Titanium dioxide (TiO2) nanoparticles, have been routinely used in cosmetic and sunscreen applications, due to their ability to absorb in the UV spectrum. Nevertheless, one of the main disadvantages ...has been the generation of reactive oxygen species (ROS), especially the hydroxyl radical, upon photoexcitation of titania. In this work, we investigate TiO2 nanoparticles doped with 0.6–0.7% manganese (Mn), based in the more stable rutile polymorph of titania. In particular, while the anatase crystal form has the ability to destroy almost any organic matter under UV illumination, rutile is less photoreactive, and with Mn doping its photoactivity is reduced further. In particular, we study its optical, structural and semiconducting properties via the Seebeck effect and show that the material displays p-type characteristics. This is very significant because it shifts the energy levels with respect to formation of hydroxyl free radicals. This ensures that for Mn doped p-type titania it is not energetically possible for the hole created in the valence band by photoexcitation to create an OH. free radical and this may explain its low photoreactivity. It also means that this material can act as a very effective scavenger for hydroxyl free radicals.
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•Pt(acac)2 precursor ensured even PtNP dispersion on α-MnO2 nanorods.•Surprisingly, increasing the Pt loading induced a transition from α-MnO2 to Mn5O8.•XPS showed a decrease in ...Pt(IV) and Pt(II) with Pt loading, while Pt(0) increased.•Pt/MnO2 nanorods displayed excellent catalytic activity for 4-NP to 4-AP reduction.•The presence of Pt(IV) is not a limiting factor for the catalytic conversion of 4-NP to 4-AP.
α-MnO2 nanorods (NRs) were synthesized by microwave irradiation and used as supports for platinum nanoparticles by wet impregnation with Pt(acac)2 as precursor. XRD analysis revealed that the samples without platinum (sample MP0) and with 1 % platinum (sample MP1) contained tetragonal α-MnO2. Samples with 3 % (sample MP3) and 5 % (sample MP5) of platinum contained monoclinic Mn5O8 in addition to α-MnO2, with Mn5O8 dominating in sample MP5. Rietveld analysis showed that the lattice parameters of α-MnO2 increased slightly with Pt loading. SEM and STEM showed that higher Pt loadings resulted in shorter nanorods and different sizes and dispersions of PtNPs on their surface. XPS results showed a decrease in Pt(IV) and Pt(II) concentration with Pt loading, while Pt(0) increased. NEXAFS results showed the presence of Mn(II) in MP3 and MP5, which is consistent with XRD results detecting Mn5O8. The catalytic activity of the Pt/α-MnO2 nanorods was tested in the catalytic reduction of 4-nitrophenol to 4-aminophenol. MP1, with the lowest platinum content, exhibited the highest mass normalized rate constant kapp/mPt of 1.8 × 104 s−1 g−1. The study suggests that the presence of Pt(IV) is not a limiting factor for the catalytic reduction of 4-NP to 4-AP.
The world has been facing an increase in various natural hazards. The coastal regions are recognized as one of the most vulnerable due to high population pressure and climate change intensity. ...Mediterranean countries have one of the most burnable ecosystems in the world, one of the most exposed to pluvial floods, and have the highest erosion rates within the EU. Therefore, the aim of this study was to develop the first multihazard susceptibility model in Croatia for the Sali settlement (island of Dugi otok). The creation of a multi-hazard susceptibility model (MHSM) combined the application of geospatial technology (GST) with a local perception survey. The methodology consisted of two main steps: (1) creating individual hazard susceptibility models (soil erosion, wildfires, pluvial floods), and (2) overall hazard susceptibility modeling.
Multicriterial GIS analyses
and the
Analytical Hierarchy Process
were used to create individual hazard models. Criteria used (32) to create models are derived from very-high-resolution (VHR) models. Two versions of MHSM are created: 1) all criteria with equal weighting coefficients and 2) weight coefficients determined based on public perception. According to MHSM 1, most of the research (58%) area is moderately susceptible to multiple hazards. Highly and very highly susceptible areas are 27% of the drainage basin and are mostly located near roads and houses. MHSM 2 reveals similar results to MHSM 1. The public perceives that the research area is the most susceptible to wildfires. The wildfire ignition risk is ranked as moderate (3.00) with a standard deviation of 1.16. Pluvial flood risk is ranked low (2.78), with a standard deviation of 1.15. The risk of soil is most inferior (2.24) with a standard deviation of 0.91. The the most significant difference between public perception and the GIS-MCDA model of hazard susceptibility is related to soil erosion. However, the accuracy of the soil erosion model was confirmed by ROC curves based on recent traces of soil erosion in the research area. The proposed methodological framework of multi-hazard susceptibility modeling can be applied, with minor modifications, to other Mediterranean countries.
