Excitation-independent Emission Research Articles

Dual-emissive carbon dots with high-color purity from sweet basil leaves: synthesis, characterization and optical properties

Abstract In this study, we synthesized dual-emission carbon dots (CDs) from sweet basil leaves dissolved in hexane using the hydrothermal method. Extensive analyses were carried out on their morphology, structure, and optical properties. The CDs show a spherical shape and highly disordered structure with an average diameter of 2 nm. They predominantly comprise carbon surrounded by a dense shell layer of oxygen and nitrogen-related functional groups. Under excitation at a single wavelength of 380 nm, the CDs emit two distinct peaks at 450 and 675 nm demonstrating a narrow bandwidth emission with full width at half maximum (FWHM) of 72 and 27 nm, respectively. The emission characteristics of the CDs are ascribed to the combined effects of radiative recombination of the carbon-core and fully passivated surface states, resulting in two distinct emission peaks and excitation-independent emission property. We present a highly effective and eco-friendly approach approach to fabricate luminescent CDs exhibiting dual emission properties derived from sustainable resources, holding promise for utilization in bioimaging.

Adoption of self-exothermic reaction for synthesis of multifunctional carbon quantum dots: Applications to vincristine sensing and cell imaging

This work introduces an extremely easy method for preparing luminescent carbon dots (CDs) at ambient temperature using 1,2-naphthoquinone sulphonate and ethylenediamine as precursors via self-exothermic reaction without energy input. The as-obtained CDs have a high quantum yield (34.1 %), a production yield of 21.2 %, and a small size diameter (3.44 nm). Various techniques (NMR, TEM, EDX-mapping, XPS, XRD, FT-IR, fluorescence, and UV–visible spectroscopy) were used to characterize the prepared CDs. The CDs exhibited an excitation-independent emission with λex of 275 nm, demonstrating their homogeneity and high purity. The anticancer drug vincristine (VCR) quantitively quenched the fluorescent signal of the synthesized CDs, allowing their application as the first fluorescent nano-sensor to determine VCR. The quenching effect was linear within the range of 0.2–5.0 μg mL−1, enabling the determination of VCR in vials, plasma, and for content uniformity testing with a detection limit of 0.06 μg mL−1. Moreover, the synthesized CDs were employed as a bio-sensing platform to detect VCR in cancer cells owing to their good selectivity, excellent biocompatibility, minimal cytotoxicity, and high stability. The fabrication of CDs with excellent properties at room temperature under mild conditions paves the way for new advancements in the room temperature synthesis of CDs and offers a highly efficient alternative to traditional synthesis approaches.

Human Serum Albumin-Coated 10B Enriched Carbon Dots as Targeted "Pilot Light" for Boron Neutron Capture Therapy.

Boron neutron capture therapy (BNCT) is a physiologically focused radiation therapy that relies on nuclear capture and fission processes. BNCT is regarded as one of the most promising treatments due to its excellent accuracy, short duration of therapy, and low side effects. The creation of novel boron medicines with high selectivity, ease of delivery, and high boron-effective load is a current research topic. Herein, boron-containing carbon dots (BCDs) and their human serum albumin (HSA) complexes (BCDs-HSA) are designed and synthesized as boron-containing drugs for BNCT. BCDs (10B: 7.1 wt%) and BCDs-HSA exhibited excitation-independent orange fluorescent emission which supported the use of fluorescence imaging for tracking 10B in vivo. The introduction of HSA enabled BCDs-HSA to exhibit good biocompatibility and increased tumor accumulation. The active and passive targeting abilities of BCDs-HSA are explored in detail. Subcutaneous RM-1 tumors and B16-F10 tumors both significantly decrease with BNCT, which consists of injecting BCDs-HSA and then irradiating the area with neutrons. In short, this study provides a novel strategy for the delivery of boron and may broaden the perspectives for the design of boron-containing carbon dots nanomedicine for BNCT.

