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Enhancement of the luminescence of gold nanoclusters using gold nanorods is determined both experimentally and theoretically as a function of spacer thickness, spectral overlap, dimensions of nanorods and the specific position of nanoclusters on a nanorod.

Photoluminescent (PL) gold nanoclusters (AuNCs) show many advantages over conventional semiconductor quantum dots, however, their application potential is limited by their relatively low absorption cross-section and quantum yield. Plasmonic enhancement is a common strategy for improving the performance of weak fluorophores, yet in the case of AuNCs this method is still poorly explored. Here a robust synthetic approach to a compact plasmonic nanostructure enhancing significantly the PL of AuNCs is presented. Two gold nanostructures, AuNCs and plasmonic gold nanorods (AuNRs), are assembled in a compact core-shell nanostructure with tunable geometry and optical properties. The unprecedented degree of control over the structural parameters of the nanostructure allows to study the effects of several parameters, such as excitation wavelength, AuNC-AuNR distance, and relative loading of AuNCs per single AuNR. Consequently, a more general method to measure and evaluate enhancement independently of the absolute particle concentrations is introduced. The highest PL intensity enhancement is obtained when the excitation wavelength matches the strong longitudinal plasmonic band of the AuNRs and when the separation distance between AuNCs and AuNRs decreases to 5 nm. The results presented are relevant for the application of AuNCs in optoelectronic devices and bioimaging.

Photoluminescent materials are advanced cutting-edge heat-rejecting materials capable of reemitting a part of the absorbed light through radiative/non-thermal recombination of excited electrons to their ground energy state. Photoluminescent materials have recently been developed and tested as advanced non-white heat-rejecting materials for urban heat mitigation application. Photoluminescent materials has shown promising cooling potential for urban heat mitigation application, but further developments should be made to achieve optimal photoluminescence cooling potential. In this paper, an advanced mathematical model is developed to explore the most efficient methods to enhance the photoluminescence cooling potential through estimation of contribution of non-radiative mechanisms. The non-radiative recombination mechanisms include: (1) Transmission loss and (2) Thermal losses including thermalization, quenching, and Stokes shift. The results on transmission and thermal loss mechanisms could be used for systems solely relying on photoluminescence cooling, while the thermal loss estimations can be helpful to minimize the non-radiative losses of both integrated photoluminescent-near infrared (NIR) reflective and stand-alone photoluminescent systems. As per our results, the transmission loss is higher than thermal loss in photoluminescent materials with an absorption edge wavelength (λAE) shorter than 794 nm and quantum yield (QY) of 50%. Our predictions show that thermalization loss overtakes quenching in photoluminescent materials with λAE longer than 834 nm and QY of 50%. The results also show that thermalization, quenching, and Stokes shift constitute around 56.8%, 35%, and 8.2% of the overall thermal loss. Results of this research can be used as a guide for the future research to enhance the photoluminescence cooling potential for urban heat mitigation application.

Semiconductor nanoparticles proved to be an important material in the composition of modern technologies. The most important properties which shape these nanoparticles include not only their atomic composition and size, but also surface chemistry. Here, we present an environmentally friendly method of their surface modification. The proposed method does not require any possibly toxic chemicals, it relies solely on the use of water and air and an inexpensive plasma-generating system. Water treated by discharge is known to produce the so-called plasma-activated water, containing a complex mixture of water- and air-originating reactive species. We show that water treated by transient spark discharge in a vessel with restricted air flow leads to a novel chemical composition of plasma activated water, beneficial for the modification of the surface of nanoparticles. After the treatment of silicon nanoparticles with our plasma activated water, their photoluminescence quantum yield increases several times and their dispersibility in water is significantly improved. The modification is stable at laboratory conditions for at least several weeks and when the liquid is dried out from the sample. We demonstrate that the modification is caused by surface incorporation of nitrate-water complexes, which subsequently leads to a change of surface-oxide-related strain affecting the charge carrier radiative rates. The general applicability of the method is confirmed using commercial MgO and ZnO nanoparticles. Thus, the proposed method enables chemicals-free surface modification of nanoparticles and opens the door for a wide range of variations based on different liquids and discharge parameters.

