Abstract UV-Vis technique is a compulsory technique for the optical study of the materials. Optical study helps the researcher for the application s of nanomaterials for different uses. Different devices are fabricat- ed on the basis of optical properties of the materials especially solar cells. With the help of this technique optical band gap can be calcu- lated which helps to choose the materials for the energy conversion purpose like light energy to electrical energy in solar cell. Also, from this technique purity of the sample can be measured by comparison with the reference solution. Here results of different materials are described which can help to better understand the analysis of Uv- Vis spectroscopy results. Keywords UV-VIS; Band gap; Nanoparticles Abbas, J Nanomater Mol Nanotechnol 2019, 8:3 DOI: 10.4172/2324-8777.1000268 Journal of Nanomaterials & Molecular Nanotechnology Understanding the UV-Vis Spectroscopy for Nanoparticles Qaisar Abbas* Introduction Ultra violet and visible (Uv-Vis) absorption spectroscopy is the technique by which we measure attenuation of light which passes through a under consideration sample or also after reflection from the sample. Both parts (Uv and Vis) of light are energetic that can excite electrons to higher energy levels [1]. Short Communication Principle of the Uv-Vis spectroscopy This follows the principle of the Beer lambert law which states that absorption of the light by the sample is directly proportional to the path length and concentration of the sample [2]. Mathematically, A=log (I0/I)=Ecl Where, A=absorbance I0=intensity of light incident upon sample cell I=intensity of light leaving sample cell C=molar concentration of solute L=length of sample cell (cm.) E=molar absorptivity Range Data provided in the given below Table 1. Explanation of the working When light falls on the sample each material absorbs a specific range of the light and shows the behavior accordingly. Electron from the atom excites towards the higher state from the lower energy state. These two states are classified in two types LUMO and HOMO. 1. LUMO : Lowest unoccupied molecular orbit 2. HOMO: Highest occupied molecular orbit. There are further classification of bonds and these bonds form according to the specific behavior of the sample which is being analyzed under the light. The details are shown in Figures 1 and 2. Sigma is stronger bond while pi is weak bond and it depends on the material which bond formed. The bond formation of organic materials is shown in Figure 3. Applications of the Uv-Vis spectroscopy The most important factor of the technique is its application for the researcher to give the information about the material when light falls on it. Detection of Chromophore functional group: To determine the functional group in the material exclusively it confirms the presence and absence of the Chromosphere in the sample which should be compound. Chromophore is an atom or group which is responsible of the color of the compound. Determine the unknown compound: With the help of the Uv-Vis spectroscopy unknown compound can be determined in the sample. For this purpose, required compound is compared to spectrum of the reference compound if luckily both the spectrum is matched then confirmation of unknown compound can be noted. Purity of the sample: The purity of the substance can be measured by this unique technique for this purpose absorption of the reference and the sample under observation is compared and via relative calculations of the absorption intensity purity of the sample can be confirmed. Band gap calculations: An interesting application of this technique is the calculations of the band via different method there are different software’s are available for this purpose. Mathematically: E=hc/λ (1) E=energy band gap h=planks constant, c=speed of light λ=wavelength *Corresponding author: Qaisar Abbas, Department of Physics, COMSATS University Islamabad, Lahore Campus 54000, Pakistan, E-mail: qaisar022@gmail.com Received: March 05, 2019 Accepted: May 16, 2019 Published: May 31, 2019 Table 1: Ranges of wavelength. International Publisher of Science, Technologyand Medicine All articles published in Journal of Nanomaterials & Molecular Nanotechnology are the property of SciTechnol, and is protected by copyright laws. Copyright © 2019, SciTechnol, All Rights Reserved. Short Communication A SciTechnol Journal Light Wavelength range in nm Ultraviolet 200-400 Visible 400-800