Indigo carmine is a commonly used industrial blue dye. To determine its concentration in a commercially available food dye composed of a mixture of indigo carmine and D-glucose, this paper ...characterizes it through (ATR, KBr) FTIR micro-Raman as well as UV/Vis and clock: Briggs–Rauscher (BR) oscillatory reaction methods. The indigo carmine was detected in the bulk food dye only by applying micro-Raman spectroscopy, indicating a low percentage of the indigo carmine present. This research provides an improvement in the deviations from the experimental Raman spectrum as calculated by the B97D/cc-pVTZ level of theory one, resulting in a better geometrical optimization of the indigo carmine molecule compared to data within the literature. The analytical curves used to determine indigo carmine concentrations (and quantities) in an aqueous solution of food dye were applied by means of UV/Vis and BR methods. BR yielded significantly better analytical parameters: 100 times lower LOD and LOQ compared to commonly used UV/Vis. The remarkable sensitivity of the BR reaction towards indigo carmine suggests that not only does indigo carmine react in an oscillatory reaction but also its decomposition products, meaning that the multiple oxidation reactions have an important role in the BR’s indigo carmine mechanism. The novelty of this research is the investigation of indigo carmine using a clock BR reaction, opening new possibilities to determine indigo carmine in other complex samples (pharmaceutical, food, etc.).
ZnO nanopowders were produced using microwave processing of a precipitate and applied as a photoanode for photoelectrochemical water splitting. Two different surfactants, cetyltrimethylammonium ...bromide (CTAB) as the cationic and Pluronic F127 as the non-ionic one, were employed to
in situ
adjust the surface-to-bulk defect ratio in the ZnO crystal structure and further to modify the photo(electro)catalytic activity of the ZnO photoanode. The crystal structure, morphological, textural, optical and photo(electro)catalytic properties of ZnO particles were studied in detail to explain the profound effects of the surfactants on the photoanode activity. The ZnO/CTAB photoanode displayed the highest photocurrent density of 27 mA g
−1
, compared to ZnO (10.4 mA g
−1
) and ZnO/F127 photoanodes (20 mA g
−1
) at 1.5 V
vs.
SCE in 0.1 M Na
2
SO
4
under visible illumination of 90 mW cm
−2
. A significant shift of the overpotential toward lower values was also observed when photoanodes were illuminated. The highest shift of the overpotential, from 1.296 to 0.248 V
vs.
SCE, was recorded when the ZnO/CTAB photanode was illuminated. The ZnO/CTAB photoanode provides efficient charge transfer across the electrode/electrolyte interface, with a longer lifetime of photogenerated electron-hole pairs and reduced possibility of charge recombination. The photoconversion efficiency was improved from 1.4% for ZnO and 0.9% for ZnO/F127 to 4.2% for ZnO/CTAB at 0.510 mV. A simple procedure for the synthesis of ZnO particles with improved photo(electro)catalytic properties was established and it was found that even a small amount of CTAB used during processing of ZnO increases the surface-to-bulk defect ratio. Optimization of the surface-to-bulk defect ratio in ZnO materials enables increase of the absorption capacity for visible light, rendering of the recombination rate of the photogenerated pair, as well as increase of both the photocurrent density and photoconversion efficiency.
Employing CTAB in the microwave synthesis of ZnO particles enables improvement of their visible light absorption capacity and photo(electro)catalytic activity.
Structural modification of different carbon-based nanomaterials is often necessary to improve their morphology and optical properties, particularly the incorporation of N-atoms in graphene quantum ...dots (GQDs). Here, a clean, simple, one-step, and eco-friendly method for N-doping of GQDs using gamma irradiation is reported. GQDs were irradiated in the presence of the different ethylenediamine (EDA) amounts (1 g, 5 g, and 10 g) and the highest % of N was detected in the presence of 10 g. N-doped GQDs emitted strong, blue photoluminescence (PL). Photoluminescence quantum yield was increased from 1.45, as obtained for non-irradiated dots, to 7.24% for those irradiated in the presence of 1 g of EDA. Modified GQDs were investigated as a PL probe for the detection of insecticide Carbofuran (2,2-Dimethyl-2,3-dihydro-1-benzofuran-7-yl methylcarbamate) and herbicide Amitrole (3-amino-1,2,4-triazole). The limit of detection was 5.4 μmol L−1 for Carbofuran. For the first time, Amitrole was detected by GQDs in a turn-off/turn-on mechanism using Pd(II) ions as a quenching agent. First, Pd(II) ions were quenched (turn-off) PL of GQDs, while after Amitrole addition, PL was recovered linearly with Amitrole concentration (turn-on). LOD was 2.03 μmol L−1. These results suggest that modified GQDs can be used as an efficient new material for Carbofuran and Amitrole detection. Furthermore, the phototoxicity of dots was investigated on both Gram-positive and Gram-negative bacterial strains. When bacterial cells were exposed to different GQD concentrations and illuminated with light of 470 nm wavelength, the toxic effects were not observed.