Controlling the optoelectronic properties of nitrogen-doped carbon quantum dots using biomass-derived precursors in a continuous flow system

The synthesis of carbon quantum dots (CQDs) from high molecular weight biomass-derived precursors poses a significant challenge due to the complex molecular structures and low conversion efficiency. This work demonstrates a green, rapid, and sustainable continuous hydrothermal flow synthesis (CHFS) approach for nitrogen-doped carbon quantum dots (NCQDs) from various biomass-derived precursors, including high molecular weight polymeric sources like chitosan, lignin, and humic acid. We find that the precursor structure significantly impacts the size of the fabricated NCQDs and their optical properties. Citric acid, a low molecular weight precursor, yields NCQDs with excitation-independent emission, higher quantum yields, and low non-radiative losses, while NCQDs derived from polymeric precursors exhibit excitation-dependent, red-shifted, and lower efficiency emission. Theoretical calculations, performed to understand the configuration and distribution of nitrogen dopants within the NCQD structure, show that pyridinic and graphitic nitrogen atoms exhibit a strong preference to aggregate near the centre of the edge of the NCQD and not in the vertices nor in the graphitic core, thus affecting the HOMO and LUMO, bandgap, and light absorption and emission wavelengths. The life cycle assessment (LCA) analysis highlights the green and scalable advantages of the CHFS process for producing NCQDs compared to batch methods, making it a sustainable and economically viable approach for large-scale NCQD synthesis from high molecular weight biomass-derived precursors. Hence, the combination of experimental data and theoretical calculations provides a comprehensive understanding of the structure-property relationships in these NCQDs.

Quality by design−aided acid-free synthesis of self P, N, S-doped black seed-derived carbon quantum dots for application as a nanosensor for eltrombopag environmental and bioanalysis and pharmacokinetic assay

Herein, we developed a rapid, one-step, and cost-effective methodology based on the fabrication of water-soluble self-nitrogen, sulfur, and phosphorus co-doped black seed carbon quantum dots (BSQDs) via microwaveirradiation in six minutes. Our synthesis approach is superior to those in the literature as they involved long-time heating (12 h) with sulfuric acid and sodium hydroxide and/or high temperatures (200 °C). A full factorial design was applied to obtain the most efficient synthesis conditions.BSQDs displayed excitation-independent emissions, demonstrating the purity of the synthesized BSQDs, with a maximum fluorescence at 425 nm after excitation at 310 nm. Eltrombopag olamine is an anti-thrombocytopenia drug that is also reported to cause toxicity in river water based on its Persistence, Bioaccumulation, and Toxicity (PBT). The synthesized BSQDs were employed as the first fluorometric sensor for environmental and bioanalysis of eltrombopag. The fluorescence of BSQDs decreased with increasing concentrations of eltrombopag, with excellent selectivity and sensitivity down to 30 ppb. BSQDs were successfully applied as sensing probes for the detection of eltrombopag in medical tablets, spiked and real human plasma samples, and river water samples, with an overall recovery of at least 97 %. The good tolerance to high levels of foreign components and co-administered drugs indicates good selectivity and versatility of the proposed methodology. Plasma pharmacokinetic parameters such as t1/2, Cmax, and t max of eltrombopag were evaluated to be 9.91 h, 16.0 μg mL−1, and 5 h, respectively. Moreover, the green character of the BSQDs as a sensor was proved by various analytical greenness scales.

Highly effective recognition of Fe3+ and lysine based on hydrosoluble N-doped carbon dots

In this study, dual-color nitrogen-doped carbon dots (NCDs) were synthesized using a simple solvothermal method. These fluorescent NCDs displayed excitation-independent emission in red (598 nm in ethanol) and orange (553 nm in water) due to their effect of two different solvents. Both types of NCDs exhibited high stability under UV irradiation for 80 min. The water-soluble NCDs showed excellent sensitivity to Fe3+ ions by the quenching of their photoluminescent (PL) intensity. Quantitative analysis revealed a gradual decline in PL intensity, with a low detection limit of approximately 0.97 µM. Interestingly, the quenched fluorescence of NCDs caused by Fe3+ could be restored by the addition of lysine to the (NCDs + Fe3+) solution, with an estimated detection limit of about 0.37 µM. This phenomenon could be explained in the terms of non-radiative electron/hole recombination, leading to aggregation through efficient photo-induced electron transfer (PET). Utilizing their high selectivity and sensitivity, these NCDs served as “On-Off-On” switches and were successfully employed for the detection of Fe3+ in real water samples, contributing to environmental safety and control efforts.

