Marija Radoičić

Sonophotocatalytic degradation of dye C.I. Acid Orange 7 by TiO2 and Ag nanoparticles immobilized on corona pretreated polypropylene non-woven fabric.

This study discusses the possibility of using corona pre-treated polypropylene (PP) non-woven fabric as a support for immobilization of colloidal TiO2 and Ag nanoparticles in order to remove dye C.I. Acid Orange 7 from aqueous solution. Dye removal efficiency by sonocatalysis, photocatalysis and sonophotocatalysis was evaluated on corona pre-treated fabric loaded with TiO2 nanoparticles, corona pre-treated fabric double loaded with TiO2 nanoparticles and corona pre-treated fabrics loaded with TiO2 nanoparticles before and after deposition of Ag nanoparticles. In addition, the stability of PP non-woven fabric during these processes was investigated. The substrates were characterized by SEM, EDX and AAS analyses. The change of the dye concentration was evaluated by UV-VIS spectrophotometry. Unlike sonocatalysis and photocatalysis, complete dye removal from both solution and non-woven fabric was obtained already after 240-270 min of sonophotocatalysis. Corona pre-treated PP non-woven fabric loaded with Ag nanoparticles prior to deposition of TiO2 nanoparticles provided excellent degradation efficiency and superior reusability. Sonophotocatalytic degradation of dye in the presence of all investigated samples was the most prominent in acidic conditions. Although this nanocomposite system ensured fast discoloration of dye solution, TOC values of water measured after sonophotocatalysis were not satisfactory because of PP degradation. Therefore, it is suggested to include TOC evaluation in each case study where different supports for TiO2 nanoparticles are used since these nanoparticles may guarantee the dye removal from solution but the stability of support could be problematic causing even more serious environmental impact.

In situ photoreduction of Ag+-ions by TiO2 nanoparticles deposited on cotton and cotton/PET fabrics

The possibility of in situ photoreduction of Ag+-ions using TiO2 nanoparticles deposited on cotton and cotton/PET fabrics in the presence of amino acid alanine and methyl alcohol has been discussed. The possible interaction between TiO2, alanine and Ag+-ions was evaluated by FTIR analysis. The fabrication of TiO2/Ag nanoparticles on both fabrics was confirmed by SEM, EDX, XRD, XPS and AAS analyses. Cotton and cotton/PET fabrics impregnated with TiO2/Ag nanoparticles provided maximum reduction of Gram-negative bacteria Escherichiacoli and Gram-positive bacteria Staphylococcusaureus. Although excellent antibacterial activity was preserved after ten washing cycles, a significant amount of silver leached out from the fabrics into the washing bath. The perspiration fastness assessment revealed that smaller amounts of silver were also released from the fabrics into artificial sweat at pH 5.50 and 8.00. In addition, deposited TiO2/Ag nanoparticles imparted maximum UV protection to fabrics.

Colloidal TiO2 nanoparticles as substrates for M(S)ALDI mass spectrometry of transition metal complexes

RATIONALE Nanoparticles as substrates for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) have advantages over organic matrices, since they enable acquisition of spectra in the low-mass range. It has been previously shown that TiO(2) nanoparticles can be used as substrate for MALDI-TOF MS analysis of phospholipids and for other types of molecules, but none of them was applied to the analysis of transition metal complexes. METHODS The MALDI-TOF mass spectra of potential anti-tumor drugs [AuCl(2)(bipy)]Cl, [PtCl(4)(bipy)], and [RuCl(2)(bipy)(2) ]Cl acquired with organic matrices have been compared with spectra acquired with colloidal titanium dioxide nanoparticles. Colloidal TiO(2) nanoparticles (NPs) with average diameter of 5 nm were synthesized and characterized by microscopy. For some experiments, the TiO(2) NPs were treated at 60 °C. Suspensions of matrix and the analyte were premixed, applied to the MALDI target and left at room temperature. Mass spectra were acquired with a 50-Hz pulsed nitrogen laser emitting at a wavelength of 337 nm. RESULTS The MALDI spectra of transition metal complexes acquired with TiO(2) NPs exhibited somewhat lower sensitivity than those with organic matrices; on the other hand, they are characterized by significantly lower number of signals arising from the tested complexes than the organic matrices. Whereas adducts between organic matrices and the analytes were detectable in the spectra, this was not the case for the TiO(2)-assisted mass spectra. CONCLUSIONS We have shown that colloidal TiO(2) NPs can be used as substrates for MALDI-TOF MS of transition metal complexes. Although the sensitivity of this approach in comparison with the use of organic matrices might still be a problem, the potential of the applications of NPs for the mass spectrometric characterization of transition metal complexes is clearly demonstrated.

