Transport phenomena in the mixed state and fluctuation regime in (Bi1.6Pb0.4)Sr2Ca1-x Hox (Cu1-yZny)2O8+d

Measurements of the magnetoresistivity, Seebeck, Nernst and Hall coefficients in Bi:2212 superconductors doped with Ho and Zn are reported. The critical temperature and the transport coefficients depend strongly on the Ho and Zn contents. The tails of the transport coefficients versus temperature curves are caused by fluctuation effects, which increase with increasing magnetic field. An anomalous suppression of superconductivity at x = 0.25-0.35 and y = 0.025-0.032 was also found when the hole concentration per Cu is PH = 1/8 and the transport properties exhibit metallic behavior. It was found that dBc2/dT = -2.4 ± 0.2 T/K, corresponding to a Ginzburg-Landau coherence length ε = 15 Å. The Hall resistivity ρxy scaling with the longitudinal resistivity ρxx as ρxy(T) = a-1ρα xx with α ≒ 1.8 is in agreement with the theory of Vinokur et al. The experimental data in the mixed state are in agreement with the prediction of the time-dependent Ginzburg-Landau theory

Synthesis, magnetic and transport properties of Ru1-xSb xSr2GdCu2O8 compounds

Polycrystalline samples with a nominal composition Ru1-xSb xSr2GdCu2O8 were prepared by a solid state reaction technique. A mixture of RuO2, Sb2O 3, Gd2O3, SrCO3 and CuO was used to obtain the samples. We performed X-ray diffraction analyses, DC susceptibility and transport measurements and the studies showed that the samples were almost pure Ru-1212 phase. We also observed that Sb doping reduce the conductivity of the system and the transition temperature decreases with increasing Sb content. This may be due to a distortion of RuO6 octahedral which is responsible for the increase of holes localization

Origanum vulgare mediated green synthesis of biocompatible gold nanoparticles simultaneously possessing plasmonic, antioxidant and antimicrobial properties

Daniela Benedec,1,* Ilioara Oniga,1,* Flavia Cuibus,1 Bogdan Sevastre,2 Gabriela Stiufiuc,3 Mihaela Duma,4 Daniela Hanganu,1 Cristian Iacovita,1 Rares Stiufiuc,1,5 Constantin Mihai Lucaciu1 1Faculty of Pharmacy, “Iuliu Haţieganu” University of Medicine and Pharmacy, 2Faculty of Veterinary Medicine, University of Agricultural Sciences and Veterinary Medicine, 3Faculty of Physics, “Babeş Bolyai” University, 4State Veterinary Laboratory for Animal Health and Safety, 5Department of Bionanoscopy, MedFuture Research Center for Advance Medicine, “Iuliu Haţieganu” University of Medicine and Pharmacy, Cluj-Napoca, Romania *These authors contributed equally to this work Purpose: The leaves and flowering stem of Origanum vulgare contain essential oils, flavonoids, phenolic acids and anthocyanins. We propose a new, simple, one-pot, O. vulgare extract (OVE) mediated green synthesis method of biocompatible gold nanoparticles (AuNPs) possessing improved antioxidant, antimicrobial and plasmonic properties.Materials and methods: Different concentrations of OVEs were used to reduce gold ions and to synthetize biocompatible spherical AuNPs. Their morphology and physical properties have been investigated by means of transmission electron microscopy, ultraviolet–visible absorption spectroscopy, photon correlation spectroscopy and Fourier transform infrared spectroscopy, whereas their plasmonic properties have been tested using surface-enhanced Raman spectroscopy (SERS). The antioxidant properties of nanoparticles (NPs) have been evaluated by 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay, and the antimicrobial tests were performed using the disk diffusion assay. Their cytotoxicity has been assessed by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Results: The experimental results confirmed the successful synthesis of biocompatible, spherical, plasmonic NPs having a mean diameter of ~40 nm and an outstanding aqueous stability. This new class of NPs exhibits a very good antioxidant activity and presents interesting inhibitory effects against Staphylococcus aureus and Candida albicans. Due to their plasmonic properties, AuNPs are used as SERS substrates for the detection of a test molecule (methylene blue) up to a concentration of 10-7 M and a pharmaceutical compound (propranolol) in solution. Cytotoxicity assays revealed that AuNPs are better tolerated by normal human dermal fibroblast cells, while the melanoma cancer cells are more sensitive.Conclusion: The biocompatible AuNPs synthetized using OVEs showed significant bactericidal and antimycotic activities, the most sensitive microorganisms being S. aureus and C. albicans, both commonly involved in various dermatological infections. Moreover, the significant antioxidant effect might recommend their use for protective and/or preventive effect in various skin inflammatory conditions, including the reduction in side effects in dermatological infections. Meanwhile, the as-synthesized biocompatible AuNPs can be successfully used as SERS substrates for the detection of pharmaceutical compounds in aqueous solutions. Keywords: green nanoparticles’ synthesis, toxicity, antioxidant activity, Staphylococcus aureus, Candida albicans, SER