White-light clusteroluminescence of poly(β-hydroxyvinyl N-substituted carbamate)s via through-space interactions

White-light-emitting polymers have attracted considerable attention in the fields of solid-state lighting and flexible displays. However, achieving white light emission from single-component polymers, particularly in clusteroluminescence (CL) polymers, remains a significant challenge. Herein, we synthesize three non-conjugated luminescent poly(β-hydroxyvinyl N-substituted carbamate)s (PHNCs): PHNCs-C with steric cyclohexyl groups, PHNCs-E with side hydroxyethyl groups, and PHNCs-H with flexible n-hexyl carbon chains. All PHNCs show excitation-independent emission, which transitions to excitation-dependent emission as the excitation wavelengths increase. It is proposed that these emissions originate from the π*→n transition of carbamate in hydroxyurethane and CL of hydroxyurethane, respectively. PHNCs-C exhibits the strongest CL and possesses the highest quantum yield (17.9 %) in solution, a performance that surpasses both PHNCs-E and PHNCs-H. This finding implies that a rigid structure can enhance and stabilize the through-space interactions (TSIs) of hydroxyurethane groups, resulting in a wide cluster-size distribution and white-light emission. Theoretical calculations corroborate these experimental results, further revealing that TSIs occur between the oxygen atoms of hydroxyurethane groups, namely, through-space n-n interactions of oxygen atoms. This work not only provides valuable insights into the nature of CL and TSIs, but also offers a novel approach to preparing single-component white-light-emitting CL polymers.

Biocidal polymer derived near white light-emitting polymeric carbon particles for antibacterial and bioimaging applications.

A growing antimicrobial crisis has increased demand for antimicrobial materials. It has become increasingly popular to convert polymeric macromolecules into polymeric carbon particles (PCP) in order to achieve highly biocompatible materials with unique properties as a result of the ability to synthesize nanomaterials of the right size and add value to existing stable polymers. This work presents the tuning of PCP for antibacterial application by combining a biocidal polymer with one-pot solvothermal synthesis. PCP displayed broad-spectrum antibacterial activity via various mechanisms, including inhibition of bacterial cell walls, ROS generation, and antibiotic resistance. Furthermore, these biocidal PCP were observed to show excitation-independent near-white light emission which on the other hand is generally possible due to mixed sizes, doping, and surface effects. As opposed to the parent biocidal polymer, PCP added ROS-mediated bactericidal activity, increased cytocompatibility, and nanofibers with anti-adhesive effects and potential of imaging bacterial cells.

Highly emissive blue graphene quantum dots with excitation-independent emission via ultrafast liquid-phase photoreduction.

Graphene oxide quantum dots (GOQDs) are promising candidates for biomedical applications since they have lower toxicity and higher biocompatibility than traditional semiconductor quantum dots. However, oxygen functional groups such as epoxy and hydroxyl groups usually induce nonradiative relaxation, which leads to GOQDs exhibiting nonemissive properties. For the enhancement of the emission efficiency of GOQDs, the number of nonradiative relaxation sites should be reduced. This paper reports the synthesis of highly luminescent reduced GOQDs prepared by liquid-phase photoreduction (LPP-rGOQDs). First, GOQDs was fabricated from single-walled carbon nanotubes through chlorate-based oxidation and separation after acoustic cavitation. Subsequently, LPP-rGOQDs were obtained by liquid-phase photoreduction of the GOQD suspension under intense pulsed light irradiation. Liquid-phase photoreduction selectively reduced epoxy groups present on the basal plane of GOQDs, and hydrogenated the basal plane without removal of carbonyl and carboxyl groups at the edges of the GOQDs. Such selective removal of oxidative functional groups was used to control the reduction degree of GOQDs, closely related to their optical properties. The optimized LPP-rGOQDs were bright blue in color and showed quantum yields up to about 19.7%, which was 10 times the quantum yield of GOQDs. Furthermore, the LPP-rGOQDs were utilized to image a human embryonic kidney (HEK293A), and a low cytotoxicity level and satisfactory cell imaging performance were observed.

Nitrogen- and Sulfur-Codoped Strong Green Fluorescent Carbon Dots for the Highly Specific Quantification of Quercetin in Food Samples.

