The functionalization of nanoscale materials with stimuliresponsive components is an important tool for mimicking the functions of biological systems and conversion of external inputs to useful signals.[1-4] Recently, we reported the conductance switching of individual single-walled carbon nanotube transistors (SWNTTs) functionalized by photochromic molecules. The switching can be toggled back and forth between different conformations and is driven by external stimuli.[5, 6] Herein, we report a combination of microfabrication and molecular self-assembly to produce functional devices formed from individual single-walled carbon nanotube field-effect transistors that are coated with photoactive TiO2 quantum dots (Figure 1a). These studies utilize the inherent ultrasensitivity of SWNTTs that arises from their active surface being exposed to the environment, and is the basis for new types of sensors [1-3, 5-8] and optoelectronic devices.[8-25] Importantly, the p-type semiconducting tubes show a large rapid conductance decrease upon exposure to UV light, the decrease reverses when the UV irradiation is switched off. In contrast, the mirror-image photoswitching effects are seen for ambipolar tubes when the negative and positive gate fields are applied.