Single-stage in situ synthesis of silver nanoparticles in antibacterial self-assembled overlays

In this work, a novel single-stage process for in situ synthesis of Ag nanoparticles (NPs) using the layer-by-layer (LbL) technique is presented. The Ag NPs were formed into nanotextured coatings based on sequentially adsorbed poly(allylamine hydrochloride) (PAH) and SiO₂ NPs. Such highly porous surfaces have been used in the fabrication of highly efficient ion release films for applications such as antibacterial coatings. In this approach, the amino groups of the PAH acted as reducing agent and made possible the in situ formation of the Ag NPs. This reduction reaction occurred during the LbL process as the coating was assembled, without any further step after the fabrication and stabilization of the multilayer film. Biamminesilver nitrate was used as the Ag⁺ ion source during the LbL process and it was successfully reduced to Ag NPs. All coatings were tested with gram-positive and gram-negative bacterial cultures of Escherichia coli, Staphylococcus aureus, and Lactobacillus delbrueckii showing an excellent antimicrobial behavior against these types of bacteria (more than 99.9% of killing efficiency in all cases).     

Density functional theory study of the oxidation reaction in the gas and aqueous phase of allyl methyl disulfide with hydroxyl radical

Structural Chemistry - An in silico analysis of the oxidation mechanism of allyl methyl disulfide (AMDS) by hydroxyl radical was achieved at DFT level using B3LYP, CAM-B3LYP, M06-2X, and BMK...     

Optimizing nozzle convergent angle using central composite design on the particle velocity and acoustic power level for single-hose dry ice blasting nozzle

Journal of Thermal Analysis and Calorimetry - One of the important parameters in developing dry ice blasting nozzle is the high-speed dry ice pellets. However, many studies focus primarily only on...     

Use of calorimetry and thermal analysis to assess the heat of supplementary cementitious materials during the hydration of composite cementitious binders

Journal of Thermal Analysis and Calorimetry - The present paper focuses on the suitability, variability and versatility of thermal analysis and calorimetry methods in the study of cement hydration...     

Finite fuzzy cone

In this paper the concept of finite fuzzy cone is introduced.     

Laser excited time-resolved low-temperature luminescence of nucleic acid bases single crystals

The first results on low temperature (80 K) one photon fluorescence of single crystals of nucleic acids bases excited by picosecond light pulses are reported. The excitation to the first absorption band of the crystals was realized by tuning the fundamental frequency of the passive modelocked Nd:YAG laser into UV spectral region. Our spectroscopic measurements confirm previous assumptions about the excimer character of the fluorescence of the crystals. Kinetic parameters of complex fluorescence decays show a strong dependence on the exciting wavelength.     

Electrochemical characterization of fine-grained blast furnace sludge after acid leaching using carbon paste electrode

The paper deals with the study of electrochemical properties of blast furnace sludge after acid leaching (BFSL) using modified carbon paste electrodes (CPEs) in acidic (1 M HCl) and alkaline (1 M NaOH) electrolyte. A polyamide holder with exchangeable tips was developed. The effect of their geometric parameters on the electrochemical response was monitored. The electrochemical characterization was performed by cyclic voltammetry (CV) at different scan rates. The hematite and magnetite served as comparative model modifiers. The identification of reaction products was performed using the RTG diffraction and SEM/EDX analyses. It was found that reduction reactions are suppressed at acidic pH. On the contrary, in an alkaline media, a significant peak corresponding to the electrode reduction of iron oxides based on the scheme Fe³⁺?→?Fe²⁺?→?Fe⁰ was identified in the BFSL reduction region. XRD and SEM analyses of the active surface of modified CPE showed the formation of nanostructured Fe. The results provide direction for the further use of BFSL.     

Tuning of Thermoresponsivity of a Poly(2‐alkyl‐2‐oxazoline) Block Copolymer by Interaction with Surface‐Active and Chaotropic Metallacarborane Anion

Thermoresponsive nanoparticles based on the interaction of metallacarboranes, bulky chaotropic and surface‐active anions, and poly(2‐alkyl‐2‐oxazoline) block copolymers were prepared. Recently, the great potential of metallacarboranes have been recognized in biomedicine and many delivery nanosystems have been proposed. However, none of them are thermoresponsive. Therefore, a thermoresponsive block copolymer, poly(2‐methyl‐2‐oxazoline)‐block‐poly(2‐n‐propyl‐2‐oxazoline) (PMeOx–PPrOx), was synthesized to encapsulate metallacarboranes. Light scattering, NMR spectroscopy, isothermal titration calorimetry, and cryogenic TEM were used to characterize all solutions of the formed nanoparticles. The cloud‐point temperature (T_CP) of the block copolymer was observed at 30 °C and polymeric micelles formed above this temperature. Cobalt bis(dicarbollide) anion (COSAN) interacts with both polymeric segments. Depending on the COSAN concentration, this affinity influenced the phase transition of the thermoresponsive PPrOx block. The T_CP shifted to lower values at a lower COSAN content. At higher COSAN concentrations, the hybrid nanoparticles are fragmented into relatively small pieces. This system is also thermoresponsive, whereby an increase in temperature leads to higher polymer mobility and COSAN release.     

Theoretical calculations of refractive indices and optical effects in spectra of nitric acid and nitric acid monohydrate crystals

The theoretical infrared refractive indices of two systems related to atmospheric research, nitric acid (NA) and nitric acid monohydrate (NAM) crystals, have been computed using a methodology based on first-principles. The effects of lack of coherence in the infrared beam in RAIR and transmission spectra have also been treated using a model based on classical optics. The optical constants of NA crystals are presented for the first time; the results on NAM are compared to empirical values previously published with good general agreement. With the optical constants of NA, polarized reflection-absorption infrared spectra are predicted and compared to experimental spectra recorded also for the first time, for a set of varying film thickness. The global agreement is satisfactory. The effects of a number of experimental factors in transmission spectra of NAM are assessed, in an attempt to explain observed differences among experimental spectra. It is concluded that the spectral disparities are probably due to differences in the nature of the samples.