Carbon dots (CDs) doped with heteroatoms have garnered significant interest due to their chemically modifiable luminescence properties. Herein, nitrogen- and sulfur-codoped carbon dots (NS-CDs) were successfully prepared using p-phenylenediamine and thioacetamide via a facile process. The as-developed NS-CDs had high photostability against photobleaching, good water dispersibility, and excitation-independent spectral emission properties due to the abundant amino and sulfur functional groups on their surface. The wine-red-colored NS-CDs exhibited strong green emission with a large Stokes shift of up to 125 nm upon the excitation wavelength of 375 nm, with a high quantum yield (QY) of 28%. The novel NS-CDs revealed excellent sensitivity for quercetin (QT) detection via the fluorescence quenching effect, with a low detection limit of 17.3 nM within the linear range of 0-29.7 μM. The fluorescence was quenched only when QT was brought near the NS-CDs. This QT-induced quenching occurred through the strong inner filter effect (IFE) and the complex bound state formed between the ground-state QT and excited-state NS-CDs. The quenching-based detection strategies also demonstrated good specificity for QT over various interferents (phenols, biomolecules, amino acids, metal ions, and flavonoids). Moreover, this approach could be effectively applied to the quantitative detection of QT (with good sensing recovery) in real food samples such as red wine and onion samples. The present work, consequently, suggests that NS-CDs may open the door to the sensitive and specific detection of QT in food samples in a cost-effective and straightforward manner.

Zinc(II)-Based Ring-and-Rod Coordination Layer as an Excitation-Wavelength-dependent Dual-Emissive Chemosensor for Discriminating Fe3+, Cr3+, and Al3+ in Water.

The reactions of Zn(NO3)2, 3,6-bis(pyridin-3-yl)-9H-carbazole (bpycz), and 2,5-dihydroxyterephthalic acid (H4dhbdc) or 2-bromoterephthalic acid (Br-1,4-H2bdc) under hydro(solvo)thermal conditions yielded corresponding coordination polymers (CPs) {[Zn(H2dhbdc)(bpycz)]•0.5H2O}n (1) and [Zn(Br-1,4-bdc)(bpycz)]•2DMAc•H2O (2), respectively, with high thermal stability approaching 350 °C. CP 1 adopts a ring-and-rod layer structure, which is topologically described as a 4-connected net with the point symbol of 2•65. Two layers are interpenetrated in parallel interlocking mode to form a double 2D → 2D polyrotaxane entanglement with extra-framework void space of 19.6%. CP 2 has a non-interpenetrating ring-and-rod layer structure of 4-connected 2•65 net topology, with extra-framework void space of 16.6%. Thermally activated 1 and 2 revealed CO2 uptakes of 101.1 and 98.6 cm3 g-1, respectively, at P/P0 = 1 and 195 K. X-ray powder diffraction (XRPD) patterns confirmed that 1 and 2 both possessed high chemical stability in H2O, CH3OH, acetone, and DMF, and framework stability during gas adsorption-desorption. The H2O suspension of 1 displayed excitation-dependent dual-emissive properties, appearing at 432 nm upon excitation at 300 nm and at 528 nm upon excitation at 365 nm. Of note, 1 was capable of detection of Fe3+, Cr3+, and Al3+ ions in H2O, showing good anti-interference ability, excellent selectivity, and high sensitivity. More interesting, the dual-emissive properties make 1 to be an excellent luminescence chemosensor to screen Fe3+, Cr3+, and Al3+ from a pool of metal ions in H2O upon excitation at 300 nm via luminescence quenching effect and then discriminate Fe3+, Cr3+, and Al3+ upon excitation at 365 nm via luminescence quenching, unaltered, and enhancement responses, respectively. On the other hand, the H2O suspension of 2 demonstrated an excitation-independent emission appearing at around 430 nm, which could be utilized to sensitively detect Fe3+ and Cr3+ ions with good anti-interference ability and excellent selectivity via luminescence quenching effect. Further, 1 and 2 were recyclability and possessed cycling stability. The plausible sensing mechanisms for 1 and 2 toward Fe3+, Cr3+, and Al3+ were also explored in detail.

Facile Microwave Synthesis of Efficient Green Emissive Carbon Dots Powder and Their Application in Visible Light Communication and White Light Emitting Devices

AbstractHighly green emissive solid‐state carbon dots (CDs) with photoluminescence quantum efficiency of 58% are prepared through a rapid microwave assisted heating method. Due to the spatial confinement from the biuret crystal matrix, aggregation among CDs is effectively suppressed, thus allowing the CDs to give efficient emission in the solid‐state. The CDs show excitation independent emission and mono‐exponential decay characteristics with a nearly constant lifetime of ≈13 ns upon varying the detected emissions, indicating the presence of a single type of emissive state in the CDs. Due to their high quantum efficiency and short lifetime, the obtained CDs are applied as the color conversion layer of a near‐ultraviolet micro light‐emitting diode (µLED) chip (405 nm) for visible light communication, achieving a modulation bandwidth of 165 MHz, which is much higher than the bandwidth of the conventional combination of Ce3+‐doped yttrium aluminum garnet phosphor with GaN LED. Moreover, the green emitting solid‐state CDs are applied to fabricate a prototype white LED device, which exhibits good lighting suitability with a color rendering index of 90.6 and a Commission Internationale de L'Eclairage chromaticity coordinates of (0.327, 0.332).

