摘要
纤维素是存在于植物细胞壁中的天然高分子化合物,因其独特的生物相容性、可再生性和环境友好性而备受瞩目。为提高纤维素的电学性能,基于密度泛函理论,采用第一性原理计算的方法,探讨了氧原子掺杂对纤维素电学特性的调控规律。结果发现:纤维素是带隙为4.938 eV的绝缘体,当纤维素中的碳原子被氧原子替换后,其电学特性发生了显著的变化;其中,O_(2)原子替换C_(1)或C_(3)后体系带隙明显减小,呈半导体特征,替换原子与周围原子之间的相互作用发生改变,电子局域性增强;O_(2)原子替换C_(2)或C_(4)后体系价带向导带偏移,甚至超过费米能级,表现出半金属特征,而O_(2)原子替换C_(5)后体系仍然表现为绝缘体;当O_(2)原子替换碳的位置时,由于氧原子的电负性较强,易与周围的碳原子形成稳定的共价键,从而限制了电子的跃迁,导致体系的带隙明显减小,导电性增强。
Objective Cellulose is a complex macromolecular polysaccharide formed by glucose units connected byβ-1,4-glycosidic bonds.It is a natural polymer compound primarily found in plant cell walls,gaining attention for its unique biocompatibility,renewability,and environmental friendliness.The molecular chains of cellulose can intertwine like ropes,forming various structural morphologies.Cellulose has several allomorphic crystalline forms,which lead to diverse physical properties.Generally,at the molecular level,cellulose has various forms of external defects,including disorder in molecular chain arrangement and the presence of voids,cracks,and impurities in its microstructure.On the one hand,the defects would weaken the mechanical properties of celluloses and severely affect the chemical stability and reactivity.On the other hand,the defects in the cellulose such as impurities change the electrical properties.As one example,the doping of oxygen(O)in the cellulose would transform the polymer from an insulator to a semiconductor.However,the basic mechanisms at the electronic scale of the cellulose are still unclear.Method To deepen the understanding of the changes in electrical characteristics of cellulose after doping,in this work,we investigated the regulation of electrical properties by O doping through the first-principles calculations based on the density functional theory.Calculations were carried out using the Vienna Ab-initio simulation pack-age(VASP).The energy cutoff for the plane wave basis set was set to 450 eV,and the interactions between ionic cores and valence electrons were described using the projector augmented wave(PAW)method.For the exchange-correlation functional,the generalized gradient approximation(GGA)with the Perdew-Burke-Ernzerhof(PBE)functional was employed.During structural relaxation,the force convergence criterion was set to less than 0.01 eV/,and the total energy convergence criterion was set to less than 1.0×10^(-5) eV.Results The results indicate that the perfect cellulose has a band gap of 4.938 eV,showing almost no conductivity and exhibiting insulating properties.The conduction band minimum is located to the left of the high-symmetry point D,while the valence band maximum is situated to the right of point D,indicating an indirect band gap.The energy bands are more curved between 5 eV and 8 eV,while they are relatively flat between 0 eV and-8 eV,showing a higher degree of electron localization.When carbon(C)atoms in cellulose were replaced by oxygen(O)atoms,significant changes occurred in its electrical properties.Secondly,when the O_(2) atom replaced C_(1) or C_(3),the band gap of the system decreased significantly,exhibiting semiconductor characteristics.The interaction was changed accordingly between the replaced atom and surrounding atoms,resulting in enhanced electronic localization.The density of states was relatively flat between 0 eV and-10 eV,with a high degree of electronic localization primarily contributed by the p orbitals of O_(1) and O_(2).Thirdly,when the O_(2) atom replaced C_(2) or C_(4),the valence band of the system shifted toward the conduction band,even surpassing the Fermi level,displaying half-metallic characteristics.Compared to undoped cellulose,the density of states near the Fermi level changed significantly,primarily contributed by the O_(2) atom,but with a smaller effect on the conduction band.When the O_(2) atom replaced C_(5),the system still behaved as an insulator,the band gap of the system increased and the energy bands remain relatively curved between 5 eV and 6 eV,while being flat between 0 eV and-9 eV,with a high degree of electronic localization.Conclusion In summary,the replacement of C atom in cellulose with O atom significantly alters its electronic properties due to the higher electronegativity of O,which tends to form stable covalent bonds with surrounding C atoms,thereby limiting electron transitions.However,different substitution sites exhibit distinct properties.Therefore,when preparing and functionally modifying cellulose,the substitution sites of O atom should be given special consideration.By applying doping effects to cellulose,its electrical properties can be significantly altered,offering new insights for the application of cellulose in the engineering field of electronic devices.
作者
王恩奇
郭萌生
胥茹柳
陈凤祺
樊威
苗亚萍
WANG Enqi;GUO Mengsheng;XU Ruliu;CHEN Fengqi;FAN Wei;MIAO Yaping(College of Textile Science and Engineering,Xi′an Polytechnic University,Xi′an,Shaanxi 710048,China;Key Laboratory of Functional Textile Materials and Products,Ministry of Education,Xi′an,Shaanxi 710048,China)
出处
《纺织学报》
北大核心
2025年第2期43-50,共8页
Journal of Textile Research
基金
国家自然科学基金青年科学基金项目(52202111)
大学生创新创业训练计划创新训练项目(S202310709120)。
关键词
纤维素
第一性原理计算
氧原子掺杂
能带
态密度
电学性能
cellulose
first-principle calculation
O doping
band structure
density of state
electrical property
