mL−1 for Pb2+and 0.003 µg.mL−1 for gentamicin, respectively. The probe was successfully utilized in the environmental samples with high accuracy and selectivity.

Nitrogen and phosphorus co-doped carbon dots as an effective fluorescence probe for the detection of doxorubicin and cell imaging

Nitrogen and phosphorus co-doped carbon dots (NPCDs) with bright blue fluorescence were established by a hydrothermal method using alanine and diammonium phosphate as raw materials. The NPCDs were characterized by transmitted electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, ultraviolet–visible absorption (UV–vis), and fluorescence spectroscopy to investigate the morphology, elemental composition, and optical properties. The NPCDs had good water solubility, high dispersibility with an average diameter of only 2.77 nm, and satisfactory optical properties with a fluorescence quantum yield of 17.2%. The NPCDs were employed for the detection of doxorubicin (DOX). A good linear response of the NPCDs in the range 0.5–6.5 μM was obtained for DOX with a detection limit of 12 nM. The NPCDs were also applied to the analysis of real samples, urine and serum, with a recovery of 92.0–109.3%. The low cytotoxicity and good biocompatibility of the NPCDs were indicated by an MTT assay and cell imaging of HeLa cells. Compared with other detection systems, using NPCDs for DOX detection was a facile and efficient method with good selectivity and sensitivity.

Microwave-assisted facile synthesis of N, P co-doped fluorescent carbon dot probe for the determination of nifedipine.

A simple and fast microwave synthesis method was applied for the preparation of several carbon dots (CDs) from various combinations of urea, phosphoric acid, and B-alanine as nitrogen, phosphorus, and carbon precursors. The maximum quantum yield (44%) was obtained for nitrogen and phosphorus co-doped carbon dots (N, P-CDs) prepared from urea, B-alanine, and phosphoric acid. Furthermore, N, P-CDs were exploited to synthesize a simple and sensitive fluorometric probe to determine nifedipine (NFD). We determined that the analytical response of the designed sensor could be affected by the kind of dopant and synthesis precursors. It is worth mentioning that the fluorescence intensity of N, P-CDs was weakened by NFD, and no fluorescence quenching was observed for other prepared CDs. The NFD-developed sensor demonstrated a linear response range of 3.3 × 10-8-3.2 × 10-5mol/L, with the detection limit of 1.0 × 10-8mol/L. The sensor was successfully applied to measure NFD in human biological fluids.

Fluorescence Turn-Off Sensing of Lead and Gentamicin Based on Phosphorus and Chlorine Co-Doped Carbon Dots

Fluorescence Turn-Off Sensing of Lead and Gentamicin Based on Phosphorus and Chlorine Co-Doped Carbon Dots

Hydrothermal Synthesis of Nitrogen and Phosphorus Co-Doped Carbon Dots Interfacial Modification Layer for Efficient Charge Transfer between ZnO Electron Transport Layer and PTB7:PC &lt;sub&gt;70&lt;/sub&gt;BM Active Layer

Hydrothermal Synthesis of Nitrogen and Phosphorus Co-Doped Carbon Dots Interfacial Modification Layer for Efficient Charge Transfer between ZnO Electron Transport Layer and PTB7:PC &lt;sub&gt;70&lt;/sub&gt;BM Active Layer

Nitrogen and phosphorus co-doped carbon dots for developing highly flame retardant poly (vinyl alcohol) composite films

In this work, nitrogen and phosphorus co-doped fluorescent carbon dots (N,P-CDs) were synthesized from m-phenylenediamine and phosphoric acid in a one-step hydrothermal method. Then, novel flame retardant PVA composite films (PVA/N,P-CDs) were prepared by introducing N,P-CDs into the PVA matrix via solvent mixing. Subsequently, the flame retardancy, thermal stability, mechanical properties and transparency of the PVA/N,P-CDs films were investigated through vertical burning tests (UL-94), thermogravimetric analysis (TGA), mechanical property tests and UV–visible spectroscopy, respectively. In addition, the structure of the residual char of the composite films was studied by SEM, EDS, in situ FTIR and Raman spectroscopy, and the corresponding flame retardant mechanisms were analysed. It was demonstrated that the addition of a small amount of N,P-CDs endows films with remarkable anti-dripping performance. The limiting oxygen index (LOI) of the PVA/N,P-CDs composite films increased to more than 30% and achieved a UL94 VTM-0 rating when the N,P-CDs solution (the N,P-CDs are diluted 30 times) was higher than 20%. Moreover, the introduction of N,P-CDs solution increased the residual char from 12.4% for neat PVA to 36.4% for PVA/N,P-CDs. These improvements are attributed to the N,P-CDs in the N,P-CDs solution, which are contribute to the formation of a larger char barrier layers, and a less phosphoric acid in the N,P-CDs solution can effectively promote the dehydration, crosslinking and cyclization of PVA matrix to form a close and continuous char barrier layers. Importantly, N,P-CDs considerably improve the high temperature thermostability and mechanical properties of PVA films without affecting transparency and endow these films with UV absorption ability.

"Turn on" Fluorescence Sensor of Glutathione Based on Inner Filter Effect of Co-Doped Carbon Dot/Gold Nanoparticle Composites.

