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Electronic speckle pattern interferometry and related techniques using digital still cameras
(© 2007 Nova Science Publishers, Inc., 2007) Abedin, K.M.; Haider, A F M Yusuf; Department of Mathematics and Natural Sciences, BRAC University
Laser-induced breakdown spectroscopy and its applications in mineral and pollution analyses
(© 2012 Nova Science Publishers, 2012-09) Haider, A F M Yusuf; Abedin, K.M.; Department of Mathematics and Natural Sciences, BRAC University
Fabrication of silver nanoparticles by laser ablation technique: their characterization and uses
(© 2013 Nova Science Publishers, 2013) Haider, A F M Yusuf; Talukder, Aminul I.; Department of Mathematics and Natural Sciences, BRAC University
Nano structure materials have generated much interest in recent years. Nanotechnology involves the fabrication of particles at the nano scale level and subsequent use of those nano structure materials for better, more efficient and cost effective technology. Metal nanoparticles are more attractive because of their size dependent physical and chemical properties. Silver nanoparticles have advantage over all other metal nanoparticles because of their optical, electrical and thermal properties. A unique property of spherical silver nanoparticles is that the extinction peak of silver nanoparticles in water can be tuned over a range of 380 – 500 nm by changing the particle size. This chapter deals with colloidal solution of silver (Ag) nanoparticles in deionized nanopure water fabricated by Laser ablation technique without the use of any chemicals. The brilliant color of the colloidal solution of silver nanoparticles is different from the bulk silver. The spectral characterization and some morphological studies of these nanoparticles were done using UV-Vis spectroscopy and SEM/EDX experiments, respectively. The ablating laser pulse energy and the ablation time were the key parameters to control the size of the fabricated nanoparticles. It was observed that the size of nanoparticles decreases with increasing laser power and hence the UV-Vis spectra of the nanoparticles show a monotonic blue shift with ablating pulse power. The blue shift in the absorption spectra and a narrowing of the absorption line were also observed with increasing re-ablation time of already ablated silver colloids. Possible explanations of all these observations of fabricated silver nanoparticles are discussed in this chapter. The results of the study of the possible coagulation of the silver nanoparticle with passage of time after fabrication are also presented in this chapter. Besides its applications as conductive inks and pastes for their high conductivity, both electrical and thermal, silver nanoparticles for their unique optical properties, can be used in molecular diagnosis, textiles, photonic cells and in enhanced optical spectroscopic techniques such as metal-enhanced fluorescence (MEF) and surfaceenhanced Raman scattering (SERS). The use of silver nanoparticles in antimicrobial coatings, wound dressings and in biomedical devices/sensors have also generated great interest.
Generating near-field fresnel diffraction patterns by iterative fresnel integrals method: a computer simulation approach
(© 2012 Nova Science Publishers, Inc., 2012-12) Abedin, Kazi Monowar; Rahman, S.M.M.; Haider, A F M Yusuf; Department of Mathematics and Natural Sciences, BRAC University
Recently the concept of computer-based virtual experiments in all branches of physics has generated wide spread interests among the researchers. In this Chapter, we describe the Iterative Fresnel Integrals Method (IFIM), which is essentially a computer-based simulation method employing repeated calculation of Fresnel integrals to obtain the complete near-field Fresnel diffraction patterns or images from rectangular-shaped apertures in any given experimental configuration. The images observed in the far-field (the Fraunhofer regime) can be considered as a special case in this IFIM method. MATLAB codes are used to perform this Fresnel simulation in any personal computer, with a program execution time of the order of a minute. The IFIM method simulates a real diffraction experiment in a PC, and can also be a useful pedagogic tool to understand the details of the diffraction process. Here, we discuss the theoretical background of the method, as well as the complete implementation of the technique in MATLAB codes. Three specific applications of the iterative Fresnel integral method are considered in this Chapter: (a) single rectangular or square apertures, (b) double apertures and slits with arbitrary separations, and (c) square apertures tilted at an arbitrary angle to the optical axis. In each of these cases, the transition to the far-field (the Fraunhofer regime) is also simulated and discussed. Quantitative comparisons of the far-field intensity distributions with the analytic expressions from the Fraunhofer theory are made whenever possible. Double apertures in two dimensions, and apertures tilted simultaneously around two orthogonal axes are also briefly considered and simulated. Future possible extensions of the method to more complicated problems, such as multiple slits and diffraction gratings are also mentioned therein.
Gold nanoparticles: fabrication by laser ablation technique and their optical and morphological studies
(© 2013 Nova Science Publishers, 2013-01) Haider, A F M Yusuf; Department of Mathematics and Natural Sciences, BRAC University
Material particles of the size of few nano-meters to couple of hundreds of nano-meters exhibit size and shape dependent properties and the consequent versatility and importance in their use have made them an exciting and interesting field of research. Of these, noble metal nano-particles, particularly gold nano-particles have shown tremendous potential for their wide range of applicability not only in fundamental sciences like physics, chemistry and biology, but also in applied sciences such as in designing and developing varieties of nano-particle based devices and sensors. The number of articles published on noble metal nano-particles, particularly gold and silver nano-particles has gone up in exponential rate since the early nineties of the last century. One of the major thrust areas of nano-particles and their science and technology research are their fabrication. In the nineties of the last century and the first half of the last decade chemical methods dominated over all other methods, including the laser ablation technique which started emerging. The main disadvantage including a host of other drawbacks of conventional nano-particle generation techniques such as mechanical milling and grinding or even the chemical method like the sol-gel process is that it almost invariably picks up impurities which make them unusable and hence undesirable for many applications e.g. biological applications. Pulsed laser ablation is an attractive and a promising alternative, addressing the shortcomings of the conventional methods, including the chemical methods. In this chapter we discuss mostly about the nano-particle fabrication, with particular emphasis on gold nano-particles in colloids, using nano second laser pulses. A number of variables of the ablating laser pulse have been used to control the size of the fabricated nano-particles. These were done without the use of chemicals/chemical surfactants, which provided a good and clear understanding of the laser parameters on the control of the nano-particle size. Possible explanations of all observations are given.

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