The photodoping is attractive approach to readily tune the optical and electrical properties of metal oxide semiconductor nanoparticles or quantum dots and have found the extensive applications in optoelectronics, light harvesting and smart window devices for energy management. A key advantage of photodoping is that the optical and electronic properties can be easily tuned just by irradiating by light. We have demonstrated recently the TiO2 nanoparticle colloids in hole scavenging media that exhibit a stark response to UV light and enable to take control over the transmittance of window materials in the visible, near-infrared and even the thermal black body radiation part of the spectrum [1]. This is due to combined effects of localized surface plasmon resonance (LSPR) of photodoped electrons and absorption through the introduction of mid-bandgap states from Ti3+. The TiO2 nanoparticles can be reversibly bleached by withdrawing the electron by exposing to oxygen or by external bias in electrochromic smart window device.