Red-emitting carbon dots prepared from Epipremnum Aureum leaves extract for biological imaging

Red emissive carbon dots’ pressure-triggered aggregation-induced emission enhancement.

Red emissive carbon dots from sucrose (SCD) were synthesized using a facile, isolation-free, one-pot method via microwave pyrolysis. Various passivation agents were used along with sucrose, and a relative change in the chemical and optical properties of the carbon dots was investigated. A detailed systematic study of the effect of various passivations, different solvents, pHs, and temperatures on optical properties was carried out. The influence of excitation wavelength and passivation on photoluminescence (PL) is discussed considering the functional groups associated with the passivating agents. The effect of different solvents on dispersibility and PL behavior has been understood in terms of the dielectric properties of the solvents. The decrease in PL intensity of SCD from pH 3 to 11 facilitates pH sensing. The PL of SCD was found to be essentially stable between the temperature range of 20 and 80 °C. Additionally, the effects of physicochemical properties with respect to passivation, such as charge and surface chemistry in determining the cellular uptake and cytotoxicity, are also addressed. Aside from sensors, the potential of SCDs as bioimaging agents has also been studied for mammalian cells. Moreover, SCD exhibits excellent PL stability investigated under different storage conditions for 15 days.

Luminescent solar concentrators (LSCs) can collect solar light from a large area and concentrate it on their small-area edges mounted with solar cells for efficient solar-to-electricity conversion. Thus, LSCs show huge promise for realizing building-integrated photovoltaics because of their semi-transparency and light weight. However, the low optical efficiency of LSCs becomes a great obstacle for their application in real energy conversion. Herein, yellow emissive carbon dots with a record-breaking ultrahigh quantum yield of up to 86.4% were prepared via a simple hydrothermal approach using low-cost precursors. By combining them with red emissive carbon dots (quantum yield of 17.6%), a large area (∼100 cm2) tandem LSC was fabricated. The power conversion efficiency (PCE) of the large-area carbon dot-integrated tandem LSC reaches up to 3.8%, which is among the best reported in literature for a similar lateral size of LSCs. In particular, the tandem structure based on two laminated layers is novel, and is fit for the real structural application of keeping windows warm, where two glass slides are usually used. The high-efficiency tandem LSC using eco-friendly carbon dots as fluorophores paves way for real applications of LSCs.

Synthesis of multiple-color emitting carbon dots by co-doping of sulfur and nitrogen

Energy transfer (ET) is an effective tool to construct photoelectrochemical (PEC) biosensors for its high sensitivity. Since the materials to develop ET systems are limited, exploring new and universal ET systems is significant. Herein, new photoactive nanosheets (R-CDs NS) formed by self-assembling of red emission carbon dots (R-CDs) have been synthesized, which exhibit wide visible light absorption and stable photocurrent response and have an obvious sensitization effect for TiO2. Gold nanocages (AuNCs), whose absorption overlap well with the R-CDs' emission, were synthesized and served as PEC quenchers for the photosensitized system that consists of TiO2 and R-CDs. The ET between R-CDs and AuNCs can boost the recombination of photogenerated electron-hole pairs of R-CDs and results in a quenched photocurrent of this system. MicroRNA-155 was chosen as a model target. First, the nanocomposite containing R-CDs NS and AuNCs was prepared through DNA modification and hybridization. In the absence of the target, AuNCs and R-CDs were close enough for ET, with TiO2-modified FTO serving as the working electrode, and a quenched photocurrent was detected. In the presence of the target, the disintegration of the nanocomposite was induced through target hybridization and DNA hydrolyzation, leading to the separation of AuNCs and R-CDs NS, and the ET disappeared and led to a high photocurrent. With duplex-specific nuclease enzyme-assisted target recycling, the high sensitivity enabled the sensor to monitor the target in cancer cells. The sensor has a low detection limit of 71 aM. The sensing platform has high sensitivity, good selectivity, and reproducibility.

Carbon dots as a distinctive platform fabricated through a sustainable approach for versatile applications

A novel method for the detection of procalcitonin in a homogeneous system by matched carbon dots (CDs) labeled immunoprobes was proposed based on the principle of FRET and double antibody sandwich method. Blue-emitting carbon dots with a strong fluorescence emission range of 400–550 nm and red-emitting carbon dots with the best excitation range of 410–550 nm were prepared before they reacted with procalcitonin protoclone antibody pairs to form immunoprobes. According to the principles of FRET, blue-emitting carbon dots were selected as the energy donor and red-emitting carbon dots as the energy receptor. The external light source excitation (310 nm) could only cause weak luminescence of CDs. However, once procalcitonin was added, procalcitonin and antibodies would be combined with each other quickly (≤20 min). Here, blue-emitting carbon dots acquired energy could be transferred to red-emitting carbon dots efficiently, causing the emitted fluorescence enhancement of red-emitting carbon dots. The fluorescence detection results in PBS buffer solution and diluted rabbit blood serum showed that the fluorescence intensity variation was linear with the concentration of procalcitonin. There was a good linear relationship between F/F0 and procalcitonin concentrations in PBS buffer solution that ranged from 0 to 100 ng ml−1, and the linear equation was F/F0 = 0.004 * C pct + 0.98359. Detection in the diluted rabbit serum led to the results that were linear in two concentration ranges, including 0–40 ng ml−1 and 40–100 ng ml−1, and the detection limit based on 3σ K−1 was 0.52 ng ml−1. It is likely that this matched CDs labeled immunoprobes system can provide a new mode for rapid homogeneous detection of disease markers.

Oxidation-induced quenching mechanism of ultrabright red carbon dots and application in antioxidant RCDs/PVA film

Red dual-emissive carbon dots for ratiometric sensing of veterinary drugs

In this work, red-emitting carbon dots (R-CDs) with a high quantum yield (QY) of 28% in water were synthesized for the first time by heating an ethanol solution of pulp-free lemon juice. The obtained R-CDs were mono-dispersed with an average diameter of 4.6 nm, and exhibited excitation-independent emission at 631 nm. Meanwhile, these R-CDs featured low cytotoxicity and good photostability, which allow R-CDs to be employed as luminescent probes for in vitro/in vivo bioimaging. In addition, a detailed study on the physical properties and structural compositions of the sodium borohydride (NaBH4) reduced R-CDs with orange emission suggested that surface states on the R-CD surfaces and nitrogen-derived structures in the R-CD cores synergistically caused their intense red luminescence. The low-cost and eco-friendly synthesis method and favorable optical properties of R-CDs make these carbon dots promising for further applications, such as bioimaging and light-emitting diodes.

Red emissive fluorescent carbon dots based on ternary carbon source for imaging α-synuclein fibrils

Photosynthetic-bacteria-derived red emissive carbon dots with low toxicity for lysosomal imaging

Enhanced dual fluorescence quenching of red and blue emission carbon dots by copper dimethyldithiocarbamate for selective ratiometric detection of ziram in foodstuff and water samples

Meticulously designed red emission carbon dots as efficient and stable luminescent species for rapid latent fingerprint recognition and light emitting diodes

Facile synthesis of red-emissive carbon dots with theoretical understanding for cellular imaging