High Pressure Study On Optical Properties Of Carbon Dots

Carbon dots have drawn significant attention due to their excellent and unique physical and chemical properties,such as ease of modification,outstanding water solubility and biocompatibility and so on.Therefore,CDs has a broad application prospect in biological imaging,laser catalyst,biochemical sensing,light-emitting diode,solar cell and other fields.They have become a hot topic in the research field of fluorescent nanomaterials.In the past few years,the research on the synthesis,properties and application of CDs have progressed rapidly and many research groups have carried out relevant research.However,it is difficult to have a clear understanding of the relationship between the structure and optical properties of CDs due to their numerous precursors and complex structures.Therefore,elucidation of their photoluminescence mechanism not only is a very important theoretical guiding significance for the research and development of CDs,but also can effectively promote the development of new theories in the field of nanometer to some extent.At present,for the study of CDs,many literature studies have reported that their PL is related to their sizes,molecular states,zigzag sites,defect states,surface states and conjugated systems.Although great success has been achieved,the relationship between the photoluminescence mechanism of CDs and their special chemical structure is still not clear.Their applications still need to be further explored.Compared to other physical and chemical technologies,high pressure technique can not only significantly affect the electronic structures of materials without changing the chemical composition,but also improve their optical properties.With the rapid development of high-pressure technology,especially the continuous development of diamond anvil cell(DAC)equipment,the research on high pressure field has been widely carried out.Studies of materials under high pressures have yielded encouraging results,including bandgap optimization,enhanced structural stability,metallization and piezochromism.Because of their excellent properties,these materials have broad application prospects in different research fields such as multi-functional semiconductor devices mechanical sensors,optoelectronic devices and data storage systems.In the past few years,high pressure,as a kind of environmental protection and efficient tool,have been used in researches of the CDs.We designed and studied the piezochromism behavior of CDs with the help of the high-pressure technology.The controllable piezochromism behaviors of the CDs with the supramolecular interaction-regulated fluorescence mechanism were achieved by surface structure regulation.The ?–? stacking of the ?-conjugated system was enhanced as the pressure increased,which caused a red-shift.In contrast,the hydroxyl-related hydrogen bond eventually caused a blue-shift.Therefore,the luminescent CDs with a blue-shift or red-shift in the PL spectra under high pressure can be acquired by changing the relative amounts of hydrogen bonds and the ?-conjugated system.This study strongly indicates that the regulation of the supramolecular interaction under high pressure is a promising way for the nanomaterials to achieve controllable PL properties.At the same time,we explored and summarized the application of high pressure in CDs research and the relationship between chemical structure and optical properties of CDs in recent years.In summary,high pressure can not only be used to study the relevant mechanism of PL,but also to explore the adjustment of PL.The use of high pressure technology can successfully improve and explore the various performance of CDs and promote the wide application of CDs.