ELECTRONIC AND OPTICAL PROPERTIES OF BORON NITRIDE NANOTUBES (BNNTS) AS SUNSCREEN ACTIVE SUBSTANCE USING DENSITY FUNCTION THEORY (DFT)

• Main Author: Jonuarti, Riri
• Format: Dissertations
• Language: Indonesia
• Subjects: Fisika
• Online Access: https://digilib.itb.ac.id/gdl/view/47546
• Institution: Institut Teknologi Bandung

In this research, an application of BNNT material has been investigated in the field of sunscreen which is a novelty of BNNT research. The investigation was implemented in an experimental work such as making the sunscreen gel with the active ingredient BNNT in a mixture of basic formulas that is Carbomer which contains a concentration of Carbopol as much as 1% w/w. Furthermore, the sunscreen gels were characterized using UV absorption spectroscopy to determine the absorbance spectra of the sunscreen in the ultraviolet (UV) and visible light regions. In addition, diffuse reflectance spectroscopy was used to determine the percentage of reflectance of sunscreen in the UV and visible light areas. Base on the two characterizations, it was obtained that the sunscreen gel with BNNT as an active ingredient has a maximum absorbance in the UV region. The concentration of BNNT in the Carbomer basic formula (Carbopol 940 1% w / w) affects the height of the absorbance peak. While, the reflectance of these sunscreen gels does not depend on the concentration of BNNT in the basic formula. All of four samples showed a reflectance percentage at almost the same level in both the UV and visible light regions. Overall, the experimental results stated that BNNT with a concentration of 1% w/w on the basic formula is a sunscreen gel formula that has the best absorbance in the UV region and large transparency in the visible light region. Thus, sunscreen gel with BNNT material has the opportunity to be developed in the future with further testing. Hereinafter, The structural, electronic and optical properties of the hexagonalboron nitride (h-BN) in general and the ultra-small boron nitride nanotube (BNNT) have been successfully investigated using the density functional theory (DFT) method within a software called vienna ab-initio simullation package (VASP). H-BN shows honey combs shaped structure like graphene. In contrast to graphene which has electronic properties depending on its geometry, the results of calculations in this study show that h-BN is an insulator with a wide band gap and is not related to the dimensions and size or even the number of layers. The calculation results of the optical properties indicate that h-BN has maximum dispersion and maximum absorption in the UV energy region. Then, the structures of the ultra-small BNNT are built from h-BN sheets. By considering to the chiral vector (n1, n2) when rolling a h-BN sheet, then it will generate the ultra-small (n, 0) zigzag and the ultra-small (n1, n2) armchair BNNT, with n = 3, ..., 10 for the zigzag structure, and n1 = n2 = n where n = 2, ..., 10 for the armchair structure. Besides the study of the ultra-small BNNT can be called a fresh study, the ultra-small BNNT structures are very interesting to investigate because they have very different characteristics from the characteristics of BNNT with a diameter of larger than 0.95 nm. The results of calculations using the DFT method and local density approximation (LDA) as the potential exchangecorrelation, show that the ultra-small zigzag and the ultra-small armchair BNNT have unique electronic properties. The ultra-small BNNT has an energy band gap which depends on the geometry of its structure such as the chirality and diameter of the nanotube. As for the optical property of the ultra-small BNNT structure, it also depends on the structure geometry, but it is not too significant. In addition, defects (replacing B and N atoms with C atoms) in the ultra-small zigzag and the ultra-small armchair of BNNT, give important significance to the electronic and optical properties of these ultra-small materials. Defect given will shift the electronic property (narrowing the energy band gap) and optics (shifting the absorption peak into the infra-red energy region) of the ultra-small BNNT. Thus, the BNNT ultra-small material is very promising for new applications because the energy band gap can be tuned, and the absorption area of the BNNT ultra-small material can be shifted by changing the tube diameter in the range of ? 9.5 nm and with atoms C as a defect in the ultra-small structures.