Green preparation of carbon dots with different surface states simultaneously at room temperature and their sensing applications

A Facile One-Step Self-Assembly Strategy for Novel Carbon Dots Supramolecular Crystals with Ultralong Phosphorescence Controlled by NH4. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2402236. [PMID: 38970543 DOI: 10.1002/smll.202402236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

A new methodological design is proposed for carbon dots (CDs)-based crystallization-induced phosphorescence (CIP) materials via one-step self-assembled packaging controlled by NH4 +. O-phenylenediamine (o-PD) as a nitrogen/carbon source and the ammonium salts as oxidants are used to obtain CDs supramolecular crystals with a well-defined staircase-like morphology, pink fluorescence and ultralong green room-temperature phosphorescence (RTP) (733.56 ms) that is the first highest value for CDs-based CIP materials using pure nitrogen/carbon source by one-step packaging. Wherein, NH4 + and o-PD-derived oxidative polymers are prerequisites for self-assembled crystallization so as to receive the ultralong RTP. Density functional theory calculation indicates that NH4 + tends to anchor to the dimer on the surface state of CDs and guides CDs to cross-arrange in an X-type stacking mode, leading to the spatially separated frontier orbitals and the through-space charge transfer (TSCT) excited state in turn. Such a self-assembled mode contributes to both the small singlet-triplet energy gap (ΔEST) and the fast inter-system crossing (ISC) process that is directly related to ultralong RTP. This work not only proposes a new strategy to prepare CDs-based CIP materials in one step but also reveals the potential for the self-assembled behavior controlled by NH4 +.

A dynamic Eu(III)-macrocycle served as the turn-on fluorescent probe for distinguishing H2O from D2O

H2O and D2O are an important pair of analogues, and their high-efficient detections are closely related to fields of chemical industry, food processing, semiconductor, environmental monitoring, etc. Because of their extremely similar physical and chemical properties, H2O and D2O can be mutually soluble in any ratios, and it is generally thought that the discrimination of H2O and D2O is an enormous challenge. Herein, upon the fact that vibrational frequency of O-H is greater than O-D, we design a dynamic Eu(III)-macrocycle Eu-2a with two emitters which exhibits the imine bond breakage of macrocycle emitter H2L2a in H2O or D2O, resulting in the turn-on fluorescence of Eu(III) emitter. For their differential fluorescence sensing signals of Eu-2a on three emission bands (433, 500 and 615 nm), the statistical analysis method is employed to produce fully separated fingerprints and thus high-throughput discrimination of 13 common solvents, especially the H2O and D2O. Fluorescent titration experiments by instrumental or smartphone-based analysis method also prove the successful determination of proportional H2O/D2O mixtures together with the good sensitivity and wide linear response range. Moreover, this H2O-triggered fluorescent complex Eu-2a used as the fluorescence ink also shows its potential in information encryption application. This article must be a valuable reference for the areas of lanthanide-based luminescent material, multianalyte detection and information encryption.

Facile preparation of low temperature carbon dots with long-wavelength emission and their sensing applications for crystal violet

Crystal violet (CV) is one of the main components of common fungicides in daily life, which has inhibitory effect on gram-positive bacteria. However, CV remains in the environment for a long time and have potential risk of disease. Therefore, it is necessary to develop effective methods for detecting CV. Low-temperature carbon dots (LT-CDs) are studied to provide a new idea for the development of CDs green preparation technology from the perspective of low energy consumption. In this experiment, LT-CDs with long-wavelength emission were prepared based on the oxidation, cross-linking polymerization and Schiff base reaction using o-phenylenediamine and hydroquinone as carbon source at low temperature, and were characterized by various techniques. It was found that LT-CDs could be used as a fluorescent probe for quantitative detection of CV based on the inner filter effect, and the practicability of the method was verified by real samples.

Long wavelength emissive ZnO/CQDs phosphor with high color purity and its application in sensitive detection of cadmium (II)

Production of color-tunable emission via simple method for upcoming displays and lighting technologies, and their exceptional luminescence provide considerable potential in sensing application. As environmental pollution and diseases brought by cadmium have always been global issues, therefore, it is imperative to develop an inexpensive, quick, easy, and selective approach for detecting trace cadmium. Herein, we describe the preperation of ZnO/carbon quantum dots (ZnO/CQDs) nanocomposite that emits strongly in the yellow-orange zone with the chromaticity coordinates (0.51, 0.47) and a high color purity (CP) value of 94.3%. The as-produced ZnO/CQDs are used as a fluorescence sensor for Cd2+ via quenching mechanism due to competitive coordination between ZnO/CQDs and Cd2+ with the limit of detection (LOD) of 0.14 μM. Additionally, the suggested method can successfully detect Cd2+ in water samples, demonstrating the feasibility and potential uses of the sensing platform. This study may pave the way for the development of environmentally safe, high-performing, and inexpensive color-tunable phosphor for white LEDs and sensing applications.

