Sensing Research Based On Graphene Quantum Dots And Black Phosphorus Quantum Dots

Quantum dots,usually have a size less than 100 nm.Due to their large surface area,high chemical activity and significant quantum confinement effect,quantum dots have drawn wide attention in recent years.Graphene quantum dots(GQDs)have the graphene-like structure and GQDs are rich in functional groups on surface.In addition,GQDs have stable fluorescent without photobleaching and light scintillation.Therefore,GQDs are often used in fluorescence sensors to detect analytes.In black phosphorus quantum dots(BPQDs)structure,each phosphorus has a pairs of electrons which produce high surface activity.At present,there are many reports on the properties of optical,electrochemical,biological and applications of BP nanosheets.The unique high specific surface area,significant quantum confinement effect and luminescent properties of BPQDs still need to be developed.In this work,GQDs and BPQDs were used as sensing elements.GQDs were used to detect Fe3+ ions quantitatively by stable fluorescent properties.Fe3+ could be identified from other interfering ions and the interpretation based on pH-Ksp theory for the selective detection was given reasonable.BPQDs as moisture-sensitive elements were applied as humidity sensor.The sensitivity of BPQDs to moisture could be enhanced by conductive carbon materials.This work mainly includes the following aspects:1.Fuorescent GQDs stripping from carbon black by nitric acid were obtained with size about 10 nm.GQDs are rich of oxygen-containing functional groups on surface,while complex with metal ions forming complexes to induce GQDs aggregation and then quenched fluorescence signal.At different pHs,GQDs have different affinity to different metal ions.Therefore,the detection of Fe3+ has achieved satisfactory selectivity when carried out in a certain pH range.A reasonable explanation of the selectivity principle is given based on Ksp-pH theory.2.Strip two-dimensional flaky BP to obtain BPQDs and make thin-film moisture sensitive elements.During different humidity cycles,the electrical signals generated by BPQDs responded quickly and the response and recovery time was extremely short.But as an excellent moisture-sensitive materials,sensitivity of BPQDs still could be improve.Graphene,graphene oxide and nitrogen-doped carbon dots(N-CDs)formed composites with BPQDs to improve sensitivity.N-doped affected the electronic structure of the carbon dots and enhanced the electron transfer capacity thus the sensitivity was significant improved.3.Copper-based metal organic frameworks(HKUST-1)has unsaturated metal sites and oxygen-containing ligands that can be used for humidity sensing.The ultrathin HKUST-1 nanosheets were synthesized.The ultrathin 2D structure is more conducive to mass transfer meanwhile can be exposes more active sites.Compared with HKUST-1 bulk,the ultrathin HKUST-1 nanosheets are better humidity sensor.In order to improve the humidity sensitivity of MOFs,BPQDs/HKUST-1 composite sensor was prepared.The sensitivity of the composites was improved by one order of magnitude compared with HKUST-1 alone.