Analyzing UV-Vis spectra to understand the performance variations of the photocatalysts

NATIONAL SCHOOL POLYTECHNIC OF CONSTANTINE
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MATERIALS ENGINEERING

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REALIZED BY :       

• BOUCHETOB Oussama
• BOUDJOUDJOU Ghada
• ZIDANE Oumaima
• BOURA Taki ahmed
• HADDAD Mouna
• BOUCHAREB Manar Wouroud

2023/2024

1. INTRODUCTION :

The energy levels, particularly the bandgap width, of semiconductor-based catalysts affects their ability to absorb light and catalyze ecologically beneficial chemical reactions through photocatalysis. The research focuses on analyzing UV-Vis spectra to understand the performance variations of the photocatalysts.

1. OBJECTIVES OF THE EXPERIMENT :

  Determine the band gap energy of modified semiconductor photocatalysts using UV-Vis spectra.

1. SOME EXPLICATIONS:

Quantum well: is a thin layer, typically 5-20 nm thick, that confines particles like electrons or holes in one dimension while allowing movement in others. This confinement, a quantum effect, affects the density of states and is often achieved using semiconductor layers with wider band gaps. Quantum wells are crucial in optoelectronic devices like laser diodes and can be further enhanced with strain or used in multiples for increased optical gain or absorption.

Quantum dots : are tiny semiconductor crystals, usually 2 to 10 nanometers wide, that can change the energy of light they absorb and emit. They have unique electronic properties, allowing them to adjust their energy levels based on their size, which affects their color emission.

Artificial atoms: replicate natural atoms' properties with enhanced control over physical and chemical traits, crucial for fundamental quantum research and crafting cutting-edge technologies like lasers, LEDs, and sensors. Their versatility holds immense promise across various domains, spanning from quantum computing to personalized medicine.

Diffuse reflection:is an optical phenomenon in which light is reflected in multiple directions from a rough or irregular surface. Unlike specular reflection, where light is reflected in a specific direction, diffuse reflection causes light to scatter in all directions. This creates a matt surface that is characteristic of unpolished or textured materials.

Specular reflectance :is the reflection of light at a specific angle, typically equal to the angle of incidence. It describes the amount of light reflected in a specific direction by a smooth, shiny surface.

Quantum confinement:refers to the phenomenon where the motion of charge carriers, such as electrons or holes, is restricted to a very small region in a material, leading to quantum effects influencing their behavior. This confinement alters the energy levels and properties of the carriers, often resulting in unique optical and electronic properties in nanoscale structures.

1. DETERMINE THE EG OF DEFFIRENT MATERIALS:    

Determine Eg: The band gap energy (Eg) can be calculated from the absorption edge using the equation Eg = hc/λ, where λ is the wavelength corresponding to the absorption edge.

We find that the sample X is the CdS-2 , the same Eg.

CdS:  has an absorption edge at around 535 nm (2.28 eV). This means that it only absorbs light with wavelengths shorter than 535 nm, and light with wavelengths longer than 510 nm is transmitted.

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