Metal-halide perovskites feature very low deep-defect densities, thereby enabling high operating voltages at the solar cell level. Here, by precise extraction of their absorption spectra, we find t...

Application of highly absorptive construction materials is proved to be one of leading causes of urban overheating in big cities. To avoid the excessive heat by the conventional construction materials, several advanced heat-rejecting coating technologies were developed during the last decades. The main idea behind heat-rejecting coatings is to have colder coatings with the same appearance and colour of conventional coatings. One of the existing technologies for heat-rejecting coatings are advanced coatings with high solar reflection in the infrared range or so-called cool coatings. Recently, re-emission of the visible-range light by nano-scale semiconductors, known as Quantum Dots (QDs), were introduced as another effective heat-rejecting technology. In this paper, we showed that QDs also demonstrate a very high solar transmission in the near-infrared range, and therefore, a highly near-infrared reflective base layer can significantly improve their cooling potential. The high transmission value in the near-infrared range is due to the low absorption coefficient in the wavelengths longer than absorption edge wavelength (i.e. the wavelength corresponding to the bandgap energy) in semiconductors. We show that surface temperature reduction potential of CdSe/ZnS QDs film through fluorescent cooling is about 2.5 °C, which could be increased by another 8.1 °C with a highly near-infrared reflective base layer in a typical sunny day.

Application of fluorescent materials has proven to be an effective method for urban overheating mitigation due to their unique ability to re-emit a portion of the absorbed solar irradiation through photoluminescence (PL) effect. Herein, we introduced the idea of using quantum dots (QDs) as tunable fluorescent materials with potentially higher cooling capacity than their bulk counterparts and proposed a novel algorithm to model their thermo-optic behaviour under the sunlight. Our proposed method represents a major step forward in the understanding of the heat-rejection mechanism through PL effect and optimization of QDs fluorescent properties for urban overheating mitigation. Since it’s complicated to distinguish surface temperature reduction caused by reflection from that of PL effect, our developed algorithm could be used as a reliable tool for precise estimation of the PL effect contribution to heat dissipation.

There is an urgent quest for room-temperature qubits in nanometer-sized, ultrasmall nanocrystals for quantum biosensing, hyperpolarization of biomolecules, and quantum information processing. Thus far, the preparation of such qubits at the nanoscale has remained futile. Here, we present a synthesis method that avoids any interaction of the solid with high-energy particles and uses self-propagated high-temperature synthesis with a subsequent electrochemical method, the no-photon exciton generation chemistry to produce room-temperature qubits in ultrasmall nanocrystals of sizes down to 3 nm with high yield. We first create the host silicon carbide (SiC) crystallites by high-temperature synthesis and then apply wet chemical etching, which results in ultrasmall SiC nanocrystals and facilitates the creation of thermally stable defect qubits in the material. We demonstrate room-temperature optically detected magnetic resonance signal of divacancy qubits with 3.5% contrast from these nanoparticles with emission wavelengths falling in the second biological window (1000–1380 nm). These results constitute the formation of nonperturbative bioagents for quantum sensing and efficient hyperpolarization.

