The work is dedicated to fabrication and study of SERS-active nanocomposites based on aluminum hydroxide with incorporated copper nanoparticles (CuNP; 10±2 nm). The initial CuNP and the final composite were characterized using SEM, EDX, STM, and absorbance spectroscopy in UV-visible range. The application of incorporation enabled to improve temporal stability of SERS-activity of the CuNP against oxidation to around 80 times compare to colloidal CuNP; the composite is SERS-active for more than 8 days. The value of Raman enhancement was found around 8×106 that is comparable with the values for silver and gold based SERS substrates. The applicability of the final composite for chemical analysis was demonstrated by SERS detection of some drugs, such as antitumor (methotrexate) and antibacterial drugs (lincomycin, sulfadimethoxine, ceftriaxone). The analytes were detected at concentrations which have to be detected at physiological conditions in urine (50‒100 μg/mL) after medical treatment.
Creatinine (CRN) is the component of human biofluids (urine, blood) which is a clinically important indicator for evaluation of various diseases, e.g., renal (dis)functions. This work is dedicated to application of molecularly imprinted silica gel (MISG) as a CRN-selective sorbent for solid phase extraction to improve SERS based detection of CRN in urine. MISG was prepared using sol-gel process in the presence of a template (CRN) and aluminum ions which served as a doping agent to create recognition sites. Spectrophotometry studies showed that the combination of doping and imprinting improves sorption capacity ~3 times. We found that doping plays a key role and imprinting without doping does not lead to sorption improvement at all. Hydroxylamine stabilized silver nanoparticles were used as SERS substrate and the maximal CRN signal (i.e., analysis sensitivity) was found in alkaline media. Also, addition of alkali leads to dissolution of MISG matrix that was used to release CRN molecules and speed-up of analysis by skipping elution step. SERS results also demonstrate that MISG possesses the maximal sorption in comparison with silica gels fabricated without imprinting and/or doping. Therefore, the final analysis protocol implies solid phase extraction of CRN from a solution with further pH adjusting of the MISG-CRN complex and SERS detection of the released CRN. The protocol testing using model CRN solution and a urine sample demonstrated possibility for CRN detection at physiologically relevant concentrations and significant reduction of SERS background after extraction step.
The aim of the work is the investigation of bending on the properties of hypothetical one-atom-thick copper clusters (CC) (with 10 and 22 atoms). Time-dependent density functional theory with PBE0 functional and lanl2dz basis set were used for all calculations. The bending was performed by changing angle between copper atoms from 180° to 144° and 163.7° (2° step size) for CC with 10 and 22 atoms, correspondingly. The dependences of absorbance spectra in UVvisible-NIR range (400-2000 nm range) and various energetic characteristics (final energy, chemical potential, and binding energy) on bending angle were investigated. Non-bended (linear) clusters were assigned as references. First, absorbance spectra of all CC contain interband transitions (3d→4sp) in UV-visible range (below 600 nm). Linear configuration of CC also contain intensive absorbance band in NIR region (at 900 and 1700 nm for CC with 10 and 22 atoms) which is associated with 4s electron oscillations along clusters (longitudinal transitions). Significant dumping of low energy 4s transitions (HOMO→LUMO) and interband transitions in the range 600‒500 nm was observed during the bending of CC. Obtained results are in agreement with experimental results for 2D copper nanostructures from literature. We explain such influence of bending by formation merging 4s orbitals which form new 4s oscillations in-plane of bending (in the case of ring-like CC – diametral oscillations). An influence of bending on energy, stability, and chemical potential (Fermi level) of CC was also investigated and discussed.
The aim of this work was the fabrication of nanolabels (SERS-nanotags) which are used for chemical analysis by means of surface-enhanced Raman spectroscopy (SERS), and registration of their SERS spectra inside photonic crystal fibers (PCF). The SERS nanotags fabrication included synthesis of silver nanoparticles with subsequent deposition of Raman active layer (thiol-group contained aromatic compound) and protecting layer composed of silica shell. Finally, SERS spectra of the SERS nanotags were registered inside PCF in order to determine the value of fiber-enhancement of the Raman signal and to estimate analytical potential of this combination.
The article contains description of several demonstration experiments connected with application of light scattering (LS) for investigation of optical properties of nanoparticles solutions. The demonstrations are based on the usage of laser pointers with different wavelengths (405, 532, and 650 nm) for observing of light scattering and absorbance by various nanoparticles (silver, gold, sulfur, and cadmium selenide). These experiments were used during short course for secondary school students ("Introduction to Nanotechnology") and applied as hands-on activities in order to introduce students to methods of investigation of nanostructures. The demonstrations (included to the course) were tested during summer-camp school (in 2015 and 2016) and in club in chemistry (2016) for secondary school students (15–17 years old).
