Ultra-radiant photoluminescence of glutathione rigidified reduced carbon quantum dots (r-CQDs) derived from ice-biryani for in vitro and in vivo bioimaging applications

Current trends in carbon-based quantum dots development from solid wastes and their applications

Urbanization and a massive population boom have immensely increased the solid wastes (SWs) generation and are expected to reach 3.40 billion tons by 2050. In many developed and emerging nations, SWs are prevalent in both major and small cities. As a result, in the current context, the reusability of SWs through various applications has taken on added importance. Carbon-based quantum dots (Cb-QDs) and their many variants are synthesized from SWs in a straightforward and practical method. Cb-QDs are a new type of semiconductor that has attracted the interest of researchers due to their wide range of applications, which include everything from energy storage, chemical sensing, to drug delivery. This review is primarily focused on the conversion of SWs into useful materials, which is an essential aspect of waste management for pollution reduction. In this context, the goal of the current review is to investigate the sustainable synthesis routes of carbon quantum dots (CQDs), graphene quantum dots (GQDs), and graphene oxide quantum dots (GOQDs) from various types SWs. The applications of CQDs, GQDs, and GOQDs in the different areas are also been discussed. Finally, the challenges in implementing the existing synthesis methods and future research directions are highlighted.

Construction of a photo-controlled fluorescent switching with diarylethene modified carbon dots

Photo-controlled fluorescent switching is of great utility in fluorescence sensors, reversible data storage, and logic circuit, based on their modifiable emission intensity and spectra. In this work, a novel photo-controlled reversible fluorescent switching system was constructed based on photochromic diarylethene (DT) molecular modified fluorescent carbon dots (CDs). The fluorescent CDs acted as fluorescent donors and the photochromic diarylethene molecular functioned as acceptors in this fluorescent switching system. The fluorescence modulation efficiency of the fluorescent switching was determined to be 97.1%. The result was attributable to Förster resonance energy transfer between the CDs and the diarylethene molecular. The fluorescent switching could undergo 20 cycles without significant decay.

Activated Carbon and Carbon Quantum Dots/Titanium Dioxide Composite Based on Waste Rice Noodles: Simultaneous Synthesis and Application in Water Pollution Control

To achieve the full utilization of waste rice noodle (WRN) without secondary pollution, activated carbon (AC) and carbon quantum dots/titanium dioxide (CQDs/TiO2) composite were simultaneously synthesized by using WRN as raw material. Both of the two materials showed potential applications in water pollution control. The AC based on WRN displayed a porous spherical micro-morphology, which could absorb heavy metal elements like Pb(II) and Cr(VI) efficiently, with a maximum equilibrium uptake of 12.08 mg·g−1 for Pb(II) and 9.36 mg·g−1 for Cr(VI), respectively. The adsorption of the resulted AC could match the Freundlich adsorption isotherm and the pseudo-second-order kinetics mode. On the other hand, the CQDs/TiO2 composite based on WRN displayed a high efficient photocatalytic degradation effect on various water-soluble dyes such as methylene blue, malachite green, methyl violet, basic fuchsin, and rhodamine B under visible light irradiation, which showed better photocatalytic performance than commercial TiO2. The introduction of CQDs based on WRN to TiO2 could result in efficient electron-hole pair separation and enable more photogenerated electrons to reduce O2 and more photogenerated holes to oxidize H2O or OH−, which could cause stronger abilities in producing O2·− and ·OH radical and better photocatalytic activity.

Research progress in synthesis and biological application of quantum dots

Quantum dots are an excellent choice for biomedical applications due to their special optical properties and quantum confinement effects. This paper reviews the research and application progress of several quantum...