Negative influence of Ag and TiO2 nanoparticles on biodegradation of cotton fabrics

Abstract Recently, many efforts have been made to efficiently impregnate different textile materials with metal and metal oxide nanoparticles in order to provide antimicrobial, UV protective or self-cleaning properties. Evidence of their environmental risks is limited at this point. The aim of this study was to explore the influence of Ag and TiO2 nanoparticles on biodegradation of cotton fabrics. Biodegradation behavior of cotton fabrics impregnated with Ag and TiO2 NPs from colloidal solutions of different concentrations was assessed according to standard test method ASTM 5988-03 and soil burial test. Degradation of cotton fabrics was also evaluated by enzymatic hydrolysis with cellulase. The morphology of fibers affected by biodegradation was analyzed by scanning electron microscopy (SEM). In order to get better insight into biodegradation process, dehydrogenase activity of soil has been determined. Ag and particularly TiO2 nanoparticles suppressed the biodegradation of cotton fabrics. The dehydrogenase activity of soil with cotton fabrics impregnated with TiO2 nanoparticles was the weakest. Severe damage of cotton fibers during the biodegradation process was confirmed by SEM.Graphical Abstract

Biodegradation of cotton and cotton/polyester fabrics impregnated with Ag/TiO2 nanoparticles in soil

This study discusses the biodegradation behavior of cotton and cotton/PET fabrics impregnated with Ag/TiO2 nanoparticles in soil. Biodegradation behavior was evaluated by standard test method ASTM 5988-03 based on determination of percentage conversions of carbon content to CO2 as well as by soil burial test and enzymatic hydrolysis with cellulase where the extent of biodegradation was estimated by the calculation of fabric weight loss. The morphological and chemical changes of fibers during biodegradation process were analyzed by SEM and FTIR spectroscopy, respectively. The results obtained by all applied methods suggested that Ag/TiO2 nanoparticles hindered the biodegradation of investigated cotton and cotton/PET fabrics. Soil burial test indicated faster biodegradation of the impregnated blend compared to impregnated cotton fabric which is attributed to smaller amount of fabricated Ag nanoparticles on the blend proved by AAS measurement. Similar trend was established by enzymatic hydrolysis of cotton fibers. Severe damage of cotton fibers in both fabrics due to biodegradation process was confirmed by SEM. However, the cotton fiber damage occurred to a lesser extent in the samples that were impregnated with Ag/TiO2 nanoparticles. PET fibers remained intact which was also indicated by FTIR analysis.

In situ photoreduction of Ag + -ions on the surface of titania nanotubes deposited on cotton and cotton/PET fabrics

This study discusses the possibility of in situ photoreduction of Ag+-ions on the surface of titania nanotubes (TNTs) deposited on the cotton and cotton/PET fabrics in the presence of amino acid alanine and methyl alcohol. TNTs were synthetized by hydrothermal method. The proposed interaction between titania, alanine and Ag+-ions was based on the results obtained by FTIR measurements. In order to enhance the binding efficiency between TNTs and fibers, the fabrics were previously impregnated with polyethyleneimine. The presence of TNT/Ag nanocrystals on the surface of fibers was proved by SEM, AAS, XRD and XPS. Larger amount of silver was detected on the cotton fabric. Fabricated TiO2/Ag nanocrystals provided maximum reduction of bacteria E. coli which was preserved after five washing cycles despite significant release of silver. The perspiration fastness tests indicated that silver release did not depend on pH. The presence of TNT/Ag nanocrystals imparted maximum UV protection to fabrics.

