Temperature Measurements by Wavelength Modulation Diode Laser Absorption Spectroscopy with Logarithmic Conversion and 1<i>f</i> Signal Detection

A new version of a sensor for temperature measurements in the case of strong laser intensity fluctuation was developed. It was based on tunable diode laser absorption spectroscopy (TDLAS) with wavelength modulation, logarithmic conversion of the absorption signal, and detection of the first harmonic of the modulation frequency. The efficiency of the technique was demonstrated under experimental conditions with excess multiplicative noise. Temperature was evaluated from the ratio of integrated absorbance of two lines of the water molecule with different lower energy levels. Two algorithms of data processing were tested, simultaneous fitting of two spectral ranges with selected absorption lines and independent fitting of two absorption lines profiles. The correctness of the gas temperature evaluation was verified by simultaneous measurements with a commercial thermocouple. An error in temperature evaluation of less than 40 at 1000 K was achieved even when processing a single scan of the diode lasers

FRET Pumping of Rhodamine-Based Probe in Light-Harvesting Nanoparticles for Highly Sensitive Detection of Cu2+

In this work we presented novel strategy for increasing the performance of popular fluorescent probes on the basis of rhodamine-lactam platform. This strategy is based on the incorporation of probe molecules into the light-harvesting nanoparticles to pump modulated optical signal by Förster resonant energy transfer. Using the commercially available Cu2+ probe as a reference chemical, we have developed an efficient approach to significantly improve its sensing performance. Within obtained nanoparticles coumarin-30 nanoantenna absorbs excitation light and pumps incorporated sensing molecules providing bright fluorescence to a small number of emitters, while changing the probe-analyte equilibrium from liquid-liquid to solid-liquid significantly increased the apparent association constant, which together provided a ~100-fold decrease in the detection limit. The developed nanoprobe allows highly sensitive detection of Cu2+ ions in aqueous media without organic co-solvents usually required for dissolution of the probe, and demonstrate compatibility with inexpensive fluorometers and the ability to detect low concentrations with the naked eye

A First Record of Lower Jurassic (Toarcian) Coleoid Jaws in Siberia

In the present paper, we describe several coleoid jaws discovered in the lower Toarcian black shales, cropping out along the Vilyui River (Yakutia, Russia). This is the first record of a Lower Jurassic coleoid jaw outside Europe and the first report of such a finding from the Mesozoic of Siberia. The described coleoid jaws demonstrate the same mode of preservation and morphology as the coeval jaws previously reported from Europe. Their preservation in Siberia became possible due to the widespread occurrence of black shale facies associated with the early Toarcian oceanic anoxic event (TOAE)

The Study of Uranium Accumulation in Marine Bottom Sediments: Effect of Redox Conditions at the Time of Sedimentation

To evaluate the effect of redox conditions at the sedimentation stage on uranium content and U/TOC ratio in marine source rocks, we analyzed the accumulation of uranium in modern marine bottom sediments formed in different redox conditions. The behavior of uranium from bottom sediments formed in oxidizing and sub-oxidizing settings has been studied on the sediments of the Upper Pleistocene–Holocene age accumulated in the coastal area of the White Sea (Kandalaksha Gulf). We studied the content of uranium, Eh, pH, TOC, C, H, N, and S element and isotope compositions and other parameters in two sampled columns of bottom sediments at a depth of 0–2.5 m. The composition of sediments was typical for the shelf zone where marine genesis mixes with the continental run-off. The upper layer of sediments (0–50 cm) were characterized by oxidizing conditions (Eh ~ 400 mV); with the increase in depth, redox conditions changed from oxidizing to reducing (−0 ÷ −200 mV). The uranium concentration in the upper layer was 1–1.5 ppm, U/TOC ratio varied in the range of 0.8–1.1 ppmU/%TOC. The uranium content and U/TOC ratio increased up to the values of 2.6 ppm and 1.4 ppmU/%TOC at a depth of 0.5–2.5 m, respectively, but the general content of uranium in the studied environment was close to the values characterizing continental run-off. The results obtained for the White Sea sediments were compared with the sediment of the Black Sea, formed in the anoxic conditions of hydrogen sulfide contamination. In these conditions, the uranium content varied from 10 to 20 ppm. The obtained data were interpreted using thermodynamic modeling of the uranium forms in the seawater at different pH and Eh. This study demonstrated that the change of redox conditions from oxidizing to reducing leads to increased uranium content due to a decrease in uranium’s solubility in water. These results show that oxidation–reduction potential could be one of the most important factors controlling uranium content in black shales formed in the marine environment