Fluorescence detection of 4-nitrophenol and α-glucosidase activity based on 4-nitrophenol-regulated fluorescence of silicon nanoparticles

A fluorescence assay for the detection of 4-nitrophenol (4-NP), α-glucosidase (α-Glu) activity and α-Glu inhibitors (AGIs) is developed based on the inner filter effect (IFE), a flexible and simple signal transfer strategy. In this assay, silicon nanoparticles (Si NPs) synthesized under mild and easily accessible conditions are employed as fluorescent indicators. 4-NP efficaciously quenches the fluorescence of Si NPs through the IFE at a very rapid rate, thus achieving 4-NP detection in a mix-to-read manner, which is suitable for on-site detection. The quenching mechanism has been comprehensively studied and confirmed. More significantly, based on the fact that 4-NP can be generated through α-Glu-catalyzed hydrolysis of 4-nitrophenyl-α-D-glucopyranoside (NPG), the fluorescence detection of α-Glu activity is legitimately achieved by employing NPG as the substrate. The linear ranges for 4-NP and α-Glu activity detection are 0.5-60 μM and 0.5-60 mU mL-1 with low detection limits of 0.074 μM and 0.094 mU mL-1, respectively. This method not only can preciously assay targets in real samples, but is also capable of screening AGIs as drugs as well as assessing their inhibition efficiency.

Gram-Scale Room-Temperature Synthesis of Solid-State Fluorescent Carbon Nanodots for Bright Electroluminescent Light Emitting Diodes

The reaction conditions of high temperature and high pressure will introduce structural defects, high energy consumption, and security risks, severely hindering the industrial application of organic carbon nanodots (CDs). Moreover, the aggregation caused quenching effect also fundamentally limits the CDs based electroluminescent light emitting diodes (LEDs). Herein, for the first time, a rapid one-step room temperature synthetic strategy is introduced to prepare highly emissive solid-state-fluorescent CDs (RT-CDs). A strong oxidizing agent, potassium periodate (KIO₄ ), is adopted as a catalyst to facilitate the cyclization of o-phenylenediamine and 4-dimethylamino phenol in aqueous solution at room temperature for only 5 min. The resultant organic molecule, 2-(dimethylamino) phenazine, will self-assemble kinetically to generate supramolecular-structure CDs during crystallization. The elaborately arranged supramolecular structure (J aggregates) endows CDs with intense solid-state-fluorescence. Density functional theory (DFT) calculation shows that the excited state of RT-CDs exhibits charge transfer characteristic owing to the unique donor-Π-acceptor structure. A high-performance monochrome RT-CDs based electroluminescent LEDs (2967 cd m^-2 and 1.38 cd A^-1 ) were fabricated via systematic optimizations of device engineering. This work provides a concrete and feasible avenue for the rapid and massive preparation of CDs, advancing the commercialization of CDs based optoelectronic devices.

A dual-mode ratiometric fluorescence and smartphone-assisted colorimetric sensing platform based on bifunctional Fe,Co-CQD for glucose analysis at physiological pH

Diabetes is a common and fatal chronic metabolic disease characterized by hyperglycemia, and thus monitoring blood glucose level is essential for early screening and timely control of disease. Herein, we have prepared the bifunctional iron and cobalt co-doped carbon quantum dot (Fe,Co-CQD) with good optical properties and peroxidase-mimetic catalytic activity toward specific substrate o-phenylenediamine (OPD) under alkaline condition. Glucose oxidase (GOx) specifically catalyzes the oxidation of glucose into H₂O₂, and Fe,Co-CQD subsequently triggers a reaction between H₂O₂ and OPD to form yellow product DAP with a distinct UV absorption peak at 420 nm. Simultaneously, the generated DAP also appears a well-defined fluorescence signal at 555 nm, which can suppress the intrinsic fluorescence peak of Fe,Co-CQD (439 nm) owing to the inner filter effect (IFE). Based on this principle, a dual-mode ratiometric fluorescence and colorimetric sensing platform has been constructed for glucose analysis at physiological pH, which reveals the advantages of excellent accuracy, high throughput, simple operation, and low cost. More importantly, a smartphone-assisted colorimetric sensing system based on a portable visual detection kit and a 3D printing smartphone-based device has been constructed, which enables on-site detection of glucose in complex serum samples without laboratory instruments, indicating its potential practical application prospect.

