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传感器作为智慧农业高效快速检测的核心器件,广泛应用于现代农业的众多领域。其中,基于电化学方法的传感检测技术因其高选择性、高灵敏度、快速响应且操作简单等优势备受关注[1]。该技术的核心组件是电极材料,通常用作信号识别、转换和传导的关键传感器元件。然而,传统的传感器电极材料存在价格高昂、选择性不强和响应性弱等缺陷,制约了该技术的推广应用。为了满足传感器高灵敏度和高选择性的要求,亟需开发敏感、高效且低成本的传感器电极材料。与石墨烯、碳纳米管、贵金属和导电聚合物等传统电极材料相比,生物炭材料不仅具有原材料来源广泛、成本低廉、制备工艺简单、环境友好和可持续等优势[2],还具有丰富的表面含氧官能团、良好的导电性和孔道修饰能力等特性,被广泛认为是一种极具应用潜力的传感器电极材料。
热解是最常用的生物炭制备技术,然而由生物质直接热解所得的生物炭往往存在比表面积不大和亲和性活性位点不足等缺陷,导致生物炭对重金属离子的富集能力有限,进而难以满足电化学传感器高灵敏度的实际需求[3]。为了改善这些问题,化学活化和杂原子掺杂改性被广泛应用于提高生物炭的孔隙结构和表面活性位点[4]。磷酸 (H3PO4) 、氢氧化钾 (KOH) 、氯化锌 (ZnCl2) 等作为常用的活化剂,不仅能调控孔径分布还能增大比表面积。其中,H3PO4具有丰富的活性官能团、可控性强、副反应少、对设备腐蚀性低、价格低等优势,在生物炭改性中得到广泛报道[5]。如ADHIKARI等[6]研究表明,H3PO4活化制备的纳米多孔炭比表面积和孔容分别高达1 288 m2·g−1和 1.64 cm3·g−1,并对氨表现出优异的传感检测性能。杂原子磷 (P) 的掺杂能有效丰富生物炭的孔隙结构 [7]。以H3PO4为化学活化剂调控孔结构的同时引入P基团,改善生物炭芳环结构的电子分布和表面亲和性。潘静等[8]发现,经H3PO4改性后的生物炭成功引入了含P官能团,增强了对铅离子 (Pb2+) 的吸附能力。然而,目前关于H3PO4高温炭化后生成的含P基团对Pb2+的传感检测性能影响尚不明确。另一方面,H3PO4预处理技术的选择和优化对于提高热解生物炭富集、催化以及电化学性能具有显著影响。在炭化过程中,H3PO4在生物质中的均匀分布是分级孔隙结构和高密度含P官能结构构建的关键步骤。超声空化技术是一种有效的预处理方法,通过引入气泡和涡流,能够实现高效混合、均匀浸渍,并提高反应速率。基于以上分析,可以提出如下猜想:超声空化技术辅助磷酸浸渍一步炭化技术可以实现高活性含磷官能团和多级孔隙在生物质炭中的有效生成和均匀分布,进而大幅提高生物炭对痕量重金属Pb2+的电化学传感检测性能。
为此,本研究以棉秆为原料,H3PO4为浸渍剂通过超声空化辅助H3PO4活化一步炭化制备生物质炭铅检测传感材料,探究了不同炭化温度下含P官能团对铅的检测性能和机制。通过对生物质炭传感检测材料的结构表征和传感检测性能评估,将深入探讨炭化温度对超声空化辅助H3PO4浸渍法生物炭的结构特征、比表面积、孔隙度、含P官能团结构的影响,并进一步研究其对铅传感检测性能的影响因素和机制。这将有助于深入理解超声空化辅助H3PO4浸渍一步炭化制备材料的优化策略,并为高活性铅检测传感材料的设计和应用提供数据支持。通过本研究的开展,为生物质炭的功能改性和电化学传感检测领域的研究提供新的思路和方法。
超声空化辅助磷酸浸渍一步炭化制备高活性铅检测传感器
Preparation of highly active lead detection sensor through ultrasound-assisted phosphoric acid impregnation and one-step carbonization
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摘要: 开发高活性且低成本的生物质炭电极是构建高性能铅检测传感器的关键。以棉秆生物质为原料,通过超声空化辅助磷酸浸渍一步炭化法制备了系列不同温度 (700、750、800、850 ℃) 的磷改性棉秆炭,并基于这些炭材料构建了铅检测传感器。采用N2吸脱附、傅里叶红外光谱、X射线光电子能谱、循环伏安、电化学阻抗谱和阳极溶出差分脉冲伏安法等现代表征及测试技术,探究了不同温度棉秆炭电极孔径分布、化学结构、高活性磷官能团与电化学传感性能间的构效关系。结果表明,800 ℃制备的棉秆炭 (CS800) 具有更高的比表面积 (1 338.57 m2·g−1) 和优异的微/中孔分级结构以及更丰富的C3-P-O基团。这些独特优势的结合使CS800电极具有更高的电化学活性、最低的电子转移电阻 (Rct) 和更强的Pb2+富集能力。在1~100和100~1 000 μg·L−1 Pb2+浓度下,CS800检测峰电流与Pb2+浓度呈现良好的线性关系,线性相关系数R2均高达0.97,检测限灵敏度低至1.38 μg·L−1,并表现出优异的重复性、重现性、稳定性及抗干扰性,表明所制备的棉秆炭电极对Pb2+检测具有巨大的应用潜力。本研究结果可为该类生物质炭电极的制备及性能优化提供参考,也可为重金属监测及分析提供技术支持。