The geographic information system (GIS) is, at the global level, recognized as one of the best ICTs for implementation in the subject of geography. The application of GIS in the Republic of Croatia ...(RH) lags behind developed countries. The main objective of this research was to examine the attitudes of secondary school students and geography teachers regarding the introduction of GIS in the educational system process. In the period from 3 October 2021 to 27 January 2022, a survey questionnaire was conducted in 30 secondary schools in the RH on a sample of 611 students and 96 teachers. The results have showed that both teachers and students have a positive attitude toward the introduction of GIS for the purpose of teaching geography. More than 80% of teachers believe that GIS is not sufficiently represented in the high school and geography curricula which is recognized as one of the most important factors which limit GIS implementation. A majority (77%) of teachers are not using GIS on any teaching level, which is not surprising since both surveyed teachers and students have poor knowledge of GIS, although teachers rated their knowledge a little higher. Teachers perceive students’ interest in GIS exactly as students express it; predominantly indifferent. The most important factors limiting the implementation of GIS are recognized as: a lack of necessary GIS software and licenses; not knowing how to use GIS; and an insufficient number of teaching units dedicated to GIS in the geography curricula. An equal percentage of both teachers and students believe that there are prerequisites for GIS implementation in their schools. One of the basic prerequisites for GIS implementation is that education authorities need to “see” GIS as an important part of geography and include it more in school curricula. In almost all countries where GIS has been implemented in schools, difficulties in its implementation have been documented.
A series of fluorescent mono- (
14
) and bis-pyrene derivatives (
57
) were synthesized and their photophysical and self-aggregation properties in solution were fully investigated by UV-vis and ...fluorescence spectroscopies and dynamic light scattering (DLS). While in dilute DMSO mono-pyrene derivatives
14
show the characteristic features of monomer emission, bis-pyrene derivatives
57
display both monomer and excimer emissions, the latter attributable to a dynamic process. The gelation behaviour of these compounds was also studied, and only mono-pyrene leucine derivative
1
was found to display efficient gelation in aromatic solvents, such as toluene and
p
-xylene, and in a polar solvent mixture, water/DMSO (4:1 v/v). Finally, mono-pyrenes
14
showed no apparent cytotoxic impact on A549 and RD cell lines; derivatives
15
showed accumulation within both live and fixed cells, and macropinocytosis was found to be the main pathway for
5
to enter into the cells.
Seven newly designed mono- and bis-pyrene derivatives with varying amino acid units self-assembled into fluorescent organic nanoparticles and were used for imaging in live cells.
Iron(III) chloride deoxygenated alkaline aqueous colloidal solutions in the presence of 2-propanol and dextran sulfate were γ-irradiated with doses of 36 and 130 kGy. The dose rate was ∼31 kGy h−1. ...The samples isolated by washing with water mainly consisted of γ-FeOOH (lepidocrocite), δ-FeOOH and schwertmannite. The samples isolated by washing with ethanol contained mainly α-FeOOH (goethite), δ-FeOOH (feroxyhyte) and iron(III) hydroxide sulfate. At lower dose (36 kGy) magnetite (Fe3O4) was formed. The samples isolated by admixing glycerol consisted of the intermediate phases Fe(OH)2, GR(SO42−) and non-stoichiometric FeS1-x (mineral name mackinawite). The amounts of Fe(II) in glycerol-isolated solid samples were 60.5% and 82.6% as determined by Mössbauer spectroscopy at doses of 36 and 130 kGy, respectively. The amount of Fe2+ in the acidified solutions containing dissolved γ-irradiation products was determined using potassium permanganate titration. The amounts of Fe2+ in acidified solutions were 72.0% and 92.0% at doses of 36 and 130 kGy, respectively. Thus, although the conventionally isolated powders consisted exclusively of Fe(III) products, the high reducing conditions upon γ-irradiation were confirmed by capturing the Fe(II) intermediate phases and by quantitative determinations of ferrous ions in the solid samples and solutions containing dissolved γ-irradiation products.