The main aim of this project is create an interactive map of seismic hazard of the territory of the Czech Republic and the system of its upgrading. The map will fulfill the recommendation of the International Atomic Energy Agency for evaluation of seismic hazard at the sites of nuclear facilities. It will serve as the background material during the process of approving of seismic safety of nuclear infrastructure. The interactive map will enable also to improve seismic hazard assessment for non-nuclear buildings, facilities and infrastructure. The system of continual upgrading will enable to include the new scientific results in the field of seismic hazard and experience from new earthquakes.Czech Republic is situated in an intraplate region with low seismicity. The seismic hazard is relatively low, but not negligible. The seismic hazard is evaluated by probabilistic seismic hazard method, including construction of logic tree and deriving of seismic hazard curves. In areas, where no or just a few weak events are recorded, but significant earthquakes can occur from both geological and seismological point of view, the concept of diffused seismicity is applied.Historical catalogs in weak-seismic regions cover a much shorter period than the average time between the strong (controlling) earthquakes. This cause a complicate evaluation of focal zone maximal magnitude parameter. Hence, a new method of maximal magnitude determination was developed. It uses Bayesian approach combining a priori information from wider region with historical earthquake catalogue resulting in probability distribution of maximum magnitude.For the evaluation of the local conditions, the new Vs30 map of Czech Republic is prepared. The map combines method of Wald and Allen (2007), using topographic slope as a proxy for seismic site conditions and amplification, and new Vs30 field measurements on multiple locations in the area of study.References:Wald, J.W. and Allen, T.I (2007): Topographic Slope as a Proxy for Seismic Site Conditions and Amplification, doi: 10.1785/0120060267.

The treatment of time-resolved (TR) photoluminescence (PL) decay kinetics is analysed in details and illustrated by experiments on semiconductor quantum dots, namely silicon nanocrystals (Si NCs). ...

Fluorophores functionalized with heavy elements show enhanced intersystem crossing due to increased spin-orbit coupling, which in turn shortens the fluorescence decay lifetime (tau(PL)). This phenomenon is known as the heavy-atom effect (HAE). Here, we report the observation of increased tau(PL) upon functionalisation of near-infrared photoluminescent gold nanoclusters with iodine. The heavy atom-mediated increase in tau(PL) is in striking contrast with the HAE and referred to as inverse HAE. Femtosecond and nanosecond transient absorption spectroscopy revealed overcompensation of a slight decrease in lifetime of the transition associated with the Au core (ps) by a large increase in the long-lived triplet state lifetime associated with the Au shell, which contributed to the observed inverse HAE. This unique observation of inverse HAE in gold nanoclusters provides the means to enhance the triplet excited state lifetime.

The optical properties of colloidal near-infrared (NIR) emitting gold nanoclusters (AuNCs) are thoroughly investigated at variable temperatures and excitation powers. Both absorption and photoluminescence (PL) excitation spectra reveal optical transitions expected from literature models of thiolated AuNCs – with the exception of the lowest energy transition which has the form of a featureless absorption tail partially overlapping with the PL band. The absorption cross section is determined via the PL saturation and PL modulation techniques to be in the range of 2–3 × 10−14 cm2 for excitation at 405 nm (relatively large value for such small clusters) and decreases ∼20 times toward 633 nm. Slow transient quenching (perfectly reversible) of PL is observed when the excitation power exceeds the saturation threshold, i.e. when the probability of achieving the second absorption in an excited AuNC before its relaxation is significant. A stable PL quenched level is reached within a fraction of a minute or a few minutes after the start of the excitation. Similar time intervals are needed for AuNCs to relax back to the original state in the dark. By comparing thermally-induced and light-induced PL decreases and PL kinetics speed up, we conclude that the transient quenching is due to heating caused by the dissipated excitation power. The light-induced PL amplitude reduction is much stronger (up to ∼80% under 405 nm, 60 W cm−2 excitation) than changes in PL decay time (∼20%), which is due to PL blinking and PL switching-off in a fraction of the AuNC ensemble. The potential application of these AuNCs in nanothermometry is discussed.

The great application potential of photoluminescent silicon nanocrystals, especially in biomedicine, is significantly reduced due to their limited radiative rate. One of the possible ways to overcome this limitation is enhancing the luminescence by localized plasmons of metallic nanostructures. We report an optimized fabrication of gold nanorod – silicon nanocrystal core–shell nanoparticles with the silica shell as a tunable spacer. The unprecedented structural quality and homogeneity of our hybrid nanoparticles allows for detailed analysis of their luminescence. A strong correlation between dark field scattering and luminescence spectra is shown on a single particle level, indicating a dominant role of the longitudinal plasmonic band in luminescence enhancement. The spacer thickness dependence of photoluminescence intensity enhancement is investigated using a combination of experimental measurements and numerical simulations. An optimal separation distance of 5 nm is found, yielding a 7.2× enhancement of the luminescence intensity. This result is mainly attributed to an increased quantum yield resulting from the Purcell enhanced radiative rate in the nanocrystals. The ease of fabrication, low cost, long-term stability and great emission properties of the hybrid nanoparticles make them a great candidate for bio-imaging or even targeted cancer treatment.