The aim of this report is detection of model compound, rhodamine 6G (R6G), in blood and urine samples using surfaceenhanced Raman spectroscopy (SERS) as a detection tool and liquid-liquid extraction (LLE) for improving quality of SERS analysis (SERS-LLE combination). SERS substrate is a plasmonic nanomaterial which possesses drastic increasing of Raman spectrum intensity (106‒108) of any molecule adsorbed onto its surface. Here we used citrate stabilized silver nanoparticles as SERS substrate and synthesized them applying wet chemical approach. Before SERS measurements, blood and urine samples were artificially contaminated with R6G using 50 and 500 ng/mL concentrations for both samples. In order to reduce detectable concentrations of R6G and improve signal-to-noise ratio, we applied LLE which allows us to separate R6G from the matrix mixture and increase the analyte concentration. Four different LLE protocols were used and the most efficient one was found. Obtained results showed usefulness of SERS-LLE combination for chemical analysis of body fluids with level of detectable concentration down to tens ng/mL.
Application of different methods for formation of microcontainers containing iodine is proposed in this paper. Two types of microcontainers: microemulsions and microparticles have been investigated, conditions and methods for obtaining microcontainers were optimized.
Microparticles were formed by layer-by-layer method with cores of calcium carbonate (CaCO3) as templates. Incorporation of complexes of iodine with polymers (chitosan, starch, polyvinyl alcohol) into core, shell and hollow capsules was investigated and loadings of microparticles with iodine were estimated. It was found that the complex of iodine with chitosan adsorbed at CaCO3 core is the most stable under physiological conditions and its value of loading can be 450 μg of I2 per 1 g of CaCO3. Moreover, chitosan was chosen as a ligand because of its biocompatibility and biodegradability as well as very low toxicity while its complex with iodine is very stable. A small amount of microparticles containing a iodine–chitosan complex can be used for prolonged release of iodine in the human body since iodine daily intake for adults is around 100 μg.
"Oil-in-water" emulsions were prepared by ultrasonication of iodinated oils (sunflower and linseed) with sodium laurilsulfate (SLS) as surfactant solution. At optimal conditions, the homogenous emulsions remained stable for weeks, with total content of iodine in such emulsion being up to 1% (w/w). The oil:SLS ratio was equal to 1:10 (w/w), optimal duration and power of ultrasound exposure were 1.5 min and 7 W, correspondingly. Favorable application of iodized linseed oil for emulsion preparation with suitable oil microdroplets size was proved.
New SERS-active materials were obtained by preparation of alumina with embedded silver nanoparticles and their application both as sorbents for pre-concentration and SERS platforms was studied. The influence of ionic strength on Ag NPs size, absorption spectra and SERS signal was investigated. Synthesized materials were examined by Raman spectroscopy, scanning electron microscopy, and UV-visible spectroscopy. The optimal conditions for SERSmeasurements were chosen. Synthesized materials were applied for pre-concentration of model analytes (Rhodamine 6G, folic acid and pyrene) and their SERS detection directly within the sorbent. It was shown that the recovery of analytes could be improved by alumina modification. The combination of surface-enhanced Raman spectroscopy with preconcentration is a promising instrument for analytical applications.
In this article we have applied liquid-liquid extraction (LLE) as a sample preparation technique for detection of sulfadimethoxine (one of sulfonamide drugs) in urine using surface-enhanced Raman spectroscopy (SERS). SERS substrate based on silver nanoparticles has been prepared by citrate reduction of silver nitrate. Obtained calibration curve (SERS intensity vs. sulfadimethoxine concentration) has been used for detection of sulfadimethoxine in human urine samples artificially contaminated by sulfadimethoxine. Three different solvents (ethyl acetate, diethyl ether, chloroform) have been used for LLE performance tests. Chloroform being found as the most effective one based on calculation of recoveries after SERS measurements. Thus we would like to propose fast (less than 20 minutes), simple and sensitive (detection limit up to 1 μg/ml) test for detecting sulfa drugs in urine using a combination of SERS with LLE with sample volume as low as 100 μL. Such test can be applied for evaluation of the degree of drug extraction from human body and half-life of such drug applied in the course of therapeutic treatments of certain diseases.
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