**Chapter 7 125** Diluted Magnetic Semiconductors Nanocrystals: Saturation and Modulation *by Anielle C.A. Silva, Amanda I.S. Barbosa, Alessandra S. Silva, Elisson A. Batista, Thaís K. de Lima Rezende, Éder V. Guimarães, Ricardo S. Silva and Noelio O. Dantas* **Section 3**

Preface

One nanometer is a billionth of a meter. When the size of at least one of the dimensions of orderly arranged atoms in three-dimensional space is less than 100 nm it is called a nanocrystal. Nanocrystals do not follow the law of classical mechanics as they enter the quantum realm. The reduction in size causes the surface area to increase in comparison to their volume, which helps to enhance their mechanical, thermal and catalytic properties. For example, gold nanocrystals produce different colors in their colloidal suspensions as their sizes vary, thus they can be used as color-changing cosmetics in the beauty product industry. Gold nanocrystals are already in use as labels in electron microscopy for biological samples or as drug carriers, tumor detectors, inter-cellular delivery vehicles in gene therapy, radiotherapy dose enhancers, and more. The biomedical, as well as chemistry and physics fields, benefit immensely from the numerous applications of nanocrystals. Nanodimensional rotors and motors are now being fabricated for producing power inside nanoelectromechanical systems (NEMS), integrated with nanotransistors. Atomic force microscopy (AFM) tips are used for detecting stress and vibration at the atomic level. Graphene, carbon nanotubes (CNTs), and diamond are the materials that form such nanocrystals in NEMS applications. Self-assembled monolayers (SAMs) are formed by organic molecules with their heads attaching to the substrate while functional groups like thiols and silanes are kept away from the surface. In this way, they can form two- or three-dimensional superlattices. Nanocrystals are also very important for understanding the Covid-19 pandemic. The size of the virus varies from 50 nm to 200 nm. The coronavirus is a protein membrane encapsulated nucleocapsid (N) protein and RNA genome with about 20-nm long spike proteins all around them. To fight the virus humans have to

develop medicines and vaccines, which again, are made up of nanocrystals.

and engineering who study nanocrystals.

This book contains chapters written by researchers in biology, chemistry, physics,

**Dr. Awadesh Kumar Mallik**

IMO-IMOMEC, Hasselt University, Diepenbeek, Belgium


Antimicrobial Efficacy of Biogenic Silver and Zinc Nanocrystals/ Nanoparticles to Combat the Drug Resistance in Human Pathogens *by Gulzar Ahmed Rather, Saqib Hassan, Surajit Pal, Mohd Hashim Khan, Heshu Sulaiman Rahman and Johra Khan*
