Ghosh Harekrishna, Bouhekka Ahmed, Bürgi Thomas
Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
Département de Physique, Faculté des Sciences Exactes et Informatique, Université Hassiba Ben Bouali, 02000 Ouled Fares-Chlef, Algeria.
Phys Chem Chem Phys. 2016 Sep 29;18(38):26942-26948. doi: 10.1039/c6cp05098k.
Germanium-polyelectrolyte-gold nanoparticle composites were prepared and characterized using FTIR-ATR spectroscopy and scanning electron microscopy. The germanium (Ge) element served as an internal reflection element and the buildup of the layered system was followed in situ. A positively charged polyelectrolyte, poly (allylamine hydrochloride) (PAH) adsorbs spontaneously on negatively charged Ge. Citrate-stabilized gold nanoparticles can then be adsorbed onto the PAH layer. Upon illumination of the device with visible light a prominent absorption over the entire mid infrared region is observed which is due to intervalence band transitions in Ge. The strong infrared signals are evidence for holes in the valence band of the Ge semiconductor, which arise due to electron transfer to the gold nanoparticles (GNPs). The electron transfer, as evidenced by the holes in Ge, is affected by the nature of the gap between the Ge semiconductor and the GNPs. Increasing the gap by adsorbing polyelectrolyte multilayers hinders the electron transfer. Also, heating and vacuum have a pronounced effect. The device is proposed as a sensor, where the sensing event is transduced into an optical signal in the infrared region, as demonstrated for a thiol molecule. The thiol has a large affinity for gold, and therefore affects the germanium-gold nanoparticle gap. This reduces the electron transfer, and therefore the absorption in the infrared region upon illumination with visible light. Removal of the thiol from the solution leads to the recovery of the signal.
制备了锗-聚电解质-金纳米颗粒复合材料，并使用傅里叶变换红外衰减全反射光谱（FTIR-ATR）和扫描电子显微镜对其进行了表征。锗（Ge）元素用作内反射元件，并对层状体系的形成进行原位跟踪。带正电荷的聚电解质聚（烯丙胺盐酸盐）（PAH）会自发吸附在带负电荷的Ge上。然后，柠檬酸盐稳定的金纳米颗粒可以吸附到PAH层上。用可见光照射该器件时，在整个中红外区域观察到明显的吸收，这是由于Ge中的价带间跃迁所致。强烈的红外信号证明了Ge半导体价带中的空穴，这些空穴是由于电子转移到金纳米颗粒（GNP）而产生的。如Ge中的空穴所证明的，电子转移受Ge半导体与GNP之间间隙性质的影响。通过吸附聚电解质多层膜来增加间隙会阻碍电子转移。此外，加热和真空也有显著影响。该器件被提议用作传感器，其中传感事件被转换为红外区域的光信号，如对硫醇分子的演示。硫醇对金具有很大的亲和力，因此会影响锗-金纳米颗粒间隙。这会减少电子转移，从而减少可见光照射时在红外区域的吸收。从溶液中去除硫醇会导致信号恢复。
