Project description:A facile, economical, and one-step hydrothermal method was used to prepare highly luminescent nitrogen-doped carbon quantum dots (N-CQDs) with chitosan as both carbon and nitrogen sources. The as-prepared N-CQDs have an average size of 2 nm and exhibit excitation wavelength-dependent fluorescence with a maximum excitation and emission at 330 and 410 nm, respectively. Furthermore, due to the effective quenching effect of Fe3+ ions, the prepared N-CQDs can be used as a fluorescent sensor for Fe3+ ion-sensitive detection with a detection limit of 0.15 μM. The selectivity experiments revealed that the fluorescent sensor is specific to Fe3+ even with interference by high concentrations of other metal ions. Most importantly, the N-CQD-based Fe3+ ion sensor can be successfully applied to the determination of Fe3+ in real water samples. With excellent sensitivity and selectivity, such stable and cheap carbon materials are potentially suitable for the monitoring of Fe3+ in environmental application.
Project description:The current research mainly focuses on transforming low-quality waste into value-added nanomaterials and investigating various ways of utilising them. The hydrothermal preparation of highly fluorescent N-doped carbon dots (N-CDs) was obtained from the carboxymethylcellulose (CMC) of oil palm empty fruit bunches and linear-structured polyethyleneimines (LPEI). Transmission electron microscopy (TEM) analysis showed that the obtained N-CDs had an average size of 3.4 nm. The N-CDs were monodispersed in aqueous solution and were strongly fluorescent under the irradiation of ultra-violet light. A detailed description of the morphology and shape was established using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was shown that LPEI were successfully tuned the fluorescence (PL) properties of CDs in both the intrinsic and surface electronic structures, and enhanced the quantum yield (QY) up to 44%. The obtained N-CDs exhibited remarkable PL stability, long lifetime and pH-dependence behaviour, with the excitation/emission maxima of 350/465.5 nm. Impressively, PL enhancement and blue-shifted emission could be seen with the dilution of the original N-CDs solution. The obtained N-CDs were further applied as fluorescent probe for the identification of Cu2+ in aqueous media. The mechanism could be attributed to the particularly high thermodynamic affinity of Cu2+ for the N-chelate groups over the surface of N-CDs and the fast metal-to-ligand binding kinetics. The linear relationship between the relative quenching rate and the concentration of Cu2+ were applied between 1-30 µM, with a detection limit of 0.93 µM. The fluorescent probe was successfully applied for the detection of Cu2+ in real water. Moreover, a solid-state film of N-CDs was prepared in the presence of poly (vinyl alcohol) (PVA) polymer and found to be stable even after 72-h of continuous irradiation to UV-lamp. In contrast to the aqueous N-CDs, the composite film showed only an excitation independent property, with enhanced PL QY of around 47%. Due to the strong and stable emission nature of N-CDs in both aqueous and solid conditions, the obtained N-CDs are ideal for reducing the overall preparation costs and applying them for various biological and environmental applications in the future.
Project description:Fluorescent carbon quantum dots (CQDs) have held great promise in analytical and environmental fields thanks to their congenitally fascinating virtues. However, low quantum yield (QY) and modest fluorescent stability still restrict their practical applications. In this investigation, a green hydrothermal strategy has been devised to produce water-soluble nitrogen/phosphorus (N/P) co-doped CQDs from edible Eleocharis dulcis with multi-heteroatoms. Without any additives and further surface modifications, the resultant CQDs exhibited tunable photoluminescence just by changing hydrothermal temperatures. Appealingly, they showed remarkable excitation-dependent emission, high QY, superior fluorescence stability, and long lifetime. By extending the CQDs solutions as a "fluorescent ink", we found their potential application in the anti-counterfeit field. When further evaluated as a fluorescence sensor, the N/P co-doped CQDs demonstrated a wide-range determination capability in inorganic cations, and especially the remarkable sensitivity and selectivity for elemental Fe3+. More significantly, the green methodology we developed here can be readily generalized for scalable production of high-quality CQDs with tunable emission for versatile applications.
Project description:Fluorescent carbon nanomaterials have attracted increasing attention owing to their unique photoluminescence properties, good biocompatibility and low toxicity in bioimaging as well as biosensing. Heteroatom doping is usually used to improve photoluminescence properties by tuning the functional groups and the particle size domain effect, thus leading to redshifted emission. Here, we report a straightforward strategy for the fabrication of a mixture of fluorescent phosphorus and nitrogen carbon nanodots (P,N-CDs) followed by separating two kinds of fluorescent fractions based on their different negative charges. Such a one-pot hydrothermal method using formamide, urea and hydroxyethylidene diphosphonic acid as the precursor yields fluorescent P,N-CDs. Specifically, blue-emitting CDs (bCDs) and green-emitting CDs (gCDs) were separated by using column chromatography. The quantum yields of bCDs and gCDs were 20.33% and 1.92%, respectively. And the fluorescence lifetimes of bCDs and gCDs were 6.194 ns and 2.09 ns, respectively. What is more, the resultant P,N-CDs exhibited low toxicity and excellent biocompatibility. Confocal fluorescence microscopy images were obtained successfully, suggesting that P,N-CDs have excellent cell membrane permeability and cellular imaging. This work provides a promising fluorescent carbon nanomaterial with tunable emission as a probe for versatile applications in bioimaging, sensing and drug delivery.
