Instituto de Física del Litoral (CONICET-UNL), Güemes 3450, Santa Fe, Argentina.
Phys Chem Chem Phys. 2019 Jan 2;21(2):597-606. doi: 10.1039/c8cp05093g.
We modeled a type of field-effect transistor device based on graphene for the recognition of amino acids with a potential application in the building of a protein sequencer. The theoretical model used was a combination of density functional theory (DFT) with the non-equilibrium Green's function (NEGF) in order to describe the coherent transport in molecular devices. First, we studied the physisorption of each amino acid on a graphene sheet and we reported the adsorption energy, the adsorption distances, the equilibrium configuration and the charge transfer of ten amino acids that can be considered as representative of all of the amino acids: histidine (His), alanine (Ala), aspartic acid (Asp), tyrosine (Tyr), arginine (Arg), glutamic acid (Glu), glycine (Gly), phenylalanine (Phe), proline (Pro) and lysine (Lys). As a result, significant differences were found in the density of states (DOS) after adsorption and there was a change in the semi-metallic character of the graphene due to the lysine and arginine interactions. Furthermore, we noticed changes in the electrical characteristics of the devices, as the amino acids adsorbed onto the surface of the graphene. The curves of current vs. bias voltage (I-Vb) display a distinct response for each amino acid, i.e. the I-Vb curves produce a characteristic footprint for each amino acid. We identified a possible rectification mechanism related to the voltage profile asymmetry, where the amino acids can control the transport characteristics in the device, i.e. Lys and Phe amino acids physisorbed on graphene act as a molecular diode, where electrons can easily flow in one direction and decrease in the other. This may be promising for the prospect of biosensors: graphene could be used as an amino acid detector.
我们基于石墨烯构建了一种场效应晶体管器件模型，用于识别氨基酸，该模型在构建蛋白质测序仪方面具有潜在的应用。理论模型是将密度泛函理论（DFT）与非平衡格林函数（NEGF）相结合，以描述分子器件中的相干输运。首先，我们研究了每种氨基酸在石墨烯片上的物理吸附，并报告了十种可以代表所有氨基酸的氨基酸的吸附能、吸附距离、平衡构型和电荷转移：组氨酸（His）、丙氨酸（Ala）、天冬氨酸（Asp）、酪氨酸（Tyr）、精氨酸（Arg）、谷氨酸（Glu）、甘氨酸（Gly）、苯丙氨酸（Phe）、脯氨酸（Pro）和赖氨酸（Lys）。结果发现，吸附后态密度（DOS）有显著差异，由于赖氨酸和精氨酸的相互作用，石墨烯的半金属特性发生了变化。此外，我们注意到，由于氨基酸吸附在石墨烯表面，器件的电特性发生了变化。电流与偏压（I-Vb）的曲线对每种氨基酸都有明显的响应，即 I-Vb 曲线为每种氨基酸产生特征足迹。我们确定了一种可能与电压分布不对称有关的整流机制，其中氨基酸可以控制器件中的传输特性，即吸附在石墨烯上的赖氨酸和苯丙氨酸可以作为分子二极管，电子可以很容易地沿一个方向流动，而沿另一个方向流动则减少。这对于生物传感器的前景可能是有希望的：石墨烯可以用作氨基酸探测器。