Protective Effects of Zingiberis Carbonisata-Based Carbon Dots on Diabetic Liver Injury in Mice

To explain the active components of ZRC-CDs from the perspective of nanomaterials and investigate the potential mechanism for the treatment of diabetic liver injury, the structure, electron transfer properties, and elemental composition of ZRC-CDs were characterized. The protective effects of ZRC-CDs on the diabetic liver injury were demonstrated using the Alloxan-induced diabetic model. The ZRC-CDs are spherical, with a diameter ranging from 1.0–4.5 nm and a yield of 0.56%. The results showed that ZRC-CDs decreased the levels of blood glucose in diabetic mice and had a mitigating effect on elevated ALT and AST. More studies found that ZRC-CDs were able to decrease the levels of inflammatory cytokines and suppress the protein expression in related signaling pathways.

Mechanisms behind multicolor tunable Near-Infrared triple emission in graphene quantum dots and ratio fluorescent probe for water detection

Developing environmental-friendly and low-cost strategies of synthesizing red-emission graphene quantum dots (R-GQDs) is a considerable challenge. Herein, we present the green and facile preparation of R-GQDs by using o-phenylenediamine (o-PD) and catechol as precursors via oxidation/polymerization and Schiff base reaction at low temperature (80 °C) for 3 hrs. Results show that the prepared R-GQDs exhibit triple fluorescence emissions, which is enabled by the introduce of different nitrogen (pyrrolic N, pyridinic N, and amino N) species on the surface of R-GQDs. Moreover, the R-GQDs are implemented to detect the moisture in different organic solvent. A highly sensitive ratiometric sensing of water in organic solvents is achieved, and the relationship between the change of fluorescence signal caused by moisture and the corresponding internal emission site is also determined. In the end, the multicolor light emissions of R-GQDs are realized by simply adjusting the polarity of surrounding solvents. And based on the solvatochromism of R-GQDs, the multicolor solid fluorescent powder and ink are prepared for illumination application. All in all, the above research work presents a novel R-GQDs for wide application in detecting and illumination.

Preparation of yellow emissive nitrogen-doped carbon dots from o-phenylenediamine and their application in curcumin sensing

In this work, o-phenylenediamine (o-PD) and ethanol are used as raw materials, and a simple solvothermal method is used to prepare yellow emissive nitrogen-doped CDs (YNCDs) (with yellow emission λex/λem = 410/555 nm).

A Simple and Sensitive Nanogold RRS/Abs Dimode Sensor for Trace As3+ Based on Aptamer Controlled Nitrogen Doped Carbon Dot Catalytic Amplification

Using citric acid (CA) and ethylenediamine (EDA) as precursors, stable nitrogen-doped carbon dots (CD) nanosols were prepared by microwave procedure and characterized in detail. It was found that CD_Ns catalyze ethanol (Et)-HAuCl₄ to generate gold nanoparticles (AuNPs), which have strong surface plasmon resonance, Rayleigh scattering, (RRS) and a surface plasmon resonance (SPR) absorption (Abs) effect at 370 nm and 575 nm, respectively. Compled the new catalytic amplification indicator reaction with the specific As³⁺ aptamer reaction, a new RRS/Abs dual-mode aptamer sensor for the assay of trace As³⁺ was developed, based on the RRS/Abs signals increasing linearly with As³⁺ increasing in the ranges of 5-250 nmol/L and 50-250 nmol/L, whose detection limits were 0.8 nmol/L and 3.4 nmol/L As³⁺, respectively. This analytical method has the advantages of high selectivity, simplicity, and rapidity, and it has been successfully applied to the detection of practical samples.

Tunable Organelle Imaging by Rational Design of Carbon Dots and Utilization of Uptake Pathways

Employing one-step hydrothermal treatment of o-phenylenediamine and lysine to exploit their self- and copolymerization, four kinds of CDs (ECDs, NCDs, GCDs, and LCDs) are synthesized, possessing different surface groups (CH₃, C-O-C, NH₂, and COOH) and lipophilicity which endow them with various uptake pathways to achieve tunable organelle imaging. Specifically, highly lipophilic ECDs with CH₃ group and NCDs with C-O-C group select passive manner to target to endoplasmic reticulum and nucleus, respectively. Amphiphilic GCDs with CH₃, C-O-C and NH₂ groups prefer caveolin-mediated endocytosis to locate at Golgi apparatus. Highly hydrophilic LCDs with CH₃, NH₂ and COOH groups are involved in clathrin-mediated endocytosis to localize in lysosomes. Besides, imaging results of cell division, three-dimensional reconstruction and living zebrafish demonstrate that the obtained CDs are promising potential candidates for specific organelle-targeting imaging.