Nowadays, it is a great challenge to develop new medicines for treating various infectious diseases. The treatment of these diseases is of utmost interest to further prevent the development of ...multi-drug resistance in different pathogens. Carbon quantum dots, as a new member of the carbon nanomaterials family, can potentially be used as a highly promising visible-light-triggered antibacterial agent. In this work, the results of antibacterial and cytotoxic activities of gamma-ray-irradiated carbon quantum dots are presented. Carbon quantum dots (CQDs) were synthesized from citric acid by a pyrolysis procedure and irradiated by gamma rays at different doses (25, 50, 100 and 200 kGy). Structure, chemical composition and optical properties were investigated by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, UV-Vis spectrometry and photoluminescence. Structural analysis showed that CQDs have a spherical-like shape and dose-dependent average diameters and heights. Antibacterial tests showed that all irradiated dots had antibacterial activity but CQDs irradiated with dose of 100 kGy had antibacterial activity against all seven pathogen-reference bacterial strains. Gamma-ray-modified CQDs did not show any cytotoxicity toward human fetal-originated MRC-5 cells. Moreover, fluorescence microscopy showed excellent cellular uptake of CQDs irradiated with doses of 25 and 200 kGy into MRC-5 cells.
The in vitro influence of Keggin structure polyoxotungstates, 12-tungstosilicic acid, H4SiW12O40 (WSiA) and 12-tungstophosphoric acid, H3PW12O40 (WPA), and monomer Na2WO4×2H2O on rat synaptic plasma ...membrane (SPM) Na+/K+-ATPase and E-NTPDase activity was studied, whereas the commercial porcine cerebral cortex Na+/K+-ATPase served as a reference. Dose-dependent Na+/K+-ATPase inhibition was obtained for all investigated compounds. Calculated IC50 (10min) values, in mol/l, for SPM/commercial Na+/K+-ATPase, were: 3.4×10−6/4.3×10−6, 2.9×10−6/3.1×10−6 and 1.3×10−3/1.5×10−3 for WSiA, WPA and Na2WO4×2H2O, respectively. In the case of E-NTPDase, increasing concentrations of WSiA and WPA induced its activity reduction, while Na2WO4×2H2O did not noticeably affect the enzyme activity at all investigated concentrations (up to 1×10−3mol/l). IC50 (10min) values, obtained from the inhibition curves, were (in mol/l): 4.1×10−6 for WSiA and 1.6×10−6 for WPA. Monolacunary Keggin anion was found as the main active molecular species present under physiological conditions (in the enzyme assays, pH 7.4), for the both polyoxotungstates solutions (1mmol/l), using Fourier transform infrared (FT-IR) and micro-Raman spectroscopy. Additionally, commercial porcine cerebral cortex Na+/K+-ATPase was exposed to the mixture of Na2WO4×2H2O and WSiA at different concentrations. Additive inhibition effect was achieved for lower concentrations of Na2WO4×2H2O/WSiA (⩽1×10−3/4×10−6 mol/l), while antagonistic effect was obtained for all higher concentrations of the inhibitors.
Objective
To measure degree of conversion (DC) of a flowable composite, microtensile bond strength (MTBS) to dentine in the snow‐plow technique with/without preheating and temperature in the ...preheated composite.
Materials and Methods
For DC, snow‐plow specimens of Filtek Ultimate Flowable (Flow) and Filtek Bulk Fill (Bulk) (3M) were prepared by light‐curing composites simultaneously in standardized molds while in control groups light‐curing was separate. DC of Flow was measured using micro‐Raman spectroscopy. For MTBS, specimens were prepared on dentine of human extracted molars by simultaneous (snow‐plow) or separate (control) light‐curing. MTBS was measured using a universal testing machine after 24 h and 6 months. Data were analyzed using ANOVA with Tukey's post hoc (α = 0.05).