Abstract: The development of biochar electrodes with high activity and low cost is essential for the construction of high-performance lead detection sensors. A series of phosphorus-modified cotton stalk carbons at different temperatures (700, 750, 800, 850 ℃) were prepared through ultrasonic cavitation-assisted phosphoric acid impregnation and one-step carbonization method using cotton stalk biomass as raw material, and a lead detection sensor was constructed based on these carbon materials. Using N2 absorption-desorption, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy and anode stripping differential pulse voltammetry and other modern characterization and testing techniques, the structure-activity relationship between pore size distribution, chemical structure, high active phosphorus functional groups and electrochemical sensing properties of cotton stalk carbon electrodes at different temperatures was investigated. The results showed that cotton stalk carbon (CS800) prepared at 800℃possessed higher specific surface area (1 338.57 m2·g−1), more abundant micropore/mesopore structure as well as C3-P-O groups. The combination of these unique advantages gived the CS800 electrode a higher electrochemical activity, the lowest electron transfer resistance (Rct), and a stronger Pb2+accommodation capability. At Pb2+concentrations of 1~100 μg·L−1 and 100~1 000 μg·L−1, the peak current of CS800 appeared a good linear relationship with Pb2+concentration. The linear correlation coefficients R2 were all up to 0.97, and the detection limit sensitivity was as low as 1.38 μg·L−1. Furthermore, excellent repeatability, reproducibility, consistency and anti-interference performance were shown, which indicated that the prepared cotton stalk carbon electrode had great application potential for Pb2+detection. The results of this research not only shed light on the preparation and performance optimization of biochar electrodes, but also offer technical support for the monitoring and analysis of heavy metals.
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表 1 棉秆炭材料的孔径特征
Table 1. Pore size characteristics of cotton stalk carbon materials
炭材料 比表面积/
(m2·g−1)总孔体积/ (mL·g−1) 中孔体积/
(mL·g−1)微孔体积/ (mL·g−1) 微孔占总孔体积/
%平均孔径/
nmCS700 1 153.74 1.25 1.22 0.42 33.60 4.32 CS750 1 238.36 1.02 0.97 0.45 44.10 3.31 CS800 1 338.57 0.95 0.88 0.49 51.60 2.85 CS850 909.09 0.75 0.71 0.33 44.00 3.30 表 2 CS700、CS750、CS800和CS850的表面原子比例
Table 2. Surface atomic ratio of CS700, CS750, CS800 and CS850
% 表面原子 CS700 CS750 CS800 CS850 P2p C1s 70.14 65.28 83.01 72.00 O1s 23.31 27.32 13.39 22.41 P2p 6.55 7.40 3.60 5.59 C-O-P 63.31 59.92 46.10 54.91 C-P-O 29.72 28.63 24.90 24.23 C3-P-O 6.97 11.45 29.00 20.86 -
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