Hybrid Metal-Dielectric-Metal Sandwiches for SERS Applications

The development of efficient plasmonic nanostructures with controlled and reproducible surface-enhanced Raman spectroscopy (SERS) signals is an important task for the evolution of ultrasensitive sensor-related methods. One of the methods to improving the characteristics of nanostructures is the development of hybrid structures that include several types of materials. Here, we experimentally investigate ultrathin gold films (3–9 nm) near the percolation threshold on Si/Au/SiO2 and Si/Au/SiO2/graphene multilayer structures. The occurring field enhanced (FE) effects were characterized by a recording of SERS signal from Crystal Violet dye. In this geometry, the overall FE principally benefits from the combination of two mechanisms. The first one is associated with plasmon excitation in Au clusters located closest to each other. The second is due to the gap plasmons’ excitation in a thin dielectric layer between the mirror and corrugated gold layers. Experimentally obtained SERS signals from sandwiched structures fabricated with Au film of 100 nm as a reflector, dielectric SiO2 spacer of 50 nm and ultrathin gold atop could reach SERS enhancements of up to around seven times relative to gold films near the percolation threshold deposited on a standard glass substrate. The close contiguity of the analyte to graphene and nanostructured Au efficiently quenches the fluorescent background of the model compound. The obtained result shows that the strategy of combining ultrathin nano-island gold films near the percolation threshold with gap plasmon resonances is promising for the design of highly efficient SERS substrates for potential applications in ultrasensitive Raman detection.

Historical lead glass in museum collections: determination of the composition by a portable X-ray fluorescence analyzer

A method for the determination of the glass composition in the systems PbO – SiO2 and K2O – PbO – SiO2 with different additives present both in historical and modern art glass is considered. Development of a non-destructive method for determining the glass composition in conditions of museum storage is an important goal for museum practice. We propose a method for determining the composition of those glasses using a portable X-ray fluorescence analyzer (XRF). To select the optimal software suitable for measurements, we have synthesized a number of standard glass samples with the composition determined by ICP-AES. A glass sample of was dissolved in an autoclave in a mixture of nitric, hydrofluoric, and perchloric acids. The lead content in standard samples was simultaneously determined gravimetrically after fusion of the sample with sodium carbonate. Using XRF measurements of standard samples we development of a method for determination of the glass composition with an accuracy sufficient to assign the glass to one of the groups of historical glasses. The results obtained can be used for attribution of lead glass products. The content of potassium oxide in historical samples was estimated by XRF method using two independent programs with subsequent averaging of the data obtained. When using our method, the error of potassium, silicon and lead determination does not exceed 10%, which is sufficient for a museum description and attribution of an item. The developed procedure was tested in analysis of the items from the collection of the State Museum of Ceramics («Kuskovo Estate of the 18th century»).

The development of crosslinked gelatin thin films as controlled release matrices

The aim of this thesis was to develop gelatin-based thin films that may be used as matrices for the controlled release of bioactive compounds. There were three objectives to this research: i) develop a method to generate the thin films ii) experimentally quantify the release of a fluorescent marker from these films, and iii) implement a mathematical model to characterize the release of the fluorescent marker. To achieve the first objective, a novel method of developing thin films was implemented where sub-micron thickness films affixed to standard glass slides were crosslinked with genipin, a naturally-occurring fixative. Gel thickness measured using atomic force microscopy (AFM) varied from 350 to 650 nm irrespective of the concentration of genifin added. AFM-based surface roughness decreased with increasing genipin concentration. Release behavior of a fluorescent marker from the thin films demonstrated a strong influence of genipin concentration on release kinetics, with greater genipin leading to slower release. A mathematical model for the water transport into, and fluorescent marker release from, the genipin-crosslinked gelatin films was developed and successfully implemented with both the water ingress (swelling) and marker release being effectively characterized by the model.

The development of crosslinked gelatin thin films as controlled release matrices

The aim of this thesis was to develop gelatin-based thin films that may be used as matrices for the controlled release of bioactive compounds. There were three objectives to this research: i) develop a method to generate the thin films ii) experimentally quantify the release of a fluorescent marker from these films, and iii) implement a mathematical model to characterize the release of the fluorescent marker. To achieve the first objective, a novel method of developing thin films was implemented where sub-micron thickness films affixed to standard glass slides were crosslinked with genipin, a naturally-occurring fixative. Gel thickness measured using atomic force microscopy (AFM) varied from 350 to 650 nm irrespective of the concentration of genifin added. AFM-based surface roughness decreased with increasing genipin concentration. Release behavior of a fluorescent marker from the thin films demonstrated a strong influence of genipin concentration on release kinetics, with greater genipin leading to slower release. A mathematical model for the water transport into, and fluorescent marker release from, the genipin-crosslinked gelatin films was developed and successfully implemented with both the water ingress (swelling) and marker release being effectively characterized by the model.