Biomass-Based Carbon Dots: Current Development and Future Perspectives

Carbon dots have been considered as a solution to the challenges that semiconductor quantum dots have encountered because they are more biocompatible and can be synthesized from abundant and nontoxic materials such as biomass. This review will highlight the advantages of these biomass-based carbon dots in terms of synthesis, properties, and applications in the biomedical field. Furthermore, future applications especially in the biomedical field of biomass-based carbon dots as well as the challenges of semiconductor quantum dots such as biocompatibility, photobleaching, environmental challenges, toxicity, and poor solubility will be discussed in detail. Biomass-derived quantum dots, a subsection of carbon dots that are the most desirable for future research, will be focused upon including from synthesis to applications. Finally, the future development of biomass derived quantum dots in the biomedical field will be discussed and evaluated to unlock the potential for their applications.

Green synthesis of white light emitting carbon quantum dots: Fabrication of white fluorescent film and optical sensor applications

In this work, we have reported on the facile synthesis of white light-emitting carbon quantum dots (CQD) from corncob by hydrothermal method. This CQD has a broad emission from 380 nm to 650 nm with high photoluminescence intensity even after three months of shelf-life and stable at variable pH conditions. The presence of Si and N impurities in the biomass gives a greater advantage in producing white light emission with high quantum yield (54%) and enhanced lifetime at ambient conditions. The CQD is highly sensitive towards DNA, paracetamol, Pb²⁺, Cu²⁺, Fe³⁺, and Cr³⁺ fluorescence sensing and signifies its application as a multi-modal fluorescence sensor. The results of optical sensitivity calculated from the linear range of 1-10 ng/mL, 0.10-0.30 mg/mL, 2.5446 ng/mL, 0.0694 mg/mL, 0.3103-1.5515 μM/mL, 0.4299-4.7293 μM/mL, 1.3010 μM/mL and 0.05-2.5 μM/mL. The limit of detection is 2.5446 ng/mL, 0.0694 mg/mL, 0.8641 μM/mL, 1.2454 μM/mL, 1.3010 μM/m, 0.8550 μM/mL and 2.8562 μM/mL, respectively. And also, the relative standard deviation values of 2.30%, 4.46%, 1.79%, 1.84%, 0.26%, 1.23% and 0.35% are evidences its possibility of development towards potential optical sensor applications. Flexible white light-emitting sheets were fabricated from the CQD, illuminates uniform brightness, and has good color reproducibility and higher stability under various UV light excitation.

Group IV nanodots: synthesis, surface engineering and application in bioimaging and biotherapy

Group IV nanodots (NDs) mainly including carbon (C), silicon (Si), germanium (Ge) have aroused much attention as one type of important nanomaterials that are widely studied in optoelectronics, semiconductors, sensors and biomedicine-related fields owing to the low cost of synthesis, good stability, excellent biocompatibility, and some attractive newly emerged properties. In this review, the synthesis, surface engineering and application in bioimaging and biotherapy of group IV NDs are summarized and discussed. The recent progress in the rational synthesis and functionalization, specific therapy-related properties, together with in vivo and in vitro bioimaging are highlighted. Their new applications in biotherapy such as photothermal therapy (PTT) and photodynamic therapy (PDT) are illustrated with respect to C, Si and Ge NDs. The current challenges and future applications of these emerging materials in bioimaging and biotherapy are presented. This review provides readers with a distinct perspective of the group IV NDs nanomaterials for synthesis and surface engineering, and newly emerging properties related to applications in biomedicine.

Sensor and Bioimaging Studies Based on Carbon Quantum Dots: The Green Chemistry Approach

Since carbon quantum dots have high photoluminescent efficiency, it has been a desired material in sensor and bioimaging applications. In recent years, the green chemistry approach has been preferred and the production of quantum dots has been reported in many studies using different precursors from natural, abundant, or waste sources. Hydrothermal, chemical oxidation, microwave supported, ultrasonic, solvothermal, pyrolysis, laser etching, solid-state, plasma, and electrochemical methods have been reported in the literature. In this review article, green chemistry strategies for carbon quantum dot synthesis is summarized and compared with conventional methods using methodologic and statistical data. Furthermore, a detailed discussion on sensor and bioimaging applications of carbon quantum dots produced with green synthesis approaches are presented with a special focus on the last decade.