Laboratory for Molecular Photonics, Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL, 33146-0431, USA.
Grup de Materials Orgànics, Departament de Química Inorgànica I Orgànica (Secció de Química Orgànica), Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Martí i Franqués 1, 08028, Barcelona, Spain.
Top Curr Chem (Cham). 2016 Oct;374(5):73. doi: 10.1007/s41061-016-0073-8. Epub 2016 Sep 28.
Photochromic or photocaged ligands can be anchored to the outer shell of semiconductor quantum dots in order to control the photophysical properties of these inorganic nanocrystals with optical stimulations. One of the two interconvertible states of the photoresponsive ligands can be designed to accept either an electron or energy from the excited quantum dots and quench their luminescence. Under these conditions, the reversible transformations of photochromic ligands or the irreversible cleavage of photocaged counterparts translates into the possibility to switch luminescence with external control. As an alternative to regulating the photophysics of a quantum dot via the photochemistry of its ligands, the photochemistry of the latter can be controlled by relying on the photophysics of the former. The transfer of excitation energy from a quantum dot to a photocaged ligand populates the excited state of the species adsorbed on the nanocrystal to induce a photochemical reaction. This mechanism, in conjunction with the large two-photon absorption cross section of quantum dots, can be exploited to release nitric oxide or to generate singlet oxygen under near-infrared irradiation. Thus, the combination of semiconductor quantum dots and photoresponsive ligands offers the opportunity to assemble nanostructured constructs with specific functions on the basis of electron or energy transfer processes. The photoswitchable luminescence and ability to photoinduce the release of reactive chemicals, associated with the resulting systems, can be particularly valuable in biomedical research and can, ultimately, lead to the realization of imaging probes for diagnostic applications as well as to therapeutic agents for the treatment of cancer.
光致变色或光笼配体可以锚定在半导体量子点的外壳上，以便用光刺激来控制这些无机纳米晶体的光物理性质。光响应配体的两种互变状态之一可以设计为从激发的量子点接受电子或能量，并猝灭它们的发光。在这些条件下，光致变色配体的可逆转化或光笼对应物的不可逆断裂转化为用外部控制切换发光的可能性。作为通过配体的光化学反应来调节量子点的光物理性质的替代方法，可以依靠前者的光物理性质来控制后者的光化学反应。从量子点到光笼配体的激发能转移将物种的激发态填充到吸附在纳米晶体上的物种上，以引发光化学反应。这种机制与量子点的大双光子吸收截面相结合，可以在近红外辐射下释放一氧化氮或产生单线态氧。因此，半导体量子点和光响应配体的结合提供了机会，可以基于电子或能量转移过程组装具有特定功能的纳米结构构建体。与这些系统相关的光致变色发光和光诱导释放反应性化学物质的能力在生物医学研究中特别有价值，并最终可以实现用于诊断应用的成像探针以及用于治疗癌症的治疗剂。
