CAJ | 학술논문

采用共沉淀法合成Fe3 O4纳米颗粒，再以柠檬酸三钠还原AgNO3获得了具有SERS活性的Fe3 O4@Ag磁性纳米复合材料。基于密度泛函理论（ DFT）的量子化学计算方法和表面增强拉曼光谱（ SERS）技术，从理论计算和实验测定表征探讨了2-噻吩甲酸（2-TCA）在Fe3 O4@Ag表面的吸附行为和增强效应。结果表明：理论计算得到的拉曼光谱与实际测得的常规拉曼光谱基本一致，而在DFT理论计算中所键连的Ag原子数越多，与实测值就越接近。溶液的浓度和pH对拉曼增强效果有很大的影响，当溶液的pH=3且浓度为1×10-4 mol·L-1时有最大拉曼增强效应。峰强随2-TCA浓度的增加呈现先增大后减小的趋势，浓度过大会导致大量2-TCA分子吸附聚集在Ag表面形成局部“拥堵”，阻碍了激发光尤其是光谱信号的散射通过，从而减弱了拉曼增强效应。 pH的变化使溶液中2-TCA分子形态发生改变，结构形态不同，其在Ag表面的吸附方式也不同。中性C4 H3 SCOOH分子以环上S：形式垂直吸附键合在Ag表面，形成S—Ag配位键而产生SERS光谱。-1价C4 H3 SCOO-离子以S—Ag配位和O—Ag共价“双键合”侧卧方式共同吸附在Ag表面而产生SERS光谱。在Ag表面，以单独S—Ag配位键吸附或键合的能力比S—Ag配位和O—Ag共价共同吸附方式要弱，但其产生的SERS信号更强，故2-TCA中性分子比2-TCA-离子更有利于SERS的产生。随着pH值的增加，溶液中的2-TCA由中性分子逐渐转化为-1价的C4 H3 SCOO-离子，因而在pH>3以后，拉曼增强效应逐步减弱。
채용공침정법합성Fe3 O4납미과립，재이저몽산삼납환원AgNO3획득료구유SERS활성적Fe3 O4@Ag자성납미복합재료。기우밀도범함이론（ DFT）적양자화학계산방법화표면증강랍만광보（ SERS）기술，종이론계산화실험측정표정탐토료2-새분갑산（2-TCA）재Fe3 O4@Ag표면적흡부행위화증강효응。결과표명：이론계산득도적랍만광보여실제측득적상규랍만광보기본일치，이재DFT이론계산중소건련적Ag원자수월다，여실측치취월접근。용액적농도화pH대랍만증강효과유흔대적영향，당용액적pH=3차농도위1×10-4 mol·L-1시유최대랍만증강효응。봉강수2-TCA농도적증가정현선증대후감소적추세，농도과대회도치대량2-TCA분자흡부취집재Ag표면형성국부“옹도”，조애료격발광우기시광보신호적산사통과，종이감약료랍만증강효응。 pH적변화사용액중2-TCA분자형태발생개변，결구형태불동，기재Ag표면적흡부방식야불동。중성C4 H3 SCOOH분자이배상S：형식수직흡부건합재Ag표면，형성S—Ag배위건이산생SERS광보。-1개C4 H3 SCOO-리자이S—Ag배위화O—Ag공개“쌍건합”측와방식공동흡부재Ag표면이산생SERS광보。재Ag표면，이단독S—Ag배위건흡부혹건합적능력비S—Ag배위화O—Ag공개공동흡부방식요약，단기산생적SERS신호경강，고2-TCA중성분자비2-TCA-리자경유리우SERS적산생。수착pH치적증가，용액중적2-TCA유중성분자축점전화위-1개적C4 H3 SCOO-리자，인이재pH>3이후，랍만증강효응축보감약。
Fe3 O4 magnetic nanoparticles were firstly synthesized by co-precipitation method, and Fe3 O4@Ag magnetic material which has improved SERS effect was further prepared by reduction of AgNO3 using sodium citrate. Both density functional theory ( DFT) and surface-enhanced Raman scattering ( SERS) spectroscopy technique were used to investigate the adsorption behavior and en-hancement effect of 2-thiophene carboxylic acid (2-TCA) on the Fe3O4@Ag surface. The results show that Raman spectra of the theoretical calculation and the determination are basically identical, and the more Ag atoms are introduced in theoretical calculation, the closer the measured value is to the theoretical value. The concentration and pH of the solution have great influence on the Raman enhancement effect, and the solution of 1 × 10 -4 mol·L-1 at pH=3 can present excellent Raman signal response. The SERS effect increases initially and decreases afterwards with the increasing of concentration, which can be inferred that a lot of 2-TCA molecules are adsorbed and gathered on the Ag surface to form a local “congestion” and interfere the transmission of the excitation light, espe-cially spectroscopic signal scattering. 2-TCA molecule morphology is changed with the increasing of pH, and the adsorption mode is influenced by the molecule morphology. The neutral C4 H3 SCOOH is vertically adsorbed on the Ag surface by the formation of S—Ag coordination bond. However, C4 H3 SCOO- anion is adsorbed on Ag surface with S—Ag coordinate bond and O—Ag covalent bond which is named as“double-bonged” side pattern. Although the adsorption of S—Ag coordinate bond is weaker than “double-bonged” side pattern, the SERS signal is stronger, because the neutral 2-TCA molecules are more beneficial to the generation of SERS signal comparing with 2-TCA- anion. The neutral 2-TCA molecules are gradually transformed into C4 H3 SCOO- anion with the increasing of pH, which leads to the decreasing of SERS effect gradually after pH>3.