Adjustable photoluminescence of peptide nanotubes coatings

Peptide nanotubes (PNTs) have become a significant subject at the biological and bionanotechnology field. Here we describe the spectroscopic analysis of PNTs coatings, which were deposited by a physical vapor deposition technology. We show that we can adjust the electronic, and consequently the spectroscopic, photoluminescence (PL) properties of the PNT coatings, simply by changing the parameters of the PNT deposition. We show that by controlling the PNT deposition parameters we can observe different PL properties of the PNT coatings and significantly strengthen the PL in the visible blue region. We further explain that the strong blue emission is resulting from the conversion of the monomers to a different chemical structure. The strong blue emission, and our ability to adjust it, promotes the use of the PNTs as organic materials for light emitting devices.     

Effect of Surface Coating on the Photocatalytic Function of Hybrid CdS–Au Nanorods

Hybrid semiconductor–metal nanoparticles are interesting materials for use as photocatalysts due to their tunable properties and chemical processibility. Their function in the evolution of hydrogen in photocatalytic water splitting is the subject of intense current investigation. Here, the effects of the surface coatings on the photocatalytic function are studied, with Au‐tipped CdS nanorods as a model hybrid nanoparticle system. Kinetic measurements of the hydrogen evolution rate following photocatalytic water reduction are performed on similar nanoparticles but with different surface coatings, including various types of thiolated alkyl ligands and different polymer coatings. The apparent hydrogen evolution quantum yields are found to strongly depend on the surface coating. The lowest yields are observed for thiolated alkyl ligands. Intermediate values are obtained with L‐glutathione and poly(styrene‐co‐maleic anhydride) polymer coatings. The highest efficiency is obtained for polyethylenimine (PEI) polymer coating. These pronounced differences in the photocatalytic efficiencies are correlated with ultrafast transient absorption spectroscopy measurements, which show a faster bleach recovery for the PEI‐coated hybrid nanoparticles, consistent with faster and more efficient charge separation. These differences are primarily attributed to the effects of surface passivation by the different coatings affecting the surface trapping of charge carriers that compete with effective charge separation required for the photocatalysis. Further support of this assignment is provided from steady‐state emission and time‐resolved spectral measurements, performed on related strongly fluorescing CdSe/CdS nanorods. The control and understanding of the effect of the surface coating of the hybrid nanosystems on the photocatalytic processes is of importance for the potential application of hybrid nanoparticles as photocatalysts.     

Eradication of Multi‐Drug Resistant Bacteria by a Novel Zn‐doped CuO Nanocomposite

Zinc‐doped copper oxide nanoparticles are synthesized and simultaneously deposited on cotton fabric using ultrasound irradiation. The optimization of the processing conditions, the specific reagent ratio, and the precursor concentration results in the formation of uniform nanoparticles with an average size of ≈30 nm. The antibacterial activity of the Zn‐doped CuO Cu_0.88Zn_0.12O in a colloidal suspension or deposited on the fabric is tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) bacteria. A substantial enhancement of 10 000 times in the antimicrobial activity of the Zn–CuO nanocomposite compared to the pure CuO and ZnO nanoparticles (NPs) is observed after 10 min exposure to the bacteria. Similar activities are observed against multidrug‐resistant bacteria (MDR), (i.e., Methicillin‐resistant S. aureus and MDR E. coli) further emphasizing the efficacy of this composite. Finally, the mechanism for this enhanced antibacterial activity is presented.     

Antibacterial,Antibiofilm, and Antiviral Farnesol-Containing Nanoparticles Prevent Staphylococcus aureus from Drug Resistance Development

Multidrug antimicrobial resistance is a constantly growing health care issue associated with increased mortality and morbidity, and huge financial burden. Bacteria frequently form biofilm communities responsible for numerous persistent infections resistant to conventional antibiotics. Herein, novel nanoparticles (NPs) loaded with the natural bactericide farnesol (FSL NPs) are generated using high-intensity ultrasound. The nanoformulation of farnesol improved its antibacterial properties and demonstrated complete eradication of Staphylococcus aureus within less than 3 h, without inducing resistance development, and was able to 100% inhibit the establishment of a drug-resistant S. aureus biofilm. These antibiotic-free nano-antimicrobials also reduced the mature biofilm at a very low concentration of the active agent. In addition to the outstanding antibacterial properties, the engineered nano-entities demonstrated strong antiviral properties and inhibited the spike proteins of SARS-CoV-2 by up to 83%. The novel FSL NPs did not cause skin tissue irritation and did not induce the secretion of anti-inflammatory cytokines in a 3D skin tissue model. These results support the potential of these bio-based nano-actives to replace the existing antibiotics and they may be used for the development of topical pharmaceutic products for controlling microbial skin infections, without inducing resistance development.     

Modeling a grid‐connected concentrator photovoltaic system

A six‐parameter formula is proposed for describing the hourly alternating current performance of a grid‐connected, passively cooled concentrator photovoltaic (CPV) system. These system parameters all have physical meanings, and techniques are described for deriving their numerical values. The predictions of the model are compared with the measured output of a Soitec CPV system at Sede Boqer and found to be accurate to approximately ± 5% at all times of the year. The model should also be valid for systems of similar construction operated in different climates from the system studied here, and also for passively cooled CPV systems of different designs provided that suitable numerical values are determined for their system parameters. Another possible use of the model is as a guide for tailoring CPV cell architecture to the particular spectral conditions of the locations in which they will operate. Attention is drawn to the fact that the numerical values of some of the system parameters are found to depend upon the time binning employed for the data. An explanation is given for this phenomenon, which is also found to occur for non‐concentrating photovoltaic panels. Copyright © 2014 John Wiley & Sons, Ltd.     

Functional Carbon Quantum Dots for Ocular Imaging and Therapeutic Applications

Carbon quantum dots (CDs) are a class of emerging carbonaceous nanomaterials that have received considerable attention due to their excellent fluorescent properties, extremely small size, ability to penetrate cells and tissues, ease of synthesis, surface modification, low cytotoxicity, and superior water dispersion. In light of these properties, CDs are extensively investigated as candidates for bioimaging probes, efficient drug carriers, and disease diagnostics. Functionalized CDs represent a promising therapeutic candidate for ocular diseases. Here, this work reviews the potential use of functionalized CDs in the diagnosis and treatment of eye-related diseases, including the treatment of macular and anterior segment diseases, as well as targeting Aβ amyloids in the retina.