Waste Biomass Originated Biocompatible Fluorescent Graphene Nano-Sheets for Latent Fingerprints Detection in Versatile Surfaces

In recent years, the application of biocompatible and non-toxic nanomaterials for the detection of fingerprints has become the major interest in the forensic sector and crime investigation. In this study, waste chickpea seeds, as a natural resource, were bioprocessed and utilized for the synthesis of non-toxic graphene nano-sheets (GNSs) with high fluorescence. The graphene GNS were synthesized via pyrolysis at high temperatures and were characterized by TEM, XPS, fluorescence and UV-Vis spectroscopy, and FTIR analysis. The GNS exhibited excitation-independent emission at about 620 nm with a quantum yield of over 10% and showed more distinct blue light under a UV lamp. Biocompatibility of the synthesized GNS in terms of cell viability (88.28% and 74.19%) was observed even at high concentrations (50 and 100 mg/mL), respectively. In addition, the antimicrobial properties of the synthesized GNS-based coatings were tested with the pathogenic strain of Bacillus cereus via live/dead cell counts and a plate counting method confirming their biocompatible and antimicrobial nature for their potential use in safe fingerprint detection. The developed chickpea-originated fluorescent GNS-based spray coatings were tested on different surfaces, including plastic, glass, silicon, steel, and soft plastic for the detection of crime scene fingerprints. Results confirmed that GNS can be used for the detection of latent fingerprints on multiple non-porous surfaces and were easy to detect under a UV lamp at 395 nm. These findings reinforce the suggestion that the developed fluorescent GNS spray coating has a high potential to increase sensitive and stable crime traces for forensic latent fingerprint detection on nonporous surface material. Capitalizing on their color-tunable behavior, the developed chickpea-originated fluorescent GNS-based spray coating is ideal for the visual enhancement of latent fingerprints.

Dual-Exciting Central Carbon Nanoclusters for the Dual-Channel Detection of Hemin

Constructing optical nanoprobes with superior performance is highly desirable for sensitive and accurate assays. Herein, we develop a facile room-temperature strategy for the fabrication of green emissive carbon nanoclusters (CNCs) with dual-exciting centers for the dual-channel sensing of hemin. The formation of the CNCs is attributed to the crosslinking polymerization of the precursors driven by the Schiff base reaction between ethylenediamine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Most importantly, the proposed CNCs have a unique excitation-independent green emission (518 nm) with two excitation centers at 260 nm (channel 1) and 410 nm (channel 2). The dual-exciting central emission can serve as dual-channel fluorescence (FL) signals for highly sensitive and reliable detection of hemin based on the inner filter effect. Because of the great spectral overlap difference between the absorption spectrum of hemin and the excitation lights of the CNCs in the two channels, hemin has a different quenching effect on FL emission from different channels. The dual-channel signals of the CNCs can detect hemin in the range of 0.075–10 μM (channel 1) and 0.25–10 μM (channel 2), respectively. These findings not only offer new guidance for the facile synthesis of dual-exciting central CNCs but also establish a reliable sensing platform for the analysis of hemin in complex matrixes.

Synthesis and characterization of carbon dots derived from compounds containing thioureas and thiazole rings