Made available in DSpace on 2020-12-12T02:36:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Herein we report the synthesis of highly-doped silver nanocluster in fluorophosphate glasses through the melting-quenching method in order to achieve sensitization with Tm3+ and Mn2+ ions. Blue and red emission belonging to Tm3+ (470 to 490 nm) and Mn2+ (550 to 750 nm) ions could be obtained via non-resonant excitation of Tm3+ and Mn2+. Slight decrease of the fluorescence decay times confirmed an energy transfer as a possible mechanism to explain the Tm3+ and Mn2+ emission. The composition of 5 mol% of AgNO3, 0.4 mol% of Tm2O3 and 0.2 mol% of MnF2 in our sample leads to distance between donor (silver nanoclusters) and acceptor (Tm3+-Mn2+) as short as 11 Å, which suggests that the main mechanism for blue and red emission from Tm3+ and Mn2+ is Förster Resonance Energy Transfer (FRET). The results presented here show that the studied material has potential application for multicolor generation as luminophore in white light emitting diodes (W-LED). Institute of Chemistry - São Paulo State University - UNESP Department of Chemical Physics and Optics Faculty of Mathematics and Physics Charles University, Ke Karlovu 3 Department of Chemistry and Chemical Engineering Chalmers University of Technology Institute of Chemistry - São Paulo State University - UNESP FAPESP: #2013/07793-6 FAPESP: #2016/16343-2 FAPESP: #2016/16900-9

Over the past decade, fluorescent gold nanoclusters (AuNCs) have witnessed growing popularity in biological applications and enormous efforts have been devoted to their development. In this protocol, a recently developed, facile method for preparation of water soluble, biocompatible, and colloidally stable near-infrared emitting AuNCs have been described in detail. This room-temperature, bottom-up chemical synthesis provides easily functionalizable AuNCs capped with thioctic acid and thiol-modified polyethylene glycol in aqueous solution. The synthetic approach requires neither organic solvents or additional ligand exchange nor extensive knowledge of synthetic chemistry to reproduce. The resulting AuNCs offer free surface carboxylic acids, which can be functionalized with various biological molecules bearing a free amine group without adversely affecting the photoluminescent properties of the AuNCs. A quick, reliable procedure for flow cytometric quantification and confocal microscopic imaging of AuNC uptake by HeLa cells also been described. Due to the large Stokes shift, proper setting of filters in flow cytometry and confocal microscopy is necessary for efficient detection of near-infrared photoluminescence of AuNCs.

Binuclear lanthanide complexes of Eu(III) and Sm(III) were obtained in the presence of chiral ligand 1,2-(R,R+S,S)-N,N'-bis(2-pyridylmethylene),2-diamine. An unusual structure of the Eu(III) compound with two lanthanide atoms connected through two chlorines was determined by X-ray crystallography. In solution, the dimer coexists with a monomeric complex, and the stability of the binuclear form depends on the solvent and concentration. The dimer-monomer equilibrium was monitored by circularly polarized luminescence (CPL) measured on a Raman optical activity (ROA) spectrometer, where both forms provided large CPL anisotropic ratios of up to 5.6×10-2 . Monomer formation was favored in water, whereas the dimer was stabilized in methanol. When mixed with adenosine phosphates, AMP gave much smaller CPL than ADP and ATP, indicating a high affinity of the Eu (III) complex for the phosphate group, which in connection with the ROA/CPL technique can be developed into a bioanalytical probe.

