In recent years, nano carbon quantum dots (CQDs) have received increasing attention due to their properties such as small size, fluorescence emission, chemical stability, water solubility, easy synthesis, and the possibility of functionalization. CQDs are fluorescent 0D carbon nanostructures with sizes below 10 nm. The fluorescence in CQDs originates from two sources, the fluorescence emission from bandgap transitions of conjugated π-domains and fluorescence from surface defects. The CQDs can emit fluorescence in the near-infrared (NIR) spectral region which makes them appropriate for biomedical applications. The fluorescence in these structures can be tuned with respect to the excitation wavelength. The CQDs have found applications in different areas such as biomedicine, photocatalysis, photosensors, solar energy conversion, light emitting diodes (LEDs), etc. The biomedical applications of CQDs include bioimaging, drug delivery, gene delivery, and cancer therapy. The fluorescent CQDs have low toxicity and other exceptional physicochemical properties in comparison to heavy metals semiconductor quantum dots (QDs) which make them superior candidates for biomedical applications. In this review, the synthesis routes and optical properties of the CQDs are clarified and recent advances in CQDs biomedical applications in bioimaging (in vivo and in vitro), drug delivery, cancer therapy, their potential to pass blood–brain barrier (BBB), and gene delivery are discussed.

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Carbon quantum dots and their biomedical and therapeutic applications: a review

Modern trends in the greener synthesis and fabrication of inorganic, organic and coordination compounds, materials, nanomaterials, hybrids and nanocomposites are discussed. Green chemistry deals with synthesis procedures according to its classic 12 principles, contributing to the sustainability of chemical processes, energy savings, lesser toxicity of reagents and final products, lesser damage to the environment and human health, decreasing the risk of global overheating, and more rational use of natural resources and agricultural wastes. Greener techniques have been applied to synthesize both well-known chemical compounds by more sustainable routes and completely new materials. A range of nanosized materials and composites can be produced by greener routes, including nanoparticles of metals, non-metals, their oxides and salts, aerogels or quantum dots. At the same time, such classic materials as cement, ceramics, adsorbents, polymers, bioplastics and biocomposites can be improved or obtained by cleaner processes. Several non-contaminating physical methods, such as microwave heating, ultrasound-assisted and hydrothermal processes or ball milling, frequently in combination with the use of natural precursors, are of major importance in the greener synthesis, as well as solventless and biosynthesis techniques. Non-hazardous solvents including ionic liquids, use of plant extracts, fungi, yeasts, bacteria and viruses are also discussed in relation with materials fabrication. Availability, necessity and profitability of scaling up green processes are discussed.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.191378

Greener synthesis of chemical compounds and materials

A focus to green synthesis of metal/metal based oxide nanoparticles: Various mechanisms and applications towards ecological approach

铜听硫化物(Cu2SnS3 ) 是一个潜在的地球为光电的设备申请的丰富的吸收器材料。在这贡献，有纯作文和大谷物缩放的阶段的三斜晶系的 Cu2SnS3 电影作为先锋用 Cu， Sn 和 S 从一个肼答案过程被制作。吸收测量表明这部 Cu2SnS3 电影把 0.88 eV，和霍尔效果测量的直接光的乐队差距显示电影最后是有 0.86 cm2/Vs. 的洞活动性的 p 类型 Mo/Cu2SnS3/CdS/ZnO/AZO/Au 被生产，完成的最好的设备效率是 0.78% 。另外，这台设备在周围的存储期间显示出改进设备性能。这研究为 Cu2SnS3 太阳能电池的进一步的改进打了一些基础。

Hydrazine processed Cu2SnS3 thin film and their application for photovoltaic devices

Challenges for critical raw material recovery from WEEE - The case study of gallium.

