Volume 3, Issue 3

Spectroscopic ellipsometry (SE) is a powerful technique for the characterization of materials, which is able to probe in a sensitive way their nanostructure as well as to get rich information about their dielectric properties, through the interaction of polarized light with matter. In the present trend of developing functional advanced materials of increasing complexity for a wide range of technological applications, works involving SE have flourished and have been reported in an increasing number of articles, reviews, and books. In this context, the aim of this paper is to provide for those among material scientists who are not SE specialists, a concise and updated overview of the capabilities of SE for the characterization of the so-called nano- and metamaterials, especially those presenting active functionalities. Key aspects for a reliable material characterization by SE are given: choice of the setup and measurement conditions, measurement accuracy, definition of a model, sensitivity to parameters. Also, very recent works involving SE are highlighted, especially those dealing with the development of building block materials for optimized or active plasmonics applications, the still ongoing exploration of small-size effects on the dielectric response of matter, the characterization of metamaterials, and the design of detectors with improved accuracy based on coupling of the phase sensitivity of SE with metamaterials engineering.

Advances in bionanotechnology promise to allow medical diagnosis and therapy through the channel of molecular imaging. Combining biological science and modern detection techniques, molecular imaging has the ability to penetrate biomedical processes at the molecular and cellular level. Magnetic nanoparticles (MNP), broadly defined as particles of tens of nm to approximately 2 μm in diameter in this review, are playing an increasingly important role in molecular imaging. They act as contrast agents to remarkably enhance the signal. The precise determination of the position and quantity of MNP is critical for these applications. This review describes the advances in the development of detection techniques for magnetic particles used in molecular imaging and diagnosis. The techniques are categorized as high magnetic field techniques and low magnetic field techniques. The high-field studies focus on magnetic resonance imaging (MRI). The ultra-low-field (ULF) studies include several of the most recent techniques: giant magnetoresistance sensors, superconducting quantum interference devices, atomic magnetometers, and magnetic particle imaging. The advantages and disadvantages of each method are discussed.

Gold nanoparticles have emerged as a promising material for biomedical research due to ease of synthesis and highly adjustable optical properties, which can be utilized in the imaging of different diseases. Gold nanoparticles are fabricated by grafting biocompatible polymers and natural or synthethic biomolecules and present a novel avenue for engineering multifunctional smart systems. Many reports on the significant achievements and the bioconjugation chemistry promise to expand the application spectrum of gold nanoparticles. This review summarizes the current state-of-the-art development of functionalized gold nanoparticles for cancer gene therapy.

Bionanotechnology is the field dealing with the synthesis and application of different nanomaterials. Nanoparticles usually form the core of nanobiomaterials. For the past decade, a variety of inorganic nanoparticles have been newly created to provide superior material properties. Nowadays, synthesis of nanoparticles is the area of interest due to their physical, chemical, optical, electronic properties, and most importantly their larger surface area-to-volume ratio. Synthesis of inorganic nanoparticles is done by various physical and chemical processes, but biological route of synthesis is gaining more importance due to their eco-friendly nature. Bioactivity of nanoparticles broadly involves the wide range of nanoparticles and their biological application. They have been used as new tools not only for investigation of biological processes but also for sensing and treating diseases. In this respect, they are appearing to be novel antimicrobial agents even against drug-resistant microorganisms. On the other side at higher concentration, they show toxicity to the humans and ecosystem. Therefore, in the present review, we have briefly described the synthesis of different metal nanoparticles by different approaches mainly paying attention to their biosynthesis, antimicrobial activity, and cytotoxicity. As silver nanoparticles are finding many applications among all of the inorganic nanoparticles, we paid special attention to them, too.

Recent investigations into atomically precise gold clusters show that not all magic-numbered clusters can be readily obtained through conventional synthetic routes. For example, Au 21 (SR) 14 , a magic-numbered cluster, was only obtained as a minor product from a mixture of clusters but was never synthesized in pure form using a single-step synthetic approach. We have made several attempts, albeit without any success, using a variety of approaches to synthesize Au 21 (SR) 14 clusters in a single step. We show in this communication that synthetic failure is not likely due to electronic instabilities based on computational investigation of its electronic structure. Our DFT calculations show that the optimized cluster consists of a center Au 13 core cluster capped by two Au 2 (SCH 2 CH 3 ) 3 fragments and four Au(SCH 2 CH 3 ) 2 fragments and is energetically stable. The findings reported here should give more confidence for the synthetic chemists to successfully synthesize Au 21 (SR) 14 in the near future.