Transition dynamics from optical saturable absorption (SA) to reverse saturable absorption (RSA) in multi-walled carbon nanotube (MWCNT)-doped fast sol-gel hybrid organic/inorganic glasses was studied by optical transmission of 532 nm laser pulses. Exposure to 6 ns long, temporally isolated single pulses of energies between 10(-3) and 2 x 10(-2) J/cm(2) exhibited SA. Exposure to 1.5 ns long, 11 kHz repetitive pulses of energies between 2 x 10(-2) and 1 J/cm(2) exhibited a gradual development of RSA at a rate that increases with the pulse energy. SA results were analyzed by the slow saturable absorber theory, yielding a ground-state absorption cross section sigma(gs) = (1.5 +/- 0.1) x 10(-14) cm(2) for a (2.0 +/- 0.13) x 10(15) cm(-3) density of states. The first excited state absorption cross section was sigma(es1) = (9.3 +/- 0.6) x 10(-16) cm(2) for a much higher, (2.3 +/- 0.15) x 10(16) cm(-3), density of states. The SA/RSA transition temporal evolution effects were modeled by a five-level energy scheme. The numerical simulation yielded light-intensity dependent parameters: ground-state densities decreasing from (9 +/- 0.5) x 10(22) to (2 +/- 0.1) x 10(21) cm(-3); ground-state absorption cross sections increasing from (2 +/- 0.1) x 10(-22) to (9.0 +/- 0.5) x 10(-21) cm(2); and excited state absorption cross sections increasing from (7.8 +/- 0.4) x 10(-22) to ( 3.3 +/- 0.15) x 10(-20) cm(2). The occurrence of such huge state densities is consistent with observation by others on the formation of ionized carbon-black particles as plasma states under illumination. (C) 2015 Optical Society of America

The properties of non-linear inorganic chalcogenide photoresists fabricated by co-evaporation of Ag with amorphous arsenic sulfide-selenide materials are considered in detail. The influence of several factors, including Ag concentration, irradiation wavelength and composition of the developer on the photoresists characteristics was studied. Superlinear dissolution characteristics of the photoresists are explained in the frame of the so-called “percolation approach”. The advantages of superlinear photoresists, especially for the case of maskless photolithography, are briefly discussed.

Inorganic chalcogenide photoresists are widely used in microelectronics and optoelectronics. Here, we describe strongly nonlinear chalcogenide photoresists fabricated on the basis of Ag-doped As2S3 glassy films. Photoresists are prepared by vacuum coevaporation of As2S3 bulk glass and Ag. Superlinear dissolution characteristics of Ag-doped photoresists are explained in the framework of the so-called “percolation approach.” The advantages of superlinear photoresists for maskless photolithography are briefly discussed.

In glassy Ge28.5Pb15S56.5 films, we observed and studied the phenomenon of transient photorefraction-a change in refractive index during light irradiation, which is not accompanied by metastable photodarkening. Some possibilities for the explanation of this phenomenon are pointed out, and this phenomenon is claimed to be typical of films of many chalcogenide glassy semiconductors.

Silver metal evaporated below or above a layer of As(2)S(3) glass are known to propagate under action of light within the glass layer and strongly modify its photochemical properties. We demonstrate that when silver is co-evaporated together with the glass, and within a certain range of silver concentration. this property is conserved locally. This leads to a new kind of photosensitive effect in the chalcogenide glass with completely new photoresist properties such as giant contrast and superlinear dissolution. These new properties make silver doped As(2)S(3) glass an ideal material for the fabrication of three-dimensional structures with sub-micron feature size. The effect is explained within a percolation model. The advantages of superlinear photoresists, especially for the case of maskless photolithography, are shortly discussed

We use the fast marching algorithm to simulate the process of the lithographic development (chemical etching) taking a major part in the procedure of the holographic lithography fabrication of photonic crystals. We also develop a method for the check of the bi-continuity of the resulting crystals. The technique furthermore allows removing of the disconnected regions. The simulation turns out to be particularly important for the newly used chalcogenide glasses. The comparison between the simulation and the experiment shows an excellent agreement.

We have developed a three-dimensional simulation algorithm based on fast marching method that mimics the etching behavior of chalcogenide photoresists, especially for maskless interference lithography. This lithography exposure is characterized by continuous variation of the exposure intensity inside the photoresist, without step like variation. Furthermore, the chalcogenide photoresist has a "gray-scale" behavior, without definite threshold. The resulting etching process is very sensitive to exposure dose and etching time. The optimal relations between these parameters are determined both theoretically and experimentally. A very good agreement between calculation and experimental results is shown, opening the door to complex nanostructures engineering.

Photoinduced phenomena, such as photodarkening, photorefraction, and photodissolution, were studied in different compositions of three-component mAs2S3·nAs2Se3 amorphous films. The main emphasis was on the effect of photoinduced change of dissolution rate since this effect is the basis of many applications of amorphous chalcogenide films. The results of the investigation were compared with photoinduced effects in binary As2S3 and As2Se3 films. Advanced micro-optical devices: micro-lens and micro-mirror arrays, diffractive gratings, and photonic bandgap crystals, based on three-component amorphous films which possessed optimal photodissolution characteristics were developed. The primary parameters of the micro-optical devices developed are discussed.

