Study On Electrochemical Luminescence Properties Of Graphene Facilitated And Gold Nanocluster Aggregation Induction

Electrochemiluminescence（ECL）is the chemiluminescence produced by electrochemical reaction.The high sensitive ECL analytical technique has been applied successfully in environmental and biological detections.ECL luminophore is the cornerstone of ECL analytical method.The development of ECL luminophore with better performance is an important ECL research.In recent years,nanomaterials as the ECL luminophores has attracted much attention.In this thesis,reduced graphene（GR）has been grown on glassy carbon electrode（GCE）by a simple and efficient electrochemical method,and its luminescence mechanism has been studied by ECL spectrum.In addition,a new type of aggregation-induced emission rigid alloy nanocluster,Au Ag CBz NCs,was designed and synthesized,which has excellent anodic ECL performance and is used for sensitive detection of dopamine（DA）.The main research contents are outlined below.1.A simple ECL spectrum measurement device to investigate the mechanism of reduced graphene enhanced cathodic ECLThe time-dependent of ECL intensity makes it difficult to measure the ECL spectrum by a spectrometer with a photomultiplier tube（PMT）as the detector in wavelength scan mode.Althrough the spectrometer using CCD camera as detector can simultaneously measure the spectrum from ultraviolet to near-infrared region without the influence of the time-dependent intensity,the sensitivity of CCD is much lower than that of PMT.As a reslt,the CCD based ECL spectrometer is not suitable to measure the spectrum of weak ECL systems.In this work,a home-made band-pass filter turnable is mounted in a conventional ECL analyzer to enhance the sisitivity for the ECL spectrum measurement.The influence of the variation of ECL intensity over time on the ECL spectral measurement is corrected by the data analysis program.The spectrum of the cathodic ECL of bare GCE in K₂S₂O₈solution is measured,indicating that the device can be used for the spectrum measurement of extremely weak ECL systems.Graphene has excellent electrocatalytic activity and conductivity,and is often used as an electrode modification material to improve the sensitivity of electrochemical sensors.Interestingly,when bare GCE was immersed in aqueous electrolyte solution（such as 1M Na₂SO₄）and a certain negative voltage was applied,a carbon nanomaterial film,possiblely being GR reduced from GCE,was obtained on the surface of GCE.In the presence of K₂S₂O₈as cathodic coreactant,the resulting GCE/GR exhibited strong and stable cathodic ECL signal with the intensity 73 times of the ECL intensity in the bare GCE-K₂S₂O₈system.Importantly,the shape of ECL spectrum of GCE/GR and bare GCE in K₂S₂O₈solution is near the same.Hence,it is reasonable to consider that the cathodic ECL of GCE/GR in K₂S₂O₈solutionis ascrbled to the cathodic ECL of O₂/S₂O₈^2-promoted by GR,indicating that ECL spectrum can provide valuable information for the ECL mechanism.The cathodic ECL of GCE/GR is used to detection of Cu²⁺in the concentration range from 1 n M to 10μM,with the detection limit of 0.3 n M.2.Enhancement aggregation induced ECL of gold nanoclusters via rigidity strengthening for dopamine determinationGold nanoclusters（AuNCs）have excellent luminescence properties and good biocompatibility,have a promising application prospect in the field of cell imaging and sensors.In this work,two strategies were used to enhance the luminescence efficiency of Au NCs.Fristly,Ag NO₃was doped into HAu Cl₄and mercaptan ligand glutathione（GSH）to form Ag（0）and Ag（I）-GSH mercaptan complexes.The number of M（0）and M（I）-GSH mods was increased to enhance luminescence.Secondly,a layer of rigid structure molecule Benzyl chloroformate（CBz）was attached outside the alloy nanocluster（MNNCs）by the action of amide.The strengthening rigidity of MNNCs limits the intramolecular motion and reduces the energy loss due to non-radiative relaxation,thus enhancing luminescence.The fluorescence signal was enhanced 3.8times by a two-step enhancement strategy.GCE/Au Ag CBz NCs can generate annihilation-type ECL signals during hole injection.When Au Ag CBz NCs was deposited on the surface of GCE,a high aggregation state was obtained.In the presence of tripropylamine（TPr A）as the anodic coreactant,TPr A was oxidized before Au Ag CBz NCs during the anodic potential scan process.Then Au Ag CBz NCs are oxidized by the oxidation products of TPr A and emits AIECL.Under the condition used,the AIECL intensity is 120-folds of that of Au NCs.The AIECL of Au Ag CBz NCs was used to construct an ECL sensor for dopamine detection.The linear concentration range of the proposed ECL sensor was 5 nM～5μM with the detection limit of 1.9 nM.