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•Dextran sulfate plays active role in radiolytic synthesis of magnetic iron oxides.•γ-FeOOH, δ-FeOOH and schwertmannite were isolated by washing with water.•α-FeOOH, δ-FeOOH and iron(III) hydroxide sulfate were isolated with ethanol rinsing.•Intermediate phases Fe(OH)2, GR(SO42−) and FeS1-x were isolated by glycerol.•Fe(II) intermediate phases oxidized to Fe(III) products by conventional isolation.
This study presents a micro-scale approach for the cropland suitability assessment of permanent crops based on a low-cost unmanned aerial vehicle (UAV) equipped with a commercially available RGB ...sensor. The study area was divided into two subsets, with subsets A and B containing tangerine plantations planted during years 2000 and 2008, respectively. The fieldwork was performed on 27 September 2021 by using a Mavic 2 Pro UAV equipped with a commercial RGB sensor. The cropland suitability was performed in a two-step classification process, utilizing: (1) supervised classification with machine learning algorithms for creating a vegetation mask; and (2) unsupervised classification for the suitability assessment according to the Food and Agriculture Organization of the United Nations (FAO) land suitability standard. The overall accuracy and kappa coefficients were used for the accuracy assessment. The most accurate combination of the input data and parameters was the classification using ANN with all nine input rasters, managing to utilize complimentary information regarding the study area spectral and topographic properties. The resulting suitability levels indicated positive suitability in both study subsets, with 63.1% suitable area in subset A and 59.0% in subset B. Despite that, the efficiency of agricultural production can be improved by managing crop and soil properties in the currently non-suitable class (N1), providing recommendations for farmers for further agronomic inspection. Alongside low-cost UAV, the open-source GIS software and globally accepted FAO standard are expected to further improve the availability of its application for permanent crop plantation management.
The accurate extraction of a coastline is necessary for various studies of coastal processes, as well as for the management and protection of coastal areas. Very high-resolution satellite imagery has ...great potential for coastline extraction; however, noises in spectral data can cause significant errors. Here, we present a newly developed Coastal Extraction Tool (CET) that overcomes such errors and allows accurate and time-efficient automated coastline extraction based on a combination of WorldView-2 (WV-2) multispectral imagery and stereo-pair-derived digital surface model (DSM). Coastline extraction is performed and tested on the Iž-Rava island group, situated within the Northern Dalmatian archipelago (Croatia). Extracted coastlines were compared to (a) coastlines extracted from state topographic map (1:25,000), and (b) coastline extracted by another available tool. The accuracy of the extracted coastline was validated with centimeter accuracy reference data acquired using a UAV system (Matrice 600 Pro + MicaSense RedEdge-MX). Within the study area, two small islets were detected that have not been mapped during the earlier coastline mapping efforts. CET proved to be a highly accurate coastline mapping technique that successfully overcomes spectral-induced errors. In future research, we are planning to integrate data obtained by UAVs infrared thermography (IRT) and in situ sensors, measuring sea and land surface temperatures (SST and LST), into the CET, given that this has shown promising results. Considering its accuracy and ease of use, we suggest that CET can be applied for automated coastline extraction in other large and indented coastal areas. Additionally, we suggest that CET could be applied in longitudinal geomorphological coastal erosion studies for the automated detection of spatio-temporal coastline displacement.
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•Glucosamine binds to gold nanoparticles obtained from laser ablation in liquid.•Aggregation of glucosamine at 10 mM concentration causes new UV–VIS band at 625 nm.•SERS spectra of ...glucosamine in clean gold colloid were obtained for 0.1 mM and 1 mM glucosamine concentrations.•Strongest SERS bands are at 1563, 1586 and 1652 cm−1 (fron C-NH3+ bending modes), at 1165 cm−1 (C-N stretching coupled with C-C stretching motion) and at 1075 cm−1 (C-O stretching coupled with ring C-C stretching mode)
The binding of glucosamine to gold in water solutions of glucosamine hydrochloride mixed with clean colloidal gold nanoparticles obtained by laser ablation in liquid was studied using surface-enhanced Raman scattering (SERS), dynamic light scattering (DLS) and UV–VIS spectroscopy. The purpose of this study was to establish whether the binding of charged aminogroup to gold nanoparticles (AuNPs) is taking place, and if it does, how can it be identified by means of SERS.
