Size Dependence Of Electronic Structure Research Articles

Nanoparticles. By Raz Jelinek. De Gruyter, 2015. Pp. 283. Price EUR 69.95. ISBN 9783110330021.

As the title indicates, the book ‘Nanoparticles’ by R. Jelinek deals with objects at the nanometric scale. As nanoscience and nanotechnology devoted to nanoparticles represent an ‘enormous scope’, carboneous nanomaterials and preparation processes like lithography are excluded from the content. The aim of this book is to give an overview of nanoparticles to a reader who is not necessarily active or an expert in this discipline. This overview is given through selected examples of nanoparticle applications, with a preference given to biomedical ones. With such a generic title as ‘Nanoparticles’ (NPs), the reader may be misled about its contents. Indeed, does it just talk about objects with a nanometric scale or objects for which a specific property arises from their nanometric size? That is the first question to ask when nanoparticles are concerned. In the first case, all kinds of solid nanoscale compounds are concerned whereas in the second one, only the compounds related to the nanosciences and nanotechnology fields fall under the scope of this book. The aim of this book is to serve as a ‘starting point’ for further investigation in the field of nanoparticles ‘with a methodical summary of the field – how concepts, synthesis schemes and applications of NPs have been developed and implemented’. So a clear definition of the term ‘nanoparticles’ can rightly be expected, but in the introduction we learn that ‘the precise definition of NPs may be somewhat fluid’. Then the term ‘nanoparticles’ is defined as ‘atomic and molecular aggregates which are generally smaller than tens of nanometers’. It is worth noting that in the preface this definition concerns only ‘atomic aggregates’ presenting unique properties due to their nanometric dimensions. After a brief introduction of the book and description of ‘historical context and early work’ (Chapter 1), the next three chapters deal with inorganic nanoparticles and constitute the main part of the book with 177pp. Chapter 2 introduces bandgap theory with the size-dependence of electronic structure and ‘Semiconductor nanoparticles’. Different chemical compositions and morphologies of nanoparticles are presented through applications in biosensing, solar cells and photonics fields. However, different points like solar cell efficiency, interest of NPs’ chemical composition or morphology are not discussed in detail and do not allow the reader to really appreciate the impact of nanoparticles on these specific fields. Chapter 3, which is the most prominent one (85 pp), deals with metallic nanoparticles and focuses mainly on gold nanoparticles. The choice of gold nanoparticles allows the introduction of the concept of localized surface plasmon resonance in an easy way. The synthesis of spherical gold nanoparticles is briefly presented, followed by the application of gold nanoparticles in different fields such as sensing and catalysis. Then, gold nanorods/nanowires are rapidly introduced, followed by a survey of other morphologies of gold nanoparticles–nanoprisms and polyhedral, hollow and branched nanoparticles. The reader has to wait until section 3.2 about silver nanoparticles and section 3.3 about noble metal and transition metal nanoparticles to obtain a better understanding of metallic nanoparticle synthesis thanks to figures depicting the formation of different nanoparticle shapes during the nanoparticles’ growth process. The last section, 3.4 ‘Hybrid nanoparticles’, shows a large range of possibilities, namely alloy, core-shell metal and Janus nanoparticles. Metal and metalloid oxide nanoparticles are introduced in Chapter 4 (45 pp), which is easy to follow thanks to its structure: the different sub-sections start with the presentation of the type of metal oxide, followed by an explanation of how nanoparticles can be prepared and finish with examples of their potential applications. ISSN 2052-5206

Size dependence of Zn 2p 3∕2 binding energy in nanocrystalline ZnO

The experimental results in size dependence of electronic structure and optical band gap show that the nanocrystalline ZnO has two binding states which energies are lower than that of the bulk ZnO. This size dependence of binding states is associated with the number of broken bonds of the individual Zn ion, which could be modified by size reduction in nanoscale. Varying the number of broken bonds on the surface and the underneath layer might result in possible complications in the electronic structure of the nanocrystalline ZnO, thus giving rise to different optical properties rather than those relating to quantum size effects.

Size dependence of electronic structure and adiabatic type of collective vibration in small metal clusters.

The electronic structure of atomic clusters is studied as a function of the geometrical parameters and number of atoms N in the clusters. Self-consistent electron wave functions and energies are calculated for the clusters with closed and open shells for N ranging from 4 to 40 and for the various radii of positive cluster cores. These calculations are done both for the homogeneous and inhomogeneous jellium models of the cluster core. The equilibrium values of jellium core radius have been obtained using ab initio Hartree-Fock calculations for the valence electrons. The importance of the role of nonlocal exchange interaction in the creation of the equilibrium cluster structure is also shown. An adiabatic type of collective vibration mode is predicted. Vibrational freuqencies and amplitudes are calculated for the ``magic'' number clusters. The influence of the geometrical parameters on the physical properties of clusters is discussed.