Synthesizing carbon dots (CDs) using therapeutic compounds as precursors is a new trend in the applications of CDs in drug delivery and disease treatment by leveraging the advantages of nanoparticles and therapeutic molecules simultaneously, without the need of further modifications. Compounds containing thioureas and thiazole rings have been extensively studied in biological applications such as antidiabetic, anticancer, antimicrobial, antiviral and antifungal activities. However, the research using such compounds as precursors to synthesize CDs has not been reported. In this study, four types of CDs derived from 1-(benzo[d]thiazol-2-yl)− 3-phenylthiourea (H2PhT), N-ethyl-N′-(4′-methylthiazol-2′-yl) thiourea (H2EMT), N-phenyl-N′-(4′-methylthiazol-2′-yl)thiourea (H2PhMT) or N-methyl-N′-(4′-methylthiazol-2′-yl)thiourea (H2MMT) were successfully prepared and characterized. The UV–vis absorption, fluorescence, and Fourier-transform infrared (FTIR) spectroscopies, atomic force microscopy (AFM), zeta potential measurements and thermogravimetric analysis (TGA) suggested that these four families of CDs are all less than 10 nm. H2PhT-CDs, H2EMT-CDs, and H2PhMT-CDs possess excitation-independent PL emission at around 440 nm, while H2MMT-CDs exhibit excitation-dependent PL emission property. The structural properties of CDs indicate the presence of certain moieties that may be associated with the therapeutic effects of H2PhT, H2EMT, H2PhMT and H2MMT in the corresponding H2PhT-CDs, H2EMT-CDs, H2PhMT-CDs and H2MMT-CDs. Moreover, all four families of CDs possess a slightly positive or negative charge, which benefits their affinities to cells. The results in this study could provide the knowledge in understanding the potential applications of these CDs in the treatment of diabetes, cancer, and infections in future research.

Facile synthesis of efficient red-emissive carbon quantum dots as a multifunctional platform for biosensing and bioimaging

The red-emissive carbon quantum dots (r-CQDs) have gained considerable interest in the field of fluorescence imaging as they can effectively overcome short-wave background interference. However, the development of efficient and simple synthetic pathways for the preparation of r-CQDs with high production yield and fluorescence quantum yield remains a great challenge. Herein, we prepared the intense red-emissive carbon quantum dots (r-CQDs) through one-pot hydrothermal treatment of methylene violet. The morphology and structure of the as-prepared r-CQDs were characterized through transmission electron microscopy, Raman spectra, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. r-CQDs were well dispersed in water with an average size of 2.39 nm. The surface of r-CQDs was full of oxygen-containing functional groups, which contributed to their high solubility in water. Under ultraviolet light (365 nm) irradiation, both the aqueous solution and powder of r-CQDs emitted intense red luminescence. r-CQDs exhibited the excitation-independent emission property with the maximum fluorescence peak at 596 nm. The fluorescence quantum yield of r-CQDs was calculated to be 26.46% in water using rhodamine B as a reference. Due to the significantly different fluorescence intensity in water and organic solvents, r-CQDs could be applied as the fluorescence sensor to quickly detect the trace amounts of water in various organic solvents. Moreover, the fluorescence of r-CQDs showed selective response to hypochlorite (ClO−) through an “on-off” sensing mechanism. The good biocompatibility of r-CQDs was verified by the cell counting kit-8 (CCK-8) method against mouse hepatocellular carcinoma (Hepa 1–6) cells. Finally, the r-CQDs were successfully used in cellular imaging and they were mainly located in the lysosomes of cancel cells. Thus, r-CQDs could be served as a powerful fluorescence nano-platform for biosensing and bioimaging.

Solvothermal preparation of nitrogen and phosphorus-doped carbon dots with PET waste as precursor and its application

PET-based nitrogen and phosphorus-doped Carbon Dots (NP-CDs) was prepared by solvothermal method with PET waste as raw materials. In terms of structure, NP-CDs were spherical structures with an average particle size of 2.8 nm, and its surface contains amino groups. The as-prepared NP-CDs exhibit excitation-independent emission properties from 300 nm to 430 nm, and the optimal excitation and emission wavelength was 340 nm and 460 nm. In terms of application, the as-prepared NP-CDs could be used to a pH sensor in the range of 2.3 to 12.3. When NP-CDs were dispersed in polyvinyl alcohol (PVA) matrix, excellent light blocking films(LBFs) for UV and blue light were obtained. When the ratio of NP-CDs is 14%, it still does not affect the line of sight, and the barrier rate to UV(380 nm) and blue(430 nm) light is as high as 90% and 80%. In addition, the WLED device with a colour coordinate of (0.29,0.32) and a colour temperature of 8022 K can be obtained with the combination of NP-CDs dispersed in PVA matrix and 395 nm LED chips. Carbon Dots was prepared with waste PET as precursor for the construction of pH sensor, light blocking films and WLED. • Waste PET was adopted as precursor for the preparation of eco-friendly Carbon Dots (NP-CDs) • The as-prepared NP-CDs could be used for the pH sensor in the range of 2.3 to 12.3. • NP-CDs can be used for the construction of light blocking films for UV and blue light. • The WLED device can be obtained with the combination of NP-CDs and 395 nm LED chips.

