Study Of The Preparation Of Orpiment Quantum Dots And Mechanisms

In the field of photoelectronics, orpiment(As2S3) possesses third-order nonlinearoptical properties and memory function, enabling it a research focus in recent years. Inthe field of biomedicine, orpiment achieves potent effect in the treatment of earlypromyelocytic leukemia. Matter with nanometer scale from1to100nm will presentunique properties, different from both microscopic molecules and atoms andmacroscopic matter. In recent years, the researchers prepared orpiment nanoparticalswith the aim to find more unique properties for developing its potential applications. Inthis paper we firstly prepared orpiment nanocrystals by a chemical method. Theorpiment nanocrytals within size smaller and narrower range (e.g.,1-20nm), has acharacteristic quantum confined effects, such as fluorescence emission after lightexcitation, so that they could be called orpiment (fluorescent) quantum dots. In addition,orpiment quantum dots synthesized were found to be not only miscibility with aqueousand many other solutions, but also were long-term stable in these solvent systems interms of flurescent emission. These advantages make orpiment quantum dots applicablein the biomedical fields. For example, compared with commonly used orpiment powerfor treatment of cancerous diseases, the water solubility and bioavailability of quantumdots are close to100%. Compared with commercial water-insoluble CdSe quantum dotsfluorescent biomarker, water soluble orpiment quantum dots could be used directlywithout any further post-treatment for improving water solubility.High quality orpiment quantum dots were prepared by using ethanolamine andtriethanolamine as chelating agent/solvent in this study. We investingated the effects ofreaction temperature, reaction time, concertration of precursors, type and amounts ofacid on the preparation. For ethanolamine-base system, the optimized condition asfollow: precursor concentration of40mg/mL, reaction temperature115℃, citric acid asthe proton reagent and reaction time48h. For ethanolamine and triethanolamine-basesystem, the optimized conditions as follow: ratio of ethanolamine to triethanolamine1:9,precursor concentration of20mg/mL, the reaction temperature115℃, citric acid as theproton reagent and reaction time48~72h.We also prepared orpiment dots containing composites using agar as matrixmaterial. In the preparation, we found that orpiment quantum dots are sensitive to pH.When pH was less than6.0, orpiment quantum dots precipitated out from the system. In this study, we also carried out preliminary study of preparation and characterization ofthe self-assembly of orpiment quantum dots.Based on the results, we proposed the preparation mechanism of orpimentquantum dots: ligands and orpiment react to molecular cluster solution as precursors. Byadjusting acid added, the resulting molecular cluster undertake nucleation and growth toobtain orpiment quantum dots.