MO319BEDSIDE URINE SEDIMENT EXAMINATION IN IMMUNOGLOBULIN A NEPHROPATHY PATIENTS PERFORMED BY NEPHROLOGISTS

Background and Aims Urine sediment microscopy is mostly abandoned by nephrologists nowadays, however it is an important diagnostic tool in kidney and urinary tract diseases. The aim of this study is to emphasize the benefits of urine microscopy performed by a nephrologist. Method A prospective cohort study at Pauls Stradins Clinical University Hospital Nephrology center included patients with histologically confirmed diagnosis of IgA nephropathy from 1st January 2020 till December 2020. Appropriately collected urine samples were examined using manual microscopy within an hour after sample collection and by automated urinalysis. Samples were centrifuged at 4000 rpm for 4 minutes, the supernatant urine was carefully decanted, 1 - 1,5 ml of the left urine was mixed by gentle agitation and placed on a standard glass slide with a cover slip. Sample examination was performed using low (magnification x10) and high power (magnification x40) using brightfield microscopy with a minimum of 10 fields. Results A total of 37 patients (24 men, mean age 42.7 ± 10.9 years) were included in the study. 59.5 % of patients (n = 22) had hematuria based on automated urine sediment analysis and 62.2 % (n = 23) of patients had hematuria based on manual urine microscopy. 45.9 % of patients (n=17) had dysmorphic erythrocytes, 13.5 % of patients (n = 5) had isomorphic red blood cells (RBC) and 40.5 % of patients (n = 15) did not have RBC in urine samples by manual urine microscopy. 54.2 % (13/24) of men and 30.8 % (4/13) of women had dysmorphic RBC in urine. Conclusion Manual urine sediment examination was more sensitive than automated analysis. Majority of IgA nephropathy patients have active urine sediment with hematuria and dysmorphic RBC. Manual microscopy remains an effective and reliable method that can be easily and quickly performed by nephrologists.

Fluorescence Enhancement on Silver-Plated Plasma Micro-Nanostructured 3D Polymeric Microarray Substrates for Multiplex Mycotoxin Detection

Oxygen plasma micro-nanostructured poly(methyl methacrylate) (PMMA) slides were modified through silver microparticle deposition to create microarray substrates that enhance the emitted fluorescence intensity. Silver deposition relied on a commercially available reagent and was completed in two 30-min incubation cycles of the substrate with the reagent. The fluorescence enhancement achieved using these substrates over flat PMMA slides was determined through the development of a microarray for the multiplexed detection of four mycotoxins, aflatoxin B1, ochratoxin A, fumonisin B1, and deoxynivalenol. It was shown that the implementation of silver-plated oxygen plasma micro-nanotextured PMMA substrates increased the signals obtained for aflatoxin B1 and ochratoxin A by approximately 2.8 times, 5.6 times for deoxynivalenol, and 16-times for fumonisin B1, compared to flat PMMA substrates. Most notably, this signal increase was not accompanied by a significant increase in the non-specific signal. In addition, the spot repeatability both across a single slide as well as between different slides was high, with coefficients of variation lower than 12%. The slides were also stable for at least three months, thus offering a microarray substrate with improved properties compared to standard glass slides, regarding both the absolute spot fluorescence intensity and between spots repeatability.

Pulsed Magnetron Sputtering of Strongly Thermochromic VO2-Based Coatings with a Transition Temperature of 22 °C onto Ultrathin Flexible Glass

The reversible semiconductor-to-metal transition of vanadium dioxide (VO2) makes VO2-based coatings a promising candidate for thermochromic smart windows, reducing the energy consumption of buildings. This paper deals with maximizing the application potential of these coatings in terms of their performance, an industry-friendly preparation technique, and an industrially relevant substrate. We present a scalable sputter deposition technique for the preparation of strongly thermochromic ZrO2/V0.984W0.016O2/ZrO2 coatings on ultrathin flexible glass and standard glass at a relatively low substrate surface temperature (330 °C) and without any substrate bias voltage. The V0.984W0.016O2 layers were deposited by a controlled high-power impulse magnetron sputtering of a V target, combined with a simultaneous pulsed dc magnetron sputtering of a W target. We explain the fundamental principles of this technique using the discharge characteristics measured for both discharges. We characterize the coating structure (X-ray diffraction) and a wide range of optical properties (spectrophotometry and spectroscopic ellipsometry). We find that the coatings combine a transition temperature of 22 °C, a luminous transmittance approaching 50%, a modulation of the solar energy transmittance over 10% and a temperature-independent color. The results in general, and the successful transfer from a standard glass to the ultrathin flexible glass in particular, are crucial for future applications of the coatings on smart windows.

Validation of a method to quantify microfibres present in aquatic surface microlayers

Many of the methods for microplastics quantification in the environment are criticised creating problems with data validity. Quantification of microplastics in the surface microlayer of aquatic environments using glass plate dipping holds promise as a simple field method, but its efficiency has yet to be validated. We tested a standard glass plate dipping method to assess recovery of four common polymer microfibres and two common natural fibres, under three different salinities (freshwater, brackish water, saltwater). Overall recovery rates were low (26.8 ± 1.54%) but higher recoveries were observed under saltwater treatments (36.5 ± 3.01%) than brackish water (24.5 ± 1.92%) or freshwater (19.3 ± 1.92%). The fibre types showed different recovery rates, with acrylic yielding significantly higher recovery rates (37.0 ± 2.71%) than other fibres across treatments. No clear relationship between the density of the fibres and the recovery efficiency was seen. We suggest that, where this method is used for monitoring microplastics, the results will typically underestimate the total amount present, but that recovery is sufficiently consistent to allow comparison of differences between sampling locations. When comparing data across river-estuarine or similar transects salinity should be monitored to account for salinity-induced differences in sampling recovery.

Determination of the Composition of Substances Migrating from Plugs Based on Bromo-Butyl Rubber into Infusion and Injection Preparations

The results of experimental studies of the composition of individual substances migrating from medical rubber plugs produced both in and abroad based on technical bromobutyl rubber are presented. The quantitative content of volatile organic compounds related to species impurities of gasoline was determined by gas chromatography from a standard glass bottle sealed with a sterile stopper based on bromobutyl rubber. The method of atomic emission spectroscopy was used to determine (indirect) the presence of organometallic, organosulfur and metal-inorganic compounds that did not pass through chromatographic columns, and the presence of organometallic, organosulfur and metal-inorganic compounds was determined by the content of metal and non-metal cations. The results of mass spectral studies of extracts of aqueous extracts from plugs based on bromobutyl rubber showed that they contain impurities of bromo-alkanes and bromo-arenes, which are direct-acting carcinogens.