Power-dependent photoluminescence (PL) decay kinetics of silicon nanocrystals (Si NCs) in solid and liquid samples were studied under cw and pulsed excitation. The lifetime distribution and, consequently the measured PL kinetics are shown to depend on the excitation pulse duration until it is not sufficiently short (pulsed limit) or long (cw limit). These two excitation limits, however, are proven to excite different distributions of lifetime components and cannot be directly compared. We derive and experimentally confirm the equality of lifetimes averaged over amplitude and intensity for cw and pulsed excitation, accordingly. The absorption cross section (ACS) of Si NCs in solid and liquid samples is assessed and compared by two approaches under cw-excitation based on the treatment of power-modulated PL kinetics or PL amplitude saturation curves under low and moderate excitation powers, respectively. The discrepancy in extracted ACS values as well as the long-debated phenomena of incomplete PL saturation of matrix-embedded Si NCs is explained by a proposed model that is based on saturation of various components in an ensemble distribution at different excitation powers. The model finally allows us to explain the mystery of average decay lifetime dependence on excitation power in the non-linear power regime. By varying the excitation from cw to pulsed, we showed the reduction of average decay lifetime in the later case and attribute this to the increased relative PL contribution of fast lifetime components that results in at least one order of magnitude lower ACS values. Finally, exciting the solid sample with very high excitation powers, we detected a PL intensity decrease region that allowed us to extract the Auger lifetime which is about 170 ns.

We employ time-dependent photoluminescence (PL) and steady-state PL excitation (PLE) measurements to study the size-dependent optical properties of ultrasmall silicon carbide (SiC) nanoparticles (N...

Zinc oxide (ZnO) thin films deposited by atomic layer deposition (ALD) and a (0001)-oriented bulk-ZnO single-crystal are compared by ultrafast time-resolved and spectral photoluminescence spectroscopy as well as by luminescence quantum yield (QY) measurements. While the ALD-ZnO is intrinsically conductive, bulk-ZnO is electrically rather insulating. Nevertheless, PL spectra of both materials reveal similarities: A peak in the near-UV originating from inter-band transitions and a defect peak in the green-yellow spectral region associated to deep trap states. We investigate the dynamics and efficiency of these luminescence emissions to understand the interdependency of defects and the yet insufficiently understood conductivity mechanism of ALD-ZnO. Spectrally, a PL blueshift of the trap-mediated peak is observed for the transition from poor to good conductivity, which occurs with increasing ALD-deposition temperature. The quantum yield of ALD-ZnO is shown to be ~ 18-times lower and the luminescence lifetime of the UV-peak is ~ 14-times shorter compared to bulk-ZnO. We conclude that these properties are related to a significantly higher density of non-radiative defects, which might also represent electrically active scattering centers. These results indicate a new direction for further optimization of ALD-ZnO towards indium tin oxide (ITO)-compatible electrical conductivities by reducing or passivating these defects.

The western part of the Bohemian Massif hosts an intersection of two regional fault zones, the SW-NE trending Ohře/Eger Graben and the NNW-SSE trending Marianske Lazně Fault, which has been reactivated several times in the geological history and controlled the formation of the Tertiary Cheb Basin. The broader area of the Cheb Basin is also related to permanent seismic activity of ML 3+ earthquake swarms. The Eastern Marginal Fault of the Cheb Basin (northern segment of the Marianske Lazně Fault) separates the basin sediments and underlying granites in the SW from the Krusne Hory/Erzgebirge Mts. crystalline unit in the NE. We describe a detailed geophysical survey targeted to locating the Eastern Marginal Fault and determining its geometry in the depth. The survey was conducted at the Kopanina site near the Nový Kostel focal zone, which shows the strongest seismic activity of the whole Western Bohemia earthquake swarm region. Complex geophysical survey included gravimetry, electrical resistivity tomography, audiomagnetotellurics and seismic refraction. We found that the rocks within the Eastern Marginal Fault show low resistivity, low seismic velocity and density, which indicates their deep fracturing, weathering and higher water content. The dip of the fault in shallow depths is about 60° towards SW. At greater depths, the slope turns to subvertical with dip angle of about 80°. Results of geoelectrical methods show blocky fabric of the Cheb Basin and deep weathering of the granite bedrock, which is consistent with geologic models based on borehole surveys.

