【作者】 刘念；

【导师】 冯波；

【作者基本信息】 湘潭大学 ， 环境工程， 2024， 硕士

【摘要】 六价铬离子(Cr(Ⅵ))因其高毒性和对生物体及环境的严重威胁,已成为全球范围内关注的重点污染物。因此,开发有效的检测和治理技术显得尤为重要。传统的光谱学、电化学分析法及物理化学法在Cr(Ⅵ)检测与去除上受限于检测范围、操作复杂性和样本前处理等问题。然而随着碳纳米技术的飞速发展,其在Cr(Ⅵ)检测与去除领域展现了巨大的潜力和优势。碳纳米材料,特别是碳点(Carbon dots,CDs),因其优异的荧光性能,能够产生强烈的荧光信号,进而开发出高灵敏度的比例型荧光探针,用于低浓度Cr(Ⅵ)的精准检测。此外,碳纳米材料还具备优良的光学性质,可以有效吸收可见光和紫外光,并将其转化为化学能,从而驱动光催化还原反应。其高表面积和孔道结构为光催化反应提供了充足的界面,显著提升了反应效率。本研究基于碳纳米材料在Cr(Ⅵ)污染控制中的潜力,采用水热法成功合成了具有单发射双激发特性的荧光CDs,并将其作为比例型荧光探针,用于水体中Cr(Ⅵ)的精准检测。进而,通过CDs改性二氧化钛纳米棒(Titanium dioxide nanorods,TNR),制备了CDs-TNR光催化材料,并对其在Cr(Ⅵ)还原中的应用进行了系统研究。主要研究内容如下:(1)本研究优化了CDs、TNR以及CDs-TNR的合成条件,确保了材料的优良性能。通过SEM、TEM、XRD、BET、TGA、FT-IR以及UV-Vis DRS等多种表征手段,深入探究了材料的物理化学特性。结果显示,CDs成功负载在TNR表面,且CDs的掺杂并未改变TNR的晶体结构。(2)合成的CDs展现出单发射双激发的蓝色荧光特性,并作为比例型荧光探针用于Cr(Ⅵ)的定量检测。研究揭示了荧光猝灭的机制,即CDs与Cr(Ⅵ)之间的内滤效应和静态猝灭作用。CDs具有良好的水溶性和较强的光稳定性,与Cr(Ⅵ)在5μM～100μM浓度范围内呈良好的线性关系,检测限为0.589μM。回收率在92.45%～106.49%之间,展现出良好的准确性和实用性。(3)我们进一步探讨了CDs-TNR光催化还原Cr(Ⅵ)的影响因素、光电性质及还原机理。实验结果表明,CDs-TNR具有较高的Cr(Ⅵ)还原率和出色的循环稳定性,且其还原效率受p H值影响。通过一系列表征手段,本研究揭示了CDsTNR的光响应能力和光生电子-空穴分离效率,并深入解析了催化剂的能带结构和催化机理。此外,自由基清除实验和ESR测试进一步证实了体系中光还原反应的主要活性成分。更多还原

【Abstract】 Hexavalent chromium ion(Cr(Ⅵ))has become a focus pollutant worldwide because of its high toxicity and serious threat to organisms and environment.Therefore,the development of effective detection and treatment technology is particularly important.The traditional spectroscopy,electrochemical analysis and physicochemical methods in Cr(Ⅵ)detection and removal are limited by the detection range,operational complexity and sample pretreatment.However,with the rapid development of carbon nanotechnology,it has shown great potential and advantages in the field of Cr(Ⅵ)detection and removal.Carbon nanomaterials,especially Carbon dots(CDs),can generate strong fluorescence signals due to their excellent fluorescence properties,and then develop high-sensitivity proportional fluorescence probes for the accurate detection of low concentration Cr(Ⅵ).In addition,carbon nanomaterials also have excellent optical properties,which can effectively absorb visible and ultraviolet light and convert it into chemical energy,thereby driving photocatalytic reduction reactions.Its high surface area and pore structure provide sufficient interface for photocatalytic reactions,significantly improving the reaction efficiency.In this study,based on the potential of carbon nanomaterials in Cr(Ⅵ)pollution control,fluorescent CDs with single emission and double excitation characteristics were successfully synthesized by hydrothermal method,and they were used as proportional fluorescent probes for accurate detection of Cr(Ⅵ)in water.Further,CDS-TNR photocatalytic materials were prepared by modifying Titanium dioxide nanorods(TNR)with CDs,and their application in Cr(Ⅵ)reduction was systematically studied.The main research contents are as follows:(1)Firstly,the synthesis conditions of CDs,TNR and CDS-TNR were optimized to ensure the excellent properties of the materials.The physicochemical properties of the materials were investigated by SEM,TEM,XRD,BET,TGA,FT-IR and UV-Vis DRS.The results show that CDs is successfully loaded on the TNR surface,and the doping of CDs does not change the crystal structure of TNR.(2)The synthesized CDs exhibited the blue fluorescence characteristics of single emission and double excitation,and were used as a proportional fluorescence probe for the quantitative detection of Cr(Ⅵ).The mechanism of fluorescence quenching was revealed,that is,the internal rate effect and the static quenching between CDs and Cr(Ⅵ).CDs has good water solubility and strong light stability,and has a good linear relationship with Cr(Ⅵ)in the concentration range of 5 μM ～ 100 μM,and the detection limit is 0.589 μM.The recovery rate is between 92.45% and 106.49%,showing good accuracy and practicability.(3)The influence factors,photoelectric properties and reduction mechanism of CDs-TNR photocatalytic reduction of Cr(Ⅵ)were further discussed.The experimental results show that CDs-TNR has high Cr(Ⅵ)reduction rate and excellent cycling stability,and its reduction efficiency is affected by p H value.Through a series of characterization methods,this study revealed the photoresponse and photogenerated electron-hole separation efficiency of CDs-TNR,and analyzed the band structure and catalytic mechanism of the catalyst.In addition,free radical scavenging experiments and ESR tests further confirmed the main active components of photoreduction reaction in the system.更多还原