User:Aftab2003/sandbox

Carbon quantum dots (CQD) gained significant interest in the research after its discovery since 2006. This review article was very informative and focused on the development as well as application of CQD. In this review, it was cited that, CQD possessed properties like low toxicity, high chemical sensing ability, high chemical stability, high electro catalytic ability, multicolored emission, tune able band gap which might be made smaller or larger, highly performance photo catalyst ability, electrically stability and good conduction ability and environmental friendly .Some of the properties of CQD such as fluorescence was well described and new areas of research was also explored, like the exact mechanism of fluorescence is still debatable because of the defective surface of quantum dots. Surface passivation, functionalization or doping of CQD resulted in the improvement of properties such as excitation wavelength-dependent emission of the dots. In this review, the synthesis of the CQD was described by two ways, the top down route or by bottom up route. The preferred route was that which offered green synthetic route. The CQD were used in the chemical sensing for the organic as well as in the inorganic materials, As a Biosensor, they were used in the detection and identification of materials like proteins ,PBB15, nucleic acids, SNP, exploitation of aptamers, staining of proteins, bacterial counting in water, fluorescent probe for antibacterial drugs like amoxicillin, dopamine. In Bio-imaging, CQD were used both in vivo and in vitro applications. They were more bio-compatible than semiconductors QD. They were used as a probe for hydrogen sulfide gas or for in vivo imaging of copper (II) in living cells. The conjugation, passivation, and functionalization effected the localization of the CQD in the cell as well as their cell up take. In the field of medicine, they were used in a variety of ways, due to their up conversion properties, CQD were used as photosensitizer in photo dynamic therapy, for the treatment of the deep seated cancer cells. In the field of radiotherapy, CQD generated free radicals on the interaction with high energy radiation. These radicals destroyed cancer cells. CQD were used as carrier for the fluorescence tracking or delivering (DOX) of a variety of the drug or gene. They were also used in the photo regulated drug release, pH triggered drug release and in localized tumor therapy. That way, it became possible to customize the drug injection time, drug dosage and drug circulation half life time. In the field of photo catalysis, CQD were doped with metal oxide. These modification offered the way to explore the full spectrum of sunlight due to the enhancement of photo catalytic activity by the photosensitizer CQD. The CQD or its doped form (N-CQD) were also used in the solar cells as photosensitizer in photo voltaic devices. In the field of electro catalysis, CQD or N-CQD could offer the solution for the replacement of the expensive Platinum metal for the OOR or ORR process in fuel cells. Similarly, CQD-NiFe layered double hydroxide composite might be a solution to the sluggish kinetic and the expensive material used in OER. Beside above discussion, there were a number of areas still demand more research like the increase in the quantum yield of CQD, the development of CQD which will be more selective and targeting for cells, establishment of the exact mechanism of cellular uptake of CQD and their toxicological effect on cells. There is requirement of CQD with excitation in Red or NIR region with bright fluorescence emission. New techniques are needed for the development of controlled shaped, sized and functional CQD because the geometry, structure and composition affect their properties. It is also needed to conduct research on the theoretical and experimental usability of CQD or Doped CQD in electro catalysis for ORR, OER. In short, it is needed to conduct research to develop CQD which is simple, low cost, prepared from an efficient route and compete in properties with the already developed material. It should be selective, sensitive in its application.