We present a model for the effect of thermal annealing on a single-layer InAs/GaAs quantum dot (QD) heterostructure and study the corresponding variation in full photoluminescence (PL) spectrum. In/Ga interdiffusion due to annealing is modeled by Fickian diffusion and the Schrodinger equation is solved separately for electrons and holes to obtain ground state PL peaks of the heterostructure at different annealing temperatures. We theoretically examine the decrease in strain effects and carrier confinement potentials with annealing. PL spectra of the entire ensemble of QDs, annealed at different temperatures, are calculated from a lognormal distribution of QD heights derived from experimental atomic force microscopy (AFM) data. Results from our calculations, which illustrate the blueshift in emission wavelength and linewidth variation in PL with annealing, are in excellent agreement with experimental PL observations on the same samples. This highlights the potential of the model to assist in precisely engi...

Presentation and experimental validation of a model for the effect of thermal annealing on the photoluminescence of self-assembled InAs/GaAs quantum dots

Numerical study and experimental investigation of zone refining in ultra-high purification of gallium and its use in the growth of GaAs epitaxial layers

Ternary chalcogenide Cu2SnS3 (CTS) thin films are deposited on glass substrates using low cost ultrasonic spray pyrolysis (USP) technique by varying substrate temperatures 300 degrees C to 550 degrees C. Crystal structure of CTS thin film is found to change its phase from amorphous to tetragonal phase with increase in substrate temperature. Properties of as-deposited Cu2SnS3 thin films are studied using various characterization techniques. X-ray powder diffraction (XRD) studies confirm the formation of Cu2SnS3 tetragonal phase with orientation along (112) plane with increase in substrate temperature. Raman analysis revealed the formation of binary phase at 550 degrees C substrate temperature. Increase in substrate temperature resulted in stoichiometric nature of Cu2SnS3 films at 500 degrees C. The absorption coefficient of CTS films is found to be similar to 10(5) cm(-1) with band gap ranging from 1.35 eV to 1.48 eV. Electrical properties of CTS films exhibited p type conductivity with carrier concentration of the order of 10 21 cm(-3). The resistivity of the CTS films is found to vary from 1.5 x 10(-3) to 3.2 x 10(-3) Omega-cm. Photocatalytic effect of optimized Cu2SnS3 thin film under visible light (300 W) is examined with methylene blue (MB) dye and similar to 90% MB is degraded under 3 hours visible light irradiation. The above properties indicate that Cu2SnS3 is a potential candidate to be used for solar cell absorber layer and photocatalytic activity.

Temperature dependent growth of Cu2SnS3 thin films using ultrasonic spray pyrolysis for solar cell absorber layer and photocatalytic application

This study addresses the cellular uptake of nanomaterials in the field of bio-applications. In the present study, we have synthesized water-soluble lead sulfide quantum dot (PbS QD) with glutathione and 3-MPA (mercaptopropionic acid) as the stabilizing ligand using a green approach. 3-MPA-capped QDs were further modified with streptavidin and then bound to biotin because of its high conjugation efficiency. Labelling and bio-imaging of cells with these bio-conjugated QDs were evaluated. The bright red fluorescence from these types of QDs in HeLa cells makes these materials suitable for deep tissue imaging.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.171614

Water-mediated green synthesis of PbS quantum dot and its glutathione and biotin conjugates for non-invasive live cell imaging.

An approach to suppress the blue-shift of photoluminescence peaks in coupled multilayer InAs/GaAs quantum dots by high temperature post-growth annealing

Kaustab Ghosh

Papers

Presentation and experimental validation of a model for the effect of thermal annealing on the photoluminescence of self-assembled InAs/GaAs quantum dots

Numerical study and experimental investigation of zone refining in ultra-high purification of gallium and its use in the growth of GaAs epitaxial layers

Temperature dependent growth of Cu2SnS3 thin films using ultrasonic spray pyrolysis for solar cell absorber layer and photocatalytic application

Water-mediated green synthesis of PbS quantum dot and its glutathione and biotin conjugates for non-invasive live cell imaging.

An approach to suppress the blue-shift of photoluminescence peaks in coupled multilayer InAs/GaAs quantum dots by high temperature post-growth annealing