A small, inconspicuous scoria cone in western Bohemia, known as Komorni hůrka Hill, played a crucial role during the controversy between Plutonists and Neptunists over the origin of rocks in the first half of the nineteenth century. The year 2017 represents the 180th anniversary of one successful resolution of this debate: at the instigation of J.W. Goethe, adits were dug into this volcano to access its feeding system in order to observe whether volcanoes were fed by burning coal seams, or feeder dikes of magma. The adits into Komorni hůrka Hill were the first large earth-works with a solely scientific goal and with no commercial mining purposes. The basaltic feeder exposed in the adits decided definitively in favour of the Plutonists after decades of ongoing arguments with the Neptunists. Here, we summarize the overall history of this small volcano. A recently conducted ground geophysical survey confirmed the position of historical adits, marked on several archive sketches. The geophysical data, comprising ground magnetometry, electric resistivity tomography and refraction seismic profiles, also revealed the internal structure of the volcano, including the position of the feeder dike and the geometry of a lava flow emitted from the crater. With the position of these historical adits confirmed by geophysical survey, excavations can safely reopen these historical earth-works and provide access to a wider public. Komorni hůrka could then serve as an educational geosite to exhibit the structure of a small monogenetic volcano, as well as illustrating a stage in the history of Earth Sciences.

The increase in nonradiative pathways with decreasing emission energy reduces the luminescence quantum yield (QY) of near-infrared photoluminescent (NIR PL) metal nanoclusters. Efficient surface ligand chemistry can significantly improve the luminescence QY of NIR PL metal nanoclusters. In contrast to the widely reported but modestly effective thiolate ligand-to-metal core charge transfer, we show that metal-to-ligand charge transfer (MLCT) can be used to greatly enhance the luminescence QY of NIR PL gold nanoclusters (AuNCs). We synthesized water-soluble and colloidally stable NIR PL AuNCs with unprecedentedly high QY (similar to 25%) upon introduction of triphenylphosphonium moieties into the surface capping layer. By using a combination of spectroscopic and theoretical methods, we provide evidence for gold core-to-ligand charge transfer occurring in AuNCs. We envision that this work can stimulate the development of these unusually bright AuNCs for promising optoelectronic, bioimaging, and other applications.

The Sośnica Hill volcano is part of the Oligocene to Miocene (30.9–20.0 Ma) Strzelin volcanic field. It is located 100 km east of the Ohře Rift in the eastern part of the Fore-Sudetic Block, south of the town of Strzelin, Poland. Modern quarrying has exposed the sub-volcanic magma feeder system of the central part of the volcano and an extrusive volcanic succession that includes a 40 m thick sequence of lava flows and pyroclastic deposits that collectively form a complex scoria cone. Geophysical data (ground magnetometry and electric resistivity tomography (ERT)) reveal sharp linear anomalies that are interpreted to reflect normal faults dissecting the volcano. The ERT data map both high and low resistivity bodies, likely representing coherent clay-free dry rocks and partly argilized volcaniclastic deposits, respectively. Paleomagnetic data from 20 intrusive sites reveal two populations of reverse polarity site mean data; 11 sites are of low dispersion and yield a group mean direction that is discordant to the expected field direction, while six sites are highly scattered. Three sites did not yield interpretable results. We interpret the 11 sites as time-averaged field directions that are discordant to the expected field. The high dispersion of the remaining six sites are interpreted to indicate sub-volcanic deformation associated with the growth of the volcanic construct or multiple magma pulses over an extended period of time relative to secular variation. AMS data from 35 sites show a range of flow directions that vary across the quarry without an orderly pattern of fabric orientations. The flow pattern identified from dike paired margin data exhibits sub-vertical upward flow, sub-vertical downward, and moderately inclined northwest flow. Field observations and mapping indicate a complex development of the system in terms of styles of eruptive activity and structure of the final volcanic edifice. The activity included Strombolian and effusive phases, followed by phreatomagmatic, Hawaiian and again effusive eruptions. Such diversity of eruptive styles shows that the origin of the volcano is more complex than a simple, ‘textbook’ monogenetic scoria cone. Palaesoil on top of Strombolian deposits document a longer break in activity, after which eruptions resumed with different style; this is also not typical of monogenetic cones. The lateral variation in the volcanic succession suggests eruptions from several smaller, local vents. The complex subvolcanic magma flow patterns recorded in dikes match the variation of surface eruptive products and documents dynamically changing magma distribution paths in the near-surface and intra-cone part of the feeding system of the volcano.