Red-emitting and antibacterial carbon dots for cellular imaging and skin wound healing

Carbon dots (CDs) as a new type of fluorescent nanomaterials have attracted considerable attention from researchers in chemistry, biology, and materials science. Here, we employed a hydrothermal method for synthesis of red-emitting and antibacterial CDs displaying an excitation-independent emission characteristic with a maximum emission intensity at 610 nm (pH 7.4). The synthesised CDs exhibited a high capability for bioimaging in HeLa cells, because of their negligible cytotoxicity and acceptable red photoluminescence. Moreover, the antibacterial activity of CDs against P. aeruginosa was studied and showed a minimum inhibitory concentration (MIC) of 256 μg ml−1. Further experimental results showed the high ability of the CDs to heal skin wounds in the rat model. According to the observations, wound healing in the presence of the CDs was calculated four days faster with 20.48% better performance than the control group.

Preparation of Carbon Dots from PET Waste by One-step Hydrothermal Method and its Application in Light Blocking Films and LEDs.

An environmentally friendly PET-based Carbon Dots (PET-CDs) with excellent fluorescence properties were prepared with waste PET bottle, pyromellitic acid and ammonia water as raw materials by one-step hydrothermal method. The preparation mechanism of PET-CDs was as follows: PET first underwent ammonolysis reaction to produce terephthalic acid diamide and ethylene glycol, and then dehydrated and carbonized with pyromellitic acid to form PET-CDs. The as-prepared PET-CDs exhibit excitation-independent emission properties in the range from 340 to 440nm, and the fluorescence quantum yield is as high as 87.36%. In terms of structure, PET-CDs is a spherical structure with an average particle size of 2.0nm, and its surface contains carboxyl and amino groups. The PET-CDs were dispersed in a PVA matrix to obtain an light blocking films(LBFs) for 250-450nm light with excellent properties, and its transparency for 450-700nm light is good. In addition, PET-CDs was used in the fields of LED, and it was found that the color coordinate for the LED assembled with PET-CDs and 395nm LED chips is (0.55, 0.44) and the correlated color temperature is 2018K.

Lanthanide bimetallic MOF-based fluorescent sensor for sensitive and visual detection of sulfamerazine and malachite

A lanthanide terbium/europium metal–organic framework (Tb0.6Eu0.4-MOF) was prepared by one-step solvothermal method at room temperature. A series of characterizations including scanning electron microscopy, powder X-ray diffraction spectra, Fourier transform infrared spectra and X-ray photoelectron spectroscopy were carried out to clarify the physical characteristics of the synthesized material. The data clarified that the prepared Tb0.6Eu0.4-MOF possessed rod-like morphology with a width of 1–2 μm, and had good crystal structure, good stability, response speed and excitation-independent emission feature. The bunchy Tb0.6Eu0.4-MOF was then used to construct fluorescent sensors for rapid identification of malachite green and sulfamerazine. It was revealed that the detection mechanism was inner filter effect. The effects of different parameters such as excitation wavelength and incubation times were investigated on the fluorescence analysis performance. The data clarified that the optimal excitation wavelength and incubation time was 240 nm and 3 min, respectively. The detection platform exhibited the high sensitivity and selectivity toward malachite green in the linear range of 2–180 μM and determined limit of detection was 1.12 μM. Besides, the proposed sensor allowed sensitive detection of sulfamerazine in the linear range of 2–140 μM with a low detection limit of 0.1 μM. Meaningfully, a smartphone application was designed to assist the proposed sensor to realize visual, intelligent and rapid detection of malachite green and sulfamerazine. Furthermore, the practical application of the proposed sensor has been also verified by high performance liquid chromatography, showing good accuracy, sensitivity and satisfactory recoveries. The results suggested that the Tb0.6Eu0.4-MOF-based ratiometric fluorescent sensor had the potential to become a promising technique for rapid detection of malachite green or sulfamerazine with smartphone application. Therefore, the prepared Tb0.6Eu0.4-MOF is one kind of efficient and cost-effective potential materials for developing fluorescent sensor for rapid, sensitive and selective detection of sulfamerazine and malachite.