单分子电子器件具有一系列与经典电子元件类似的特性，包括开关、传感器、整流器和晶体管等。这种分子器件在小型化、功耗、稳定性和运行速度方面对提升现有集成电路的集成密度具有很大的潜力。对相关器件的输运特征和散粒噪声研究是目前该领域的前沿热点问题。在本论文中，我们采用非平衡态格林函数处理方法并结合拓展的休克尔（Hückel）理论，研究了几种分子和纳米结构电子器件的态密度、传输系数和电压电流曲线等输运特性。此外，我们还计算了部分器件的法诺（Fano）因子，通过散粒噪声提供的额外电子关联信息研究了输运现象。论文的主要成果如下：1) 对于联苯二硫酚和联苯二胺分子器件，当电极和被固定基团从全耦合到弱耦合的变化时，我们在计算中观察到偏压及锚定基团对输运特性变化的影响。并且，我们还在这类器件中发现散粒噪声的规则与不规则变化由于受到泡利不相容原理的抑制而偏离经典泊松期待值的现象。这些研究加深了对这些器件行为的理解。2) 对于以石墨烯为基底的电子器件和传感器。我们通过用诸如氮或硼的外部原子来取代石墨烯上的碳原子与气体吸收来改进导电性。藉此，我们研究了NC3H 量子点器件在吸附氨分子或者二氧化碳分子后的输运特性，给出了吸附上述分子后的电子器件电压电流特性，以及吸附氨分子不同配置所带来的输运特性变化，为量子点气体探测器等纳米级电子器件的制备提供了理论探索。3) 对于4,4'-（乙烷-1,2-二取代）联二硫基苯器件，以及其以非共价吸附的形式吸附在石墨烯表面后的器件输运特性。我们发现吸附在石墨烯表面的器件输运特性有显著的改变，导电能力得到增强，并且具备了开关的特性。

Single molecule electronic devices have similar properties to traditional electronic components, such as switches, sensors, rectifier and transistor, etc. In term of device miniaturization, power consumption, stability and performance, these molecular devices have great potential to increase the integration density due to drastic decreases in the size of device. Transport properties and shot noise of the devices are one of the most focused subjects. In this thesis, we use the Non-equilibrium Green’s Function (NEGF) formalism in combination with the Exended Hückel Theory (EHT) to calculate the transport properties such as the density of states (DOS), transmission functions (TE), and current-voltage (I-V) characteristics of several molecular devices. In addition, we use shot noise as a powerful tool to investigate transport phenomena, since it provides additional information about electron correlations from the calculated Fano factor. Major achievements of this thesis are: 1) For Biphenyl dithiol (BPDT) and Biphenyl diamine (BPDA) molecule devices. The changes of transport properties are observed with the effect of applied bias and the anchoring group as coupling between electrode and anchoring group changes from full to weak coupling. Shot noise in these devices deviates from the classical Poissonian expected value due to Pauli principle, resulting suppression of shot noise. The regular and irregular changes of shot noise observe in (BPDA) and (BPDT) devices, respectively that provide better understanding about the behaviour of these devices.2) Substitution of carbon due to external atom like Nitrogen or Boron and adsorption of gases on graphene surface modifies the graphene based electronic devices. Herein, we study the transport properties of NC3H quantum dot devices by adsorption of ammonia and carbon dioxide. Our results demonstrate that the changes in the transport properties with the adsorption of ammonia molecule in different configurations are useful for making nano scale electronic devices, such as quantum dot gas sensor.3) For the 4,4'-(ethane-1,2-diyl) dibenzenethiol (EDBT) molecular device and 4,4'- (ethane-1,2-diyl) dibenzenethiol adsorb on graphene surface via a non-covalent way, we find that the adsorption of (EDBT) molecular system on graphene surface can significantly alter the transport properties and increase the conducting capability through the device and the device showing the switch characteristic