Thin films fabricated by coevaporation in vacuum of chalcogenide glass and a rare-earth (RE) containing material are shown to have strong rare-earth photoluminescence, photostructural transformations and photoinduced anisotropy. The photoluminescence spectra of the films are similar to that of very different Nd- and Er-doped solids. Effects of concentration quenching of luminescence and luminescence fatigue are observed and studied. Using the photoresist effect of the doped films, binary diffraction gratings possessing strong IR photoluminescence were prepared.

Nanocrystalline particles of MgO were synthesized using microwave radiation in an ethylene glycol solution. The antibacterial activities of the MgO nanoparticles were tested by treating Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures with 1 mg mL(-1) of the nanoparticles. We have examined the importance of the size effect, pH, and the form of the active MgO species as a bactericidal agent. A clear size dependence of the nanoparticles is observed where the amount of eradicated bacteria was strongly dependent on the particle size.

Arsenic based chalcogenide glasses present several advantages for nano-structured optical devices in the infrared. First they possess a good transparency in this optical window, second their amorphous nature is ideal for coating based applications or for hybrid integration, third their photo-structural transformation properties give the possibility of creating high-resolution patterns on films and finally their high index make them particularly suitable for the fabrication of photonic crystal devices. We have demonstrated the fabrication of two-dimensional and three-dimensional (wood-pile) photonic crystal structures for typically 500 nm period structures using interferometric lithography to create the periodic pattern. We show here different techniques in order to obtain specific patterns on the chalcogenide glass using a combination of illumination, etching and redeposition techniques. Moreover, in order to create very steep contrast, we have used the fact that silver ions can freely propagate in the glass under light action, providing a very effective contrast between illuminated and non-illuminated regions. 130 nm patterns with a 500 nm periodicity have been obtained using silver doping of chalcogenide glasses. We will finally show different examples of pattern sculpturing using different illumination and film preparation conditions.

A one-step sonochemical process starting with the native BSA and tetracycline was employed to encapsulate the antibiotic drug in microspheres of BSA. The tetracycline loading studies showed that the maximum tetracycline loading capacity was found to be 65%. The antimicrobial activity of the tetracycline loaded in BSA microspheres was demonstrated on two bacterial strains that are sensitive to tetracycline.

The occurrence of Vibrio vulnificus incoastal sea water and sand was investigated. Samples (286 in toto) were taken during the period between November 1993 and July 1994. Ten V. vulnificus isolates (6.9%) were recovered from sea water and two isolates were recovered from sand (1.4%). The total isolation rate for this period was 4.2%. In a longer period of investigation, from June 1996 until June 1998 (24 months), 1,248 samples were taken and 205 V. vulnificus isolates were recorded (32.8%) in sea water while only 18 isolates in sand (2.9%). The total isolation rate was 17.9%. The monthly occurrence of this bacterial species in the various beaches surveyed demonstrated that V. vulnificus is more frequent during the months of July, August and September. The increase in the number of isolates during the past 2 years started as early as March and finished as late as October. Antibiotic sensitivity testing revealed that this species is sensitive to most antibiotics, except polymyxin B and colistin. The relatively high isolation rate of this bacterium from sea water may be dangerous to bathers, fishermen and divers with predisposed wounds.

Abstract— The antibacterial photodynamic effects of uncharged (o‐tetrahydroxyphenyl porphine [THPP], m‐THPP and p‐THPP), cationic (5,10,15,20‐tetra[4‐N‐methylpyridyllporphine [TMPyP]) and anionic (5,10,15,20‐tetra[4‐sulfonatophenyl porphine] [TPPS4]) porphines on Staphylococcus aureus and Escherichia coli bacteria inactivation were examined. The results show that uncharged porphines provoked antibacterial photodynamic activity on S. aureus, and also on E. coli in the presence of the membrane‐disorganizing peptide polymixin B nonapeptide (PMNP). The TMPyP compound was highly photoactive toward gram‐positive bacteria but only marginally effective on gram‐negative cells, whereas TPPS4 showed no activity on either gram‐positive or gram‐negative bacteria. The photoactivity of TMPyP is due to the electrostatic attraction between the positively charged sensitizer molecule and the negatively charged membrane of the gram‐positive target cells. For TPPS4, the inactivity toward gram‐positive bacteria is due to electrostatic repulsion between the charged sensitizer molecule and the cell membrane. For gram‐negative bacteria, the inactivity is conceivably due to preferential (electrostatic) binding to the positively charged PMNP, which is an adjuvant for membrane disorganization, but has no effect on cell viability. For hydrophobic sensitizers, the photoactivity depends on the state of aggregation. The extent of deaggregation of the different THPP isomers was determined by fluorescence measurements of bound sensitizers and could be positively correlated with their photoinactivation capacity. We conclude that the structure‐activity relationships of these porphines are affected by their net charge and by aggregation.