Linewidth of resonances in scanning tunneling spectroscopy

Cryogenic scanning tunneling spectroscopy is increasingly used to study the electronic structure of adatoms, molecules, and semiconductor quantum dots. However, the width of the conductance resonances that indicate the energy levels is much larger than the thermal energy, and this is not well understood. Here, we present a comprehensive study of the line shape and width of the conductance resonances observed with small colloidal semiconductor quantum dots. Experimentally, the line shape and width are studied for CdSe quantum dots of different sizes, with nanocrystals being chemically or physically attached to the substrate. The influence of the temperature is studied from 5 K up to room temperature. We have also varied the set-point current via the tip-to-dot distance to study the effects of dissipative heating of the quantum dot. We present basic calculations of the effects of electron-phonon coupling, charge and dipole fluctuations in the close environment of the quantum dot, mechanical oscillations of the quantum dot in the tunneling junction, and internal heating by nonresonant electron transport. A comparison with the experimental results shows that electron-phonon coupling forms the main contribution to the line broadening for the lowest resonance. Fluctuations of the charge landscape around the quantum dot are most likely involved in an additional broadening. More importantly, these potential fluctuations wash out the vibronic structure of the line shape that should arise from electron-phonon coupling. Our results show that in the case of semiconductor quantum dots, internal heating due to nonresonant electron transport is not important

Transport limitations and Schottky barrier height in titanium silicide nanowires grown on the Si(111) surface

International audienc

Above-barrier surface electron resonances induced by a molecular network

We report the modification of the density of states of the Ag/Si (111)−√3×√3R30° surface by a self-assembled molecular network at energies much higher than the height of the potential barriers induced by the molecules. Map of the differential conductance obtained by scanning tunneling spectroscopy reveals an increase in the electron density in the pores of the network. This enhanced electronic resonance is explained by theoretical calculations where the periodic potential introduced by the molecular network causes band replica with an alteration of the surface band structure

Selective ex-vivo photothermal ablation of human pancreatic cancer with albumin functionalized multiwalled carbon nanotubes

Lucian Mocan1, Flaviu A Tabaran2, Teodora Mocan1, Constantin Bele3, Anamaria Ioana Orza1, Ciprian Lucan4, Rares Stiufiuc1, Ioana Manaila1, Ferencz Iulia1, Iancu Dana1, Florin Zaharie1, Gelu Osian1, Liviu Vlad1, Cornel Iancu11Department of Nanomedicine, “Iuliu Hatieganu” University of Medicine and Pharmacy, Cluj-Napoca, Romania; 2Department of Pathology, University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca, Romania; 3Department of Biochemistry, University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca, Romania; 4Clinical Institute of Urology and Renal Transplantation, Cluj-Napoca, RomaniaAbstract: The process of laser-mediated ablation of cancer cells marked with biofunctionalized carbon nanotubes is frequently called “nanophotothermolysis”. We herein present a method of selective nanophotothermolisys of pancreatic cancer (PC) using multiwalled carbon nanotubes (MWCNTs) functionalized with human serum albumin (HSA). With the purpose of testing the therapeutic value of these nanobioconjugates, we have developed an ex-vivo experimental platform. Surgically resected specimens from patients with PC were preserved in a cold medium and kept alive via intra-arterial perfusion. Additionally, the HSA-MWCNTs have been intra-arterially administered in the greater pancreatic artery under ultrasound guidance. Confocal and transmission electron microscopy combined with immunohistochemical staining have confirmed the selective accumulation of HSA-MWCNTs inside the human PC tissue. The external laser irradiation of the specimen has significantly produced extensive necrosis of the malign tissue after the intra-arterial administration of HSA-MWCNTs, without any harmful effects on the surrounding healthy parenchyma. We have obtained a selective photothermal ablation of the malign tissue based on the selective internalization of MWCNTs with HSA cargo inside the pancreatic adenocarcinoma after the ex-vivo intra-arterial perfusion.Keywords: noncovalent functionalization, irradiation, tumor, malignant, MWCNT