Project description:Here, a simple one-step hydrothermal-assisted carbonization process was adopted for the preparation of nitrogen/phosphorous-doped carbon dots from a water-soluble polymer, poly 2-(methacryloyloxy)ethyl phosphorylcholine (PMPC). By the free-radical polymerization method, PMPC was synthesized using 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and 4,4'-azobis (4-cyanovaleric acid). The water-soluble polymers, PMPC, that have nitrogen/phosphorus moieties are used to prepare carbon dots (P-CDs). The resulting P-CDs were thoroughly characterized by various analytical techniques such as field emission-scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS), high-resolution transmittance electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible (UV-vis) spectroscopy and fluorescence spectroscopy to determine their structural and optical properties. The synthesized P-CDs displayed bright/durable fluorescence, were stable for long periods, and confirmed the enrichment of functionalities including oxygen, phosphorus, and nitrogen heteroatoms in the carbon matrix. Since the synthesized P-CDs showed bright fluorescence with excellent photostability, excitation-dependent fluorescence emission, and excellent quantum yield (23%), it has been explored as a fluorescent (security) ink for drawing and writing (anti-counterfeiting). Further, cytotoxicity study results advised for biocompatibility and thus were used for cellular multicolor imaging in nematodes. This work not only demonstrated the preparation of CDs from polymers that can be used as advanced fluorescence ink, a bioimaging agent for anti-counterfeiting, and cellular multicolor imaging candidate, but additionally prominently opened a new perspective on the bulk preparation of CDs simply and efficiently for various applications.
Project description:The work describes the synthesis and in vivo application of heterotrimetallic complexes of the type {Gd(H2O)[(M(H2O)(CO)3)2(1)]} {1 = DTPA-bis(histidyl-amide); M = Re (3a); (99m)Tc (3b)} for dual modality MR/SPECT imaging. Here, the DTPA-bis(histidylamide) conjugate functions as a trinucleating chelate incorporating Gd in the DTPA core with Re or (99m)Tc in the pair of histidylamide side arms. The two complexes are chemically equivalent as revealed by HPLC, and their "cocktail mixture" (3a + 3b) has demonstrated itself to be essentially a single bimodal imaging probe. The present system has thus overcome the sensitivity difference problem between MRI and SPECT and paved the way for practical applications.
Project description:In this study, sustainable, low-cost, and environmentally friendly biomass (Terminalia chebula) was employed as a precursor for the formation of nitrogen-doped carbon dots (N-CDs). The hydrothermally assisted Terminalia chebula fruit-derived N-CDs (TC-CDs) emitted different bright fluorescent colors under various excitation wavelengths. The prepared TC-CDs showed a spherical morphology with a narrow size distribution and excellent water dispensability due to their abundant functionalities, such as oxygen- and nitrogen-bearing molecules on the surfaces of the TC-CDs. Additionally, these TC-CDs exhibited high photostability, good biocompatibility, very low toxicity, and excellent cell permeability against HCT-116 human colon carcinoma cells. The cell viability of HCT-116 human colon carcinoma cells in the presence of TC-CDs aqueous solution was calculated by MTT assay, and cell viability was higher than 95%, even at a higher concentration of 200 μg mL-1 after 24 h incubation time. Finally, the uptake of TC-CDs by HCT-116 human colon carcinoma cells displayed distinguished blue, green, and red colors during in vitro imaging when excited by three filters with different wavelengths under a laser scanning confocal microscope. Thus, TC-CDs could be used as a potential candidate for various biomedical applications. Moreover, the conversion of low-cost/waste natural biomass into products of value promotes the sustainable development of the economy and human society.
Project description:Green-fluorescent N-doped carbon dots (N-CDs) have been successfully fabricated using hydrothermal treatment of tyrosine and urea. The N-CDs obtained showed excitation-independent emission, superior stability and strong photoluminescence with a quantum yield of ca. 9.8%. Based on these striking behaviors, the as-prepared N-CDs have been utilized in Co2+ detection and temperature sensing. Due to an inner filter effect, the N-CDs obtained were dramatically quenched by Co2+ with linear ranges of 0.1 μM-10 μM, 25 μM-275 μM and 300 μM-400 μM, and they had a detection limit of 0.15 μM. The use of the as-prepared N-CDs has been extended to visualize Co2+ fluctuations in living cells. Additionally, the N-CDs obtained have also been applied for use as a temperature sensor with a linear range of 25-80 °C.
Project description:Herein, following a circular economy approach, we present the synthesis of luminescent carbon dots via the thermal treatment of chestnut and peanut shells, which are abundant carbon-rich food industry by-products. As-synthesized carbon dots have excellent water dispersibility thanks to their negative surface groups, good luminescence, and photo-stability. The excitation-emission behaviour as well as the surface functionalization of these carbon dots can be tuned by changing the carbon source (chestnuts or peanuts) and the dispersing medium (water or ammonium hydroxide solution). Preliminary in vitro biological data proved that the samples are not cytotoxic to fibroblasts and can act as luminescent probes for cellular imaging. In addition, these carbon dots have a pH-dependent luminescence and may, therefore, serve as cellular pH sensors. This work paves the way towards the development of more sustainable carbon dot production for biomedical applications.
Project description:With the discovery of research, many properties of carbon dots are getting better and better. People have taken advantage of this and utilized them interspersed in various fields. In the present study, water-soluble nitrogen-doped carbon dots (N-CDs) with excellent optical and fluorescence thermal properties were prepared by the hydrothermal method using 4-dimethylaminopyridine and N,N'-methylenebisacrylamide as precursors. Co2+ has a selective bursting effect on the fluorescence of N-CDs. The fluorescence of N-CDs is selectively burst by Co2+, and the high sensitivity is good in the range of 0-12 μM with a detection limit of 74 nM. In addition, the good temperature response (reversible and recoverable fluorescence in the temperature range of 20~90 °C) and excellent optical properties of the N-CDs also make them new potentials in the field of fluorescent inks and temperature sensing.