Results
Increased curing time significantly increased DC in snow‐plow from 13.4% ± 11.6% (10 s) to 31.8% ± 4.4% (40 s) albeit significantly lower than controls (p < 0.05). Preheated Bulk improved conversion in snow‐plow (44.3% ± 1.7%) and control (50.5% ± 2.6%) (p < 0.05). No significant differences occurred in MTBS between groups (p > 0.05). MTBS values ranged between 66.7 ± 8.4 MPa (snow‐plow group_21°C_baseline) and 54.1 ± 15.8 MPa (control_21°C_long‐term). Temperature in the preheated Bulk dropped to ~38°C after 30 s.
Conclusions
Snow‐plow technique, irrespective of preheating, resulted in lower DC of Flow than separate light‐curing of composite increments. Snow‐plow, irrespective of preheating, resulted in similar initial and long‐term MTBS to dentine.
Clinical Significance
Clinicians with preference for flowable composite liners in Class II restorations should be aware that the snow‐plow technique of simultaneous light‐curing of flowable and bulk‐fill composite increments affects monomer‐to‐polymer conversion, albeit no effect on immediate, and long‐term bonding to dentine was detected. Preheating sculptable bulk‐fill composite improves conversion of the flowable liner in the snow‐plow technique but has no detectable effect on bond strength to dentine.
Ion beam irradiation is a versatile tool for structural modification and engineering of new materials. In this study, 12‐tungstophosphoric acid (WPA) films of different thickness were spin‐coated on ...platinized silicon substrate and irradiated with low energy hydrogen ions (10 keV) and swift heavy ions (Bi, Xe, and V) with energies up to 710 MeV. The different energy/fluence combinations allowed controllable structural changes that were investigated in detail using Raman and Infrared spectroscopy. For 120‐nm‐thick WPA samples, the irradiation led to the decrease of intensity of the skeletal and W‐Oc‐W bands of Keggin anion in order: Bi < V < Xe (for their applied energy/fluence combination). Also, symmetry change of Keggin anion similar to the one observed in the case of Keggin anions interacting with the supports was observed. For the selected ion beam irradiation parameters, xenon ion beam induced transformation of WPA to polytungstate. For 20‐μm‐thick WPA samples, the irradiation with hydrogen ion beam induced changes of skeletal vibrations and increased individualistic behavior of Keggin anions. As the fluence increased, the amount of the Keggin anions partially transformed to bronze also increased. Irradiation with vanadium also caused transformation to bronze‐like structure but with higher ratio of terminal W=Od bonds. The overall results show clear correlation between degree of structural modification of WPA and the calculated displacement per atom value. These results open possibilities for engineering new catalytically active structures of polyoxometalates with the help of ion beams.
In this study, 12‐tungstophosphoric acid (WPA) films (120 nm and 20 μm) were irradiated with hydrogen (10 keV) and swift heavy ions (Bi, Xe, and V, up to 710 MeV). The different energy/fluence combinations allowed controllable changes, from breaking of symmetry to bronze‐like structures, that were investigated in detail using Raman and Infrared spectroscopy. Structural changes of ion beam irradiated WPA might be beneficial for application in catalysis where the engineered structures can produce additional active sites for different reactions.
Industrialization today leads to a significant increase in the environmental pollution, with number of phenols, pesticides, paints, solvents and other organic pollutants with potentially carcinogenic ...effect in natural resources. Investigation of some new semiconductor materials and their photocatalytic properties for removal of pollutants is a challenging work. However, limited usage of photoactive materials still requires the testing of new materials with photoactive properties. The current work introduces the swift and easy approach for synthesis of (metal–free) N–doped carbon quantum dots in water using microwave reactor. Synthesis was performed from glucose water solution by heating in microwave reactor for only 1 min, at low temperature and applied microwave power. The synthesized N–doped carbon quantum dots show remarkable photocatalytic activity for removal of toxic organic dye (Rose Bengal) under visible light irradiation. Almost 93% of the dye degradation is achieved after only 30 min of radiation. The uninspected result, that the pH of the medium has a significant effect on the performance of the synthesized material in the presence of organic dye, indicates that dots show dual behavior. In the neutral and basic conditions, they have the ability to degrade organic dye, whereas, by shifting the medium pH into acidic medium, they form a stable conjugate with Rose Bengal.
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