Light Harvesting Nanoprobe for Trace Detection of Hg2+ in Water

The continuously increasing flow of toxic heavy metals to the environment due to intensive industrial activity and tightening requirements with regard to the content of metal ions in drinking and discharged waters urges the development of affordable and sensitive devices to the field control of pollutants. Here, we report a new thiated Rhodamine-lactam probe for Hg2+ detection and demonstrate how its sensitivity can be increased via the incorporation of the probe molecules into the optically transparent siloxane-acrylate coatings on polymethyl methacrylate and, alternatively, into the water-dispersible light-harvesting FRET nanoparticles (NPs), in which dye cations are separated by fluorinated tetraphenylborate anions. We have shown that the optimization of the FRET NPs composition had allowed it to reach the antenna effect of ~300 and fabricate &ldquo;off/on&rdquo; sensor for Hg2+ ion determination in aqueous solutions with the detection limit of ~100 pM, which is far below the maximum permissible concentration (MPC) of mercury in drinking water recommended by the World Health Organization. Although this work is more proof-of-concept than a ready-to-use analytical procedure, the suggested approaches to fabrication of the FRET NPs based on the popular rhodamine-lactam platform can be used as a background for the development of low-cost portable sensing devices for the extra-laboratory determination of hazardous metal ions

Light Harvesting Nanoprobe for Trace Detection of Hg²⁺ in Water

The continuously increasing flow of toxic heavy metals to the environment due to intensive industrial activity and tightening requirements with regard to the content of metal ions in drinking and discharged waters urges the development of affordable and sensitive devices to the field control of pollutants. Here, we report a new thiated Rhodamine-lactam probe for Hg2+ detection and demonstrate how its sensitivity can be increased via the incorporation of the probe molecules into the optically transparent siloxane-acrylate coatings on polymethyl methacrylate and, alternatively, into the water-dispersible light-harvesting FRET nanoparticles (NPs), in which dye cations are separated by fluorinated tetraphenylborate anions. We have shown that the optimization of the FRET NPs composition had allowed it to reach the antenna effect of ~300 and fabricate “off/on” sensor for Hg2+ ion determination in aqueous solutions with the detection limit of ~100 pM, which is far below the maximum permissible concentration (MPC) of mercury in drinking water recommended by the World Health Organization. Although this work is more proof-of-concept than a ready-to-use analytical procedure, the suggested approaches to fabrication of the FRET NPs based on the popular rhodamine-lactam platform can be used as a background for the development of low-cost portable sensing devices for the extra-laboratory determination of hazardous metal ions

Modeling Changes in the Composition of River Water with Discharged Wastewater: A Case Study in NW Russia

The technogenic impact of the development of the Lomonosov diamond deposit is associated with the discharge of quarry and drainage water into the river, which has a special conservation status. Earlier studies on the composition of bottom sediments showed that there are signs of increased accumulation of heavy metals and radionuclides at wastewater discharge sites. The purpose of this work was to predict changes in the composition of surface water and bottom sediment in the river during the further development of mining operations with brackish and salty water captured by drainage systems, the presence of which was established in the zone of their future influence. For this, a simulation of changes in the composition of the water in the river was carried out using the GEOCHEQ software package by minimizing the free energy of the system using a convex simplex algorithm. It was found that the maximum salinity of surface water can reach 1.51 g/L. In this case, the MPC of Cl−, Na+, SO42−, Mg2+, Sr, V, and U can be exceeded for fishery watercourses. The genetic basis of the accumulation of these components in solutions for mixing was considered. According to the calculations, when about 5000 m3/h of drainage water is discharge d into the river, the mass of precipitated chemical elements will be 56–191 t/h, including up to 2.1 t/h of iron; therefore, accumulation in the discharge zone must be controlled