Porous Silicon Preparation by Electrochemical Etching in Ionic Liquids

International audienceAnodic etching of n-type {111} silicon in ionic liquid (IL) systems ([RMIM] [X], R = H, Bu; X = BF4-, PF6-), realized under galvanostatic conditions and at room temperature, allowed the formation of porous silicon surfaces with different pore morphology depending on the etching time, current density, and the IL used. The study of the effect of water content in IL on the etching process has shown a water content of 1% to be optimal. The role of the anion on the etching process was elucidated using 1-methylimidazolium tetrafluoroborate ([HMIM][BF4]) and 1-methylimidazolium hexafluorophosphate ([HMIM] [PF6]) IL systems. [HMIM] [BF4] was found to be most efficient for the formation of a silicon nanostructured array with a pore size of 30-80 nm. The thusprepared porous silicon samples show fluorescence in blue light (475 nm). The NMR spectra of [HMIM] [BF4] ionic liquid before and after etching do not show noticeable changes, which makes it possible to consider this IL as a potentially recyclable etching agent

Natural Nanoclay-Based Silver-Phosphomolybdic Acid Composite with a Dual Antimicrobial Effect

[Image: see text] The problem of microbial growth on various surfaces has increased concern in society in the context of antibiotic misuse and the spreading of hospital infections. Thus, the development of new, antibiotic-free antibacterial strategies is required to combat bacteria resistant to usual antibiotic treatments. This work reports a new method for producing an antibiotic-free antibacterial halloysite-based nanocomposite with silver nanoparticles and phosphomolybdic acid as biocides, which can be used as components of smart antimicrobial coatings. The composite was characterized by using energy-dispersive X-ray fluorescence spectroscopy and transmission electron microscopy. The release of phosphomolybdic acid from the nanocomposite was studied by using UV–vis spectroscopy. It was shown that the antibiotic-free nanocomposite consisting of halloysite nanotubes decorated with silver nanoparticles loaded with phosphomolybdic acid and treated with calcium chloride possesses broad antibacterial properties, including the complete growth inhibition of Staphylococcus aureus and Pseudomonas aeruginosa bacteria at a 0.5 g × L(–1) concentration and Acinetobacter baumannii at a 0.25 g × L(–1) concentration

Halloysite Nanotubes with Immobilized Plasmonic Nanoparticles for Biophotonic Applications

Halloysite nanotubes (HNTs) with immobilized gold (Au) and silver (Ag) nanoparticles (NPs) belong to a class of nanocomposite materials whose physical properties and applications depend on the geometry of arrangements of the plasmonic nanoparticles on HNT’ surfaces. We explore HNTs:(Au, Ag)-NPs as potential nano-templates for surface-enhanced Raman scattering (SERS). The structure and plasmonic properties of nanocomposites based on HNTs and Au- and Ag-NPs are studied by means of the transmission electron microscopy and optical spectroscopy. The optical extinction spectra of aqueous suspensions of HNTs:(Au, Ag)-NPs and spatial distributions of the electric fields are simulated, and the simulation results demonstrate the corresponding localized plasmonic resonances and numerous “hot spots” of the electric field nearby those NPs. In vitro experiments reveal an enhancement of the protein SERS in fibroblast cells with added HNTs:Ag-NPs. The observed optical properties and SERS activity of the nanocomposites based on HNTs and plasmonic NPs are promising for their applications in biosensorics and biophotonics

Table_1_Epinephrine extensively changes the biofilm matrix composition in Micrococcus luteus C01 isolated from human skin.DOCX

The importance of the impact of human hormones on commensal microbiota and microbial biofilms is established in lots of studies. In the present investigation, we continued and extended the research of epinephrine effects on the skin commensal Micrococcus luteus C01 and its biofilms, and also the matrix changes during the biofilm growth. Epinephrine in concentration 4.9 × 10–9 M which is close to normal blood plasma level increased the amount of polysaccharides and extracellular DNA in the matrix, changed extensively its protein, lipid and polysaccharide composition. The Ef-Tu factor was one of the most abundant proteins in the matrix and its amount increased in the presence of the hormone. One of the glucose-mannose polysaccharide was absent in the matrix in presence of epinephrine after 24 h of incubation. The matrix phospholipids were also eradicated by the addition of the hormone. Hence, epinephrine has a great impact on the M. luteus biofilms and their matrix composition, and this fact opens wide perspectives for the future research.</p

Data_Sheet_1_Epinephrine extensively changes the biofilm matrix composition in Micrococcus luteus C01 isolated from human skin.DOCX

The importance of the impact of human hormones on commensal microbiota and microbial biofilms is established in lots of studies. In the present investigation, we continued and extended the research of epinephrine effects on the skin commensal Micrococcus luteus C01 and its biofilms, and also the matrix changes during the biofilm growth. Epinephrine in concentration 4.9 × 10–9 M which is close to normal blood plasma level increased the amount of polysaccharides and extracellular DNA in the matrix, changed extensively its protein, lipid and polysaccharide composition. The Ef-Tu factor was one of the most abundant proteins in the matrix and its amount increased in the presence of the hormone. One of the glucose-mannose polysaccharide was absent in the matrix in presence of epinephrine after 24 h of incubation. The matrix phospholipids were also eradicated by the addition of the hormone. Hence, epinephrine has a great impact on the M. luteus biofilms and their matrix composition, and this fact opens wide perspectives for the future research.</p