Dr. Ali Halake Wako
Name: Dr. Ali Halake Wako
Department: Physical Sciences
Area of Specialization: Materials Science Engineering, Nanotechnology, Solid State Physics and Condensed Matter Physics
Contact Address: P.O. BOX 6- 60100, Embu (Kenya).
Dr. Ali Halake Wako holds a PhD degree in Physics from the University of the Free State (South Africa). He also holds a Master of Science (MSc) degree in Physics from the same university. His area of specialization is Materials Science and Nanotechnology. Dr. Ali has published eleven (11) research journals on the synthesis, characterization and fabrication of doped nanomaterials for industrial applications in the manufacture of Semiconductors, Thin films, Lighting and display devices like fluorescence lamps, plasma display panels (PDP) and White light-emitting diodes (WLEDs) for white light production.
Phosphor Technology (Nanotechnology/Materials Science)
Phosphor technology and nanotechnology forms the basis of my research. A phosphor is a solid material that emits light (luminescence) when exposed to radiation such as ultraviolet light (UV), visible light, thermal radiation (heat) or a beam of electrons or photons. Luminescence is a phenomenon by which a substance emits electromagnetic radiation following excitation by electrons or photons. A phosphor (luminescent material) can be crystalline or amorphous and
consists of a host lattice and one or more activators (dopants) ranging in amounts from parts per million to a few mole percent. Both the host and activator are responsible for the luminescent properties of a phosphor. Phosphors are generally powders having average particle sizes ranging from nano-scale (10-9) to
micro-scale (10-6). Phosphor may also be in thin film form. When the particle size reaches nano scale, new properties are observed like the blue shift of emission intensity i.e. when the diameter of a particle is reduced the band gap (Eg) is blue-shifted due to the effect of quantum
Luminescence can be divided into two broad categories viz: By duration (fluorescence or phosphorescence) or by the mechanism that creates the light i.e. the type of excitation sources (chemical reactions, electrical energy, subatomic motions, or stress on a crystal, thermal etc). Phosphor technology includes all the techniques of manufacturing phosphors (both in small scale and large scale), characterization and application. Nanotechnology refers to the process of
harnessing and applying principles of nanoscience in the synthesis and manufacture of nanomaterials and devices. The development of nanoscience and nanotechnology so far has been made possible by the success in the production of nanomaterials. The preparation of nanomaterials involves control of size, shape and structure of the materials. During the past few years, nanoparticles of materials have been produced in large quantities by use of physical and chemical technique. The scientific
preparation of nanomaterials such as phosphors, ceramics and semiconductor devices include various synthesis techniques like co-precipitation, sol-gel, combustion method and solid stateISO 27001:2013 Certified Knowledge Transforms ISO 9001:2015 Certified reaction among others. Thin film growth technology which include Chemical Bath Deposition (CBD), Pulsed Laser Deposition (PLD) and Spin-Coating are techniques used for the fabrication of advanced and smart electronic devices such as Solar panels, optical and Corrosion resistant coatings.
Characterization involves application of spectroscopic techniques such as Energy Dispersive Xray Spectroscopy (EDS), Auger Electron Spectroscopy (AES), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-Vis Spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Time-of-flight secondary ion mass spectroscopy (TOFSIMS), Fourier Transform Infra-Red (FTIR) Spectroscopy, Photoluminescence Spectroscopy (PL), Fluorescence Spectroscopy, Thermoluminescence Spectroscopy (TL), Electron Paramagnetic Resonance (EPR) and Electron Spin Resonance (ESR) among others to study the properties of nanomaterials. Persistent luminescence materials with high quantum efficiency and exhibit high stability, brightness and versatile industrial processing characteristics are suitable for manufacture of lighting and display devices such as in the production of fluorescent tubes, television screens, computer monitors, emergency and exit signs, light emitting diodes (LEDs), safety indicators in textiles, luminescent paints, optical data storage and dial plate of glow watches. In addition, this interdisciplinary technology has a lot of applications in pharmaceutical industry, medical diagnosis, meteorology, building materials and motor vehicle industry.