The average size of dried gold nanoparticles was (20 ± 4) nm determined by averaging the sizes observed in transmission electron microscopy micrographs, which is smaller than the average size of gold nanoparticles in water solution as determined by DLS: (52 ± 2) nm. Upon adding the glucosamine solutions to gold colloid, average hydrodynamic diameter of ions was slightly larger for 0.1 mM glucosamine solution (55 ± 2 nm), while it increased to (105 ± 22) nm in the case of 1 mM solution, and was (398 ± 54) nm when 10 mM glucosamine solution was added.
Most prominent Raman bands observed both for 0.1 mM and 1 mM glucosamine solutions were located at 1165 cm−1, 1532 and 1586 cm−1 and assigned to C-N coupled with C-C stretching, and C-NH3+ deformation angles bending. In SERS spectrum of 1 mM GlcN+ solution, two strong bands at 999 and 1075 cm−1 were found and attributed to C-Oring stretching coupled with C-NH3+ bending (999 cm−1) and to dominantly C-O stretching vibration. The differences in SERS spectra are attributed to different number of glucosamine molecules that attach to gold nanoparticles and their orientation with respect to the metal particle surface, partly due to presence of beta anomers protonated at anomeric oxygen position. The assignment of glucosamine bands was further corroborated by comparison with vibrational spectra of alpha and beta glucose and of polycrystalline powder of glucosamine hydrochloride. For all three substances comprehensive calculation of vibrational density of states was conducted using density functional theory. Benchmark bands for polycrystalline glucose anomers distinction are 846 and 915 cm−1 for alpha glucose, and 902 cm−1 for beta glucose. However, the bands observed in SERS spectra of 0.1 mM glucosamine solution at 831, 899, and 946 cm−1 or in 1 mM solution at 934 cm−1 cannot be easily identified as belonging either to alpha or beta glucosamine anomer, due to complexity of atomic motions involved. The identification of vibrational bands associated with –CNH3+ group will aid SERS studies on amino acids, especially in cases when several atomic groups could possibly bind to AuNPs.
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•γ-irradiation was explored for the synthesis of magnetic iron oxide/Au NPs.•A redox reaction occurs between solid-state Fe(OH)2 and Au3+ ions.•Obtained nanostructures consist of ...feroxyhyte nanodiscs decorated with AuNPs.•Feroxyhyte@Au material shows a high catalytic activity for the reduction of 4-NP.
γ-irradiation was used as an effective and environmentally friendly technique for the synthesis of magnetic iron oxide/Au nanostructures. Firstly, alkaline iron(III) precursor solutions, in the presence of 2-propanol and DEAE-dextran, were purged with nitrogen and γ-irradiated to doses of 14 and 75 kGy, which resulted in the reduction of Fe3+ to Fe2+ ions and formation of Fe(II)/Fe(III) or Fe(II) iron (hydr)oxide phases. After irradiation, gold nanoparticles (AuNPs) were attached to the surface of the magnetic nanostructures by in situ reduction of Au3+ with radiolytically formed Fe2+. At 75 kGy, simultaneous oxidation of Fe(OH)2 formed on irradiation and reduction of Au3+ led to the formation of superparamagnetic feroxyhyte (δ-FeOOH) nanodiscs decorated with well distributed, 11–24 nm AuNPs. The experiments performed with and without Fe(III) precursor and 2-propanol or tert-butanol as scavenger and in different atmospheres (N2, N2O) confirmed the main role of Fe2+ in Au3+ reduction. The catalytic activity of the δ-FeOOH/Au nanostructures was tested for the reduction of 4-nitrophenol to 4-aminophenol. Increasing the amount of added Au3+ enhanced the catalytic activity of the samples, but up to a certain amount depending on the size of formed AuNPs.
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