Activating Room Temperature Phosphorescence Of Carbon Dots Based On The Intercalation Effect And Its Applications

Organic phosphorescence materials have aroused particular attention in optoelectronic applications involving photovoltaics,photocatalytic reactions and sensing.To improve the phosphorescence effeciency,noble metals(Pt,Au,etc)are usually employed,which is high-cost and toxic.While some non-noble metal materials have been used to inhibit radiationless relaxation,harsh conditions associated with carefully selected hosts,rigid solid-state crystalline structure and low temperature environment are commonly needed.Importantly,these non-noble metals make an insignificant contribution to spin orbit coupling(SOC).Layered double hydroxides(LDHs)are typitical inorganic layer materials which exhibit great versatility in their chemical composition and the ability to form two-dimensional(2D)arrayed structures.In this dissertation,we envisage using LDHs as hosts to activate room temperature phosphorescence(RTP)of carbon dot guest.Subsequently,the luminescence mechanism was systematically studied.Single-layered graphene quantun dots(GQDs)with an exact structure are obtained in the confined nanospace of LDHs.The confined space of the 2D interlayer galleries of LDHs is beneficial for the formation of luminescent groups in GQDs and enhancing the luminescence efficiency.The composite can be potentially applied in anti-counterfeiting field and temperature-response phosphorescence sensor.The main contents of the dissertation are as follows:LDHs as nano-generators provide a confined microenvironment for the construction carbon dots/LDHs composite by in-situ synthesis.The RTP of CDs was activated by employing an inorganic LDH matrix with orderly non-noble metal arrays and dual structural confinements.The non-noble metals on the LDH layer substitute noble metals to strengthen the SOC of singlet-triplet excitons.The confinement effects of the LDH layer and interlayer simultaneously restrict the motions of CDs in the LDH interlayer,and effectively suppress the radiationless relaxation pathways and enhance the RTP.LDHs provide a confined microenvironment for the formation of GQDs,inhibiting the growth of GQDs along the Z axis,which is a prerequisite for achieving a single-layered GQD with an exact structure.To investigate the chemical composition and structure of the GQDs in the LDH layer,X-ray photoelectron spectroscopy(XPS),nuclear magnetic resonance(NMR),and electrospray ionization mass spectrometry(ESI-MS)were used to infer the molecular formula.The structure-property relationship is disclosed by combining theoretical and experimental data,demonstrating that the highly efficient dual-emission property of the GQDs-LDHs originates from the synergistic effects involving structural confinements owing to LDHs and the rich O-containing functional groups resulting from LDH catalysis.Moreover,the colorless nature and dual-emission characteristics of GQDs-LDHs satisfy the preconditions as anti-counterfeiting markers for protecting valuable documents(bank notes,commercial invoices,etc.).Particularly,owing to the low toxicity of GQDs and the edible property of LDHs,the GQDs-LDHs/gelatin capsules could be the new generation of potential green anti-counterfeiting material in the field of food and drugs.