Glutathione (GSH) is a thiol that plays a significant role in nutrient metabolism, antioxidant defense and the regulation of cellular events. GSH deficiency is related to variety of diseases, so it is useful to develop novel approaches for GSH evaluation and detection. In this study we used nitrogen and phosphorus co-doped carbon dot-gold nanoparticle (NPCD–AuNP) composites to fabricate a simple and selective fluorescence sensor for GSH detection. We employed the reductant potential of the nitrogen and phosphorus co-doped carbon dots (NPCDs) themselves to form AuNPs, and subsequently NPCD–AuNP composites from Au3+. The composites were characterized by using a range of spectroscopic and electron microscopic techniques, including electrophoretic light scattering and X-ray diffraction. The overlap of the fluorescence emission spectrum of NPCDs and the absorption spectrum of AuNPs resulted in an effective inner filter effect (IFE) in the composite material, leading to a quenching of the fluorescence intensity. In the presence of GSH, the fluorescence intensity of the composite was recovered, which increased proportionally to increasing the GSH concentration. In addition, our GSH sensing method showed good selectivity and sensing potential in human serum with a limit of detection of 0.1 µM and acceptable results.

Photodegradation of Azo Dyes in Sunlight Promoted by Nitrogen–Sulfur–Phosphorus Codoped Carbon Dots

Photodegradation of Azo Dyes in Sunlight Promoted by Nitrogen–Sulfur–Phosphorus Codoped Carbon Dots

Detection of Ferric Ions and Catecholamine Neurotransmitters via Highly Fluorescent Heteroatom Co-Doped Carbon Dots.

Carbon dots (CDs) demonstrate very poor fluorescence quantum yield (QY). In this study, with the help of a hydrothermal method, we combined CDs with nitrogen and phosphorus elements belonging to the VA group (in the periodic table) to form heteroatom co-doped CDs, i.e., nitrogen and phosphorus co-doped carbon dots (NPCDs). These displayed a significant improvement in the QY (up to 84%), which was as much as four times than that of CDs synthesized by the same method. The as-prepared NPCDs could be used as an “off-on” fluorescence detector for the rapid and effective sensing of ferric ions (Fe3+) and catecholamine neurotransmitters (CNs) such as dopamine (DA), adrenaline (AD), and noradrenaline (NAD). The fluorescence of NPCDs was “turned off” and the emission wavelength was slightly red-shifted upon increasing the Fe3+ concentration. However, when CNs were incorporated, the fluorescence of NPCDs was recovered in a short response time; this indicated that CN concentration could be monitored, relying on enhancing the fluorescence signal of NPCDs. As a result, NPCDs are considered as a potential fluorescent bi-sensor for Fe3+ and CN detection. Particularly, in this research, we selected DA as the representative neurotransmitter of the CN group along with Fe3+ to study the sensing system based on NPCDs. The results exhibited good linear ranges with a limit of detection (LOD) of 0.2 and 0.1 µM for Fe3+ and DA, respectively.

Design of long-wavelength emission carbon dots for hypochlorous detection and cellular imaging

A facile strategy for the preparation of nitrogen and phosphorus co-doped carbon dots (N, P-CDs) with long-wavelength emission is attractively proposed in one-pot hydrothermal strategy. The resulting N, P-CDs hold exceptional optical features and display excitation wavelength-independent properties with the emission wavelength at 590 nm, which enable it with the satisfactory relative quantum yield (QY) of 15.6% in long-wavelength region. In addition, the proposed N, P-CDs demonstrates specific selectivity towards ClO− over other competitive reactive oxygen species and exhibits rapid fluorescence response time to ClO−. Moreover, the N, P-CDs exhibits low-cytotoxicity and excellent cell membrane permeability for recognizing ClO− in SMMC-7721 cells, which demonstrates their enormous potential in biological system.

Nitrogen and Phosphorus Co-Doped Carbon Dots for Selective Detection of Nitro Explosives.

In this work, a highly selective and sensitive method has been developed for the detection of trinitrophenol (TNP), which is a dangerous explosive. For this purpose, N and P co-doped carbon dots (NP-Cdots) have been used. Synthesis of N and P co-doped carbon dots has been carried out by a simple and quick method. X-ray photoelectron spectroscopy analysis was carried out to detect the doping of N and P. These carbon dots are insoluble in water (inNP-Cdots). These carbon dots were functionalized by treating them with conc. HNO3 so that they become water-soluble (wsNP-Cdots). These dots were characterized by different analytical techniques such as IR, UV–vis, and fluorescence spectroscopy. The as-prepared wsNP-Cdots have good fluorescence properties. The average diameter of wsNP-Cdots is found to be 5.7 nm with an interlayer spacing (d-spacing) of 0.16 nm. The as-prepared wsNP-Cdots are highly sensitive and selective toward TNP, as observed using a fluorescence quenching technique. The quenching constant for TNP is found to be very high (8.06 × 104 M–1), which indicates its high quenching ability. The limit of detection is found to be 23 μM.

An easy synthesis of nitrogen and phosphorus co-doped carbon dots as a probe for chloramphenicol.

Heteroatom doping in carbon dots (CDs) was found to be an efficient way to regulate the structure of electronic energy levels and enhance the fluorescence characteristics of CDs. Nevertheless, most reported fabrication processes of heteroatom-doped CDs are rigorous and complex. Herein, a facile and novel strategy was developed to rapidly prepare nitrogen and phosphorus co-doped CDs (N,P-CDs) using acetic acid as the carbon source, and arginine, 1,2-ethylenediamine (EDA) and diphosphorus pentoxide as the dopants, respectively. The optical, morphological and structural characterizations of the synthesized N,P-CDs were investigated via UV and photoluminescence spectroscopy, X-ray photoelectron spectroscopy, TEM, and FT-IR spectroscopy. The N,P-CDs display outstanding fluorescence stability under high ionic strength (1.6 M KCl), and long time UV irradiation, indicating that they can be used as favorable candidates for fluorescent probes. The fluorescence of N,P-CDs was selectively quenched by chloramphenicol (CAP) with a short response time. The linear range of the response to CAP was from 0.8 to 70 μM with a limit of detection of 0.36 μM (S/N = 3). Notably, the fabricated N,P-CDs were employed for the highly selective and sensitive detection of CAP in milk samples, indicating their potential applications in biologically related areas.