講座主題：Carrier separation and exciton structure in graphene quantum dots and carbon nitride quantum dots
專(zhuān)家姓名：張瑞勤
工作單位：香港城市大學(xué)
講座時(shí)間：2023年12月15日 10:00-11:00
講座地點(diǎn)：騰訊會(huì)議：988-447-622
主辦單位：煙臺(tái)大學(xué)物理與電子信息學(xué)院
內(nèi)容摘要：
Graphene quantum dots (GQDs) and Carbon nitride quantum dots (CNQDs), the latest addition to the carbon material family promise numerous novel applications in optical sensing, photo-catalysis, bio-sensing, and photovoltaics. However, understanding the photocatalytic capability of CNQDs compared to the graphene quantum dots (GQDs) have not been investigated thoroughly. In this work, through time-dependent density functional tight binding (TD-DFTB) calculations, it is revealed that due to the ground state frontier molecular orbitals (FMOs) localization, CNQDs have superior carrier charge separation, sensitive to the size of the QD. Strong localization of the FMOs and excited state charge separation was observed in the first excited state due to the relaxation of the structure. The exciton structure reveals spatial confinement to the stretched C-N bonds independent of the size of the QDs while there is no such exciton structure found for GQDs. The optical absorption and emission of CNQDs is sensitive to size and does not show strong variations in the shape of the QD. Our approach provides an explanation for the origin of the enhanced photocatalytic performance of CNQDs over graphene quantum dots (GQDs) and their characteristic exciton localization.
主講人介紹：
張瑞勤,，香港城市大學(xué)物理與材料系教授,，獲德國(guó)洪堡基金會(huì)貝塞爾研究獎(jiǎng)（2004 年）、兩項(xiàng)國(guó)家自然科學(xué)獎(jiǎng)（1997和2005年）和一項(xiàng)教育部獎(jiǎng)項(xiàng)（1997年）,，為Journal of Electronic Materials副編輯和AAPPS Bulletin高級(jí)編輯,，歷任香港物理學(xué)會(huì)主席（2013-2017年）和亞太物理學(xué)會(huì)(AAPPS)理事（2016年至今），2018年被選為美國(guó)物理學(xué)會(huì)會(huì)士(APS Fellow),，2020年起為斯坦福前2%高被引科學(xué)家,。
張教授將計(jì)算物理和實(shí)驗(yàn)手段相結(jié)合對(duì)多學(xué)科交叉領(lǐng)域的諸多關(guān)鍵科學(xué)和技術(shù)問(wèn)題進(jìn)行了研究，在發(fā)展多體理論和多電子大體系有效計(jì)算方法的基礎(chǔ)上,，系統(tǒng)研究了限域量子態(tài)（包括電子,、激子和聲子）的行為對(duì)環(huán)境、應(yīng)力,、壓力和光的響應(yīng)和性質(zhì)的調(diào)控,，特別是認(rèn)識(shí)到低維體系顯著的表面-體積比對(duì)量子態(tài)性質(zhì)調(diào)控的有效性，成功系統(tǒng)地揭示了低維體系的一系列由表面和應(yīng)力決定的新穎性質(zhì),，證明了低維體系的表面和應(yīng)力效應(yīng)同量子限域效應(yīng)同等重要,。