Improvement of Dye Solar Cell Efficiency by Photoanode Posttreatment

The basic concept for efficiency improvement in dye-sensitized solar cells (DSSC) is limiting the electron-hole recombination. One way to approach the problem is to improve the photogenerated charge carriers lifetime and consequently reduce their recombination probability. We are reporting on a facile posttreatment of the mesoporous photoanode by using a colloidal solution of TiO2 nanoparticles. We have investigated the outcome of the different sintering temperature of the posttreated photoanodes on their morphology as well as on the conversion efficiency of the DSSC. The DSSCs composed of posttreated photoanodes at 450°C showed an increase in and consequently an increase in efficiency of 10%. Investigations were made to determine the electron recombination via the electrolyte by the OCVD technique. We found that the posttreatment has the effect of reducing the surface trap states and thus increases the electron lifetime, which is responsible for the increase of the overall cell efficiency.

Photocatalytic decomposition of selected biologically active compounds in environmental waters using TiO2/polyaniline nanocomposites: Kinetics, toxicity and intermediates assessment

A comprehensive study of the removal of selected biologically active compounds (pharmaceuticals and pesticides) from different water types was conducted using bare TiO2 nanoparticles and TiO2/polyaniline (TP-50, TP-100, and TP-150) nanocomposite powders. In order to investigate how molecular structure of the substrate influences the rate of its removal, we compared degradation efficiency of the initial substrates and degree of mineralization for the active components of pharmaceuticals (propranolol, and amitriptyline) and pesticides (sulcotrione, and clomazone) in double distilled (DDW) and environmental waters. The results indicate that the efficiency of photocatalytic degradation of propranolol and amitriptyline was higher in environmental waters: rivers (Danube, Tisa, and Begej) and lakes (Moharač, and Sot) in comparison with DDW. On the contrary, degradation efficacy of sulcotrione and clomazone was lower in environmental waters. Further, of the all catalysts applied, bare TiO2 and TP-100 were found to be most effective in the mineralization of propranolol and amitriptyline, respectively, while TP-150 appeared to be the most efficient in terms of sulcotrione and clomazone mineralization. Also, there was no significant toxicity observed after the irradiation of pharmaceuticals or pesticides solutions using appropriate catalysts on rat hepatoma (H-4-II-E), mouse neuroblastoma (Neuro-2a), human colon adenocarcinoma (HT-29), and human fetal lung (MRC-5) cell lines. Subsequently, detection and identification of the formed intermediates in the case of sulcotrione photocatalytic degradation using bare TiO2 and TP-150 showed slightly different pathways of degradation. Furthermore, tentative pathways of sulcotrione photocatalytic degradation were proposed and discussed.

Antibacterial activity of Cu-based nanoparticles synthesized on the cotton fabrics modified with polycarboxylic acids

The fabrication of antimicrobial textile nanocomposite by in situ synthesis of Cu-based nanoparticles on cotton fabrics modified with different polycarboxylic acids was discussed in this study. In order to evaluate the influence of carboxyl group content on Cu2+-ions adsorption, their subsequent reduction with sodium borohydride and formation of Cu-based nanoparticles, cotton fabrics were modified with succinic, citric and 1,2,3,4-butanetetracarboxylic acids. It was shown that the larger the number of carboxyl groups in applied acid, the larger the content of free carboxyl groups on the fibers and consequently, the larger the Cu2+-ions uptake and total amounts of Cu-based nanoparticles. On the basis of the XPS and XRD measurements, it was suggested that synthesized nanoparticles were mixture of Cu2O and CuO. Fabricated nanocomposites provided maximum reduction of Gram-negative bacterium E. coli and Gram-positive bacterium S. aureus and controlled release of Cu2+-ions in physiological saline solution which are necessary prerequisites for infection prevention.