Maria Angela Nitti

Metal nanoantimicrobials for textile applications

Abstract Research on the nanomaterials containing one or more transition metals is growing tremendously, thanks to the large number of preparation processes available and to the novel applications that can be envisaged in several fields. This review presents an overview of the selected studies in the field of antimicrobial textiles, employing bioactive nanophases of elements/compounds such as silver, copper, or zinc oxide. In addition, the history of use of these antimicrobials and their mechanism of action are shortly reported. Finally, a short description is provided of the deposition/preparation methods, which are being used in the authors’ labs for the development of the textiles modified by the novel nanoantimicrobials.

Influence of bias voltage on the stability of CsI photocathodes exposed to air

Abstract We describe a possible correlation between the bias voltage applied to the substrate during the growth of CsI photocathodes and the variation of quantum efficiency (QE) after one day exposure to humid air. It was found that fresh samples are much less sensitive to humid air when a high negative bias voltage was applied during film growth. A model based on surface film interaction with water molecules is presented for the observed effect. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements have been performed to examine, respectively, the bulk structure and the surface of fresh and exposed CsI samples. Also reported are transmittance measurements for fresh and aged CsI samples in the wavelength range 190– 850 nm .

Influence of the substrate reflectance on the quantum efficiency of thin CsI photocathodes

Abstract Performance of thin CsI films operated, at the same time, as reflective and semitransparent photocathodes is presented. Photoemission properties have been analysed on CsI films deposited on aluminium substrates made out of either polished disks or thin films evaporated onto fused silica disks. A comparison between measured values of quantum efficiency (QE) of such photocathodes and the QE of traditional reflective photocathodes is presented.

Spray deposited carbon nanotubes for organic vapor sensors

In this paper a study of chemiresistor sensors based on Single Wall Carbon Nanotube films deposited at low temperature by means of a spray technique is presented. A nanodispersion of nanotube powder in a non-polar 1,2-Dichloroethane solvent was used as starting solution. Electron Microscopy in Scanning and Transmission mode were used in order to verify the morphological properties of the deposited films. Conductivity of single walled carbon nanotubes (SWNTs) were measured in various organic solvent vapours environments. The solvents used are characterized by different polarities and volume fractions of saturated vapours defined by the vapour pressure. The results show that the electrical resistance of the sensors increases when exposed to solvent vapours. Finally the effect of Teflon-like coating on the sensitivity yield is presented and discussed.

Photodetectors based on carbon nanotubes deposited by using a spray technique on semi-insulating gallium arsenide

Summary In this paper, a spray technique is used to perform low temperature deposition of multi-wall carbon nanotubes on semi-insulating gallium arsenide in order to obtain photodectors. A dispersion of nanotube powder in non-polar 1,2-dichloroethane is used as starting material. The morphological properties of the deposited films has been analysed by means of electron microscopy, in scanning and transmission mode. Detectors with different layouts have been prepared and current–voltage characteristics have been recorded in the dark and under irradiation with light in the range from ultraviolet to near infrared. The device spectral efficiency obtained from the electrical characterization is finally reported and an improvement of the photodetector behavior due to the nanotubes is presented and discussed.

Role of the substrate reflectance and surface-bulk treatments in CsI quantum efficiency

Abstract We have experimentally investigated the following aspects related to the quantum efficiency of CsI photocathodes: the type of substrate, the film thickness and the effect of a “bulk treatment” during the film growth. We discovered that, using a high reflectivity aluminium substrate, the photoemission of very thin CsI film is enhanced. Our study also revealed that photocathodes become less sensitive to moisture when a negative bias voltage is applied to the substrate during the film deposition process.

Nonconventional Routes to Silver Nanoantimicrobials: Technological Issues, Bioactivity, and Applications**This chapter was prepared by three research groups that equally contributed to the work. The first author listed for each institution represents the first author for his/her own research group. Mauro Pollini and Federica Paladini contributed equally to this chapter.

Silver antimicrobial nanomaterials are the subject of exponentially increasing attention in both academia and industry because of their unprecedented efficiency in preventing biocontamination in several real-life applications. Wet chemical syntheses based on redox processes in micellar media as well as plasma or magnetron sputtering methods are dominating the fields of chemical or physical preparations of silver nanoparticles (AgNPs), respectively. The authors of this chapter are experts in three nonconventional methods producing outperforming AgNPs, either as nanocolloids or as multifunctional thin coatings. Electrochemical synthesis of AgNP colloids, ion beam sputtering, and photo-assisted deposition of AgNP-based coatings are reviewed in the present chapter. Technological insights into the processes are offered to the specialized audience, and an overview of the most widely accepted bioactivity mechanisms and the most promising applications is provided.