Confining visible light for an efficient Photocatalytic Process

At present, our prime energy source is coal. As the burning of coal emits hazardous gases, we need a clean alternate energy source. Sunlight shines upon us from morning to afternoon. We can collect the sunlight, convert it, and store it in the form of electric or chemical energy. These transformed energies are renewable and clean. However, to do so, we require materials that can capture the whole range of sunlight ranging from UV-visible to near infra-red (NIR). We are developing two-dimensional (2D) carbon-based layered materials for harvesting solar light. One of our innovative approaches is to use plasma for synthesizing atomically thin graphitic carbon nitride nanosheets. Plasma, discharged in air, contains numerous neutral and ionized species, such as N2, OH, NO2, N2O, NO3. These ionized species diffuse in water, move into the separation between layers and exfoliate the layers. This method is simple and a green approach for getting a few layered materials. These few-layered carbon nanomaterials are useful in harvesting a large portion of visible light. However, they cannot amplify the incident light intensity. Light amplification is accomplished using metal nanoparticles. Metal nanoparticles show unique absorption in the visible region known as surface plasmon resonance (SPR). The absorption is tunable, as we can shift the spectral position from visible to near infra-red by changing the size and shape of the nanoparticles. These metal nanoparticles can collect weak intensity photons, accumulate the photons at the nearest metal nanoparticle gap, and build up largely amplified photon intensity. These build-up photons are finally utilized to drive photochemical water splitting, water purification using a green laser. 

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Dr.Biswajit Choudhury