Kashmir basin in the NW Himalaya is surrounded by the main Himalayan boundary faults, has very well documented historical earthquakes and a good instrumental earthquake record. However, the causative faults of these earthquakes except the 8 October 2005 Kashmir earthquake (M7.6) are not known. One of many historical earthquakes that have struck and caused damage and destruction in the Kashmir basin is the 30 May 1885 Kashmir earthquake (~M6.3). The extensive damage due to this earthquake was reported in the NW part of the basin and as usual the causative fault is not known and mapped. As the earthquake related geomorphic features are not preserved due to the high erosion rates in the Kashmir Himalaya, we mapped certain active fault strands using high resolution digital elevation models (DEM) and the Google Earth imagery, later complemented by the field investigation in the NW Kashmir. The Electrical Resistivity Tomography (ERT) was carried out at certain identified sites in the macroseismic epicentral area of the 1885 Kashmir earthquake. The results show a local active normal fault which was named as the NW Kashmir fault. The ERT results were confirmed by excavating a trench and an already existing road cut at the ERT sites. The results show that ERT is a very useful shallow geophysical method to detect faults in the Karewas. Karewas are the Plio-Pleistocene and Holocene (reworked by rivers), fluvio-lacustrine, soft and unconsolidated, sand-clay-conglomerate sediments, deposited as distinct table-land geomorphic features in the Kashmir basin and are significantly water saturated.

The most realistic information about the transparent sample such as a live cell can be obtained only using bright-field light microscopy. At high-intensity pulsing LED illumination, we captured a primary 12-bit-per-channel (bpc) response from an observed sample using a bright-field microscope equipped with a high-resolution (4872x3248) image sensor. In order to suppress data distortions originating from the light interactions with elements in the optical path, poor sensor reproduction (geometrical defects of the camera sensor and some peculiarities of sensor sensitivity), we propose a spectroscopic approach for the correction of this uncompressed 12-bpc data by simultaneous calibration of all parts of the experimental arrangement. Moreover, the final intensities of the corrected images are proportional to the photon fluxes detected by a camera sensor. It can be visualized in 8-bpc intensity depth after the Least Information Loss compression., 18 pages, 11 figures

The absorption cross section (ACS) of silicon nanocrystals (Si NCs) in single-layer and multilayer structures with variable thickness of oxide barriers is determined via a photoluminescence (PL) modulation technique that is based on the analysis of excitation intensity-dependent PL kinetics under modulated pumping. We clearly demonstrate that roughly doubling the barrier thickness (from ca. 1 to 2.2 nm) induces a decrease of the ACS by a factor of 1.5. An optimum separation barrier thickness of ca. 1.6 nm is calculated to maximize the PL intensity yield. This large variation of ACS values with barrier thickness is attributed to a modulation of either defect population states or of the efficiency of energy transfer between confined NC layers. An exponential decrease of the ACS with decreasing temperature down to 120 K can be explained by smaller occupation number of phonons and expansion of the band gap of Si NCs at low temperatures. This study clearly shows that the ACS of Si NCs cannot be considered as independent on experimental conditions and sample parameters.