Papers by ATHANASIOS VLESSIDIS
International Journal of Environmental Analytical Chemistry, Sep 26, 2017
Mikrochimica Acta, Oct 28, 2022
The cornerstone of nanomaterial-based sensing systems is the synthesis of nanoparticles with appr... more The cornerstone of nanomaterial-based sensing systems is the synthesis of nanoparticles with appropriate surface functionalization that ensures their stability and determines their reactivity with organic or inorganic analytes. To accomplish these requirements, various compounds are used as additives or growth factors to regulate the properties of the synthesized nanoparticles and their reactivity with the target analytes. A different rationale is to use the target analytes as additives or growth agents to control the formation and properties of nanoparticles. The main difference is that the analyte recognition event occurs before or during the formation of nanoparticles and it is based on the reactivity of the analytes with the precursor materials of the nanoparticles (e.g., metal ions, reducing agents, and coatings). The transition from the ionic (or molecular) state of the precursor materials to ordered nanostructured assemblies is used for sensing and signal transduction for the qualitative detection and the quantitative determination of the target analytes, respectively. This review focuses on assays that are based on analyte-mediated regulation of nanoparticles' formation and differentiate them from standard nanoparticlebased assays which rely on pre-synthesized nanoparticles. Firstly, the principles of analyte-mediated nanomaterial sensors are described and then they are discussed with emphasis on the sensing strategies, the signal transduction mechanisms, and their applications. Finally, the main advantages, as well as the limitations of this approach, are discussed and compared with assays that rely on pre-synthesized nanoparticles in order to highlight the major advances accomplished with this type of nano-sensors and elucidate challenges and opportunities for further evolving new nano-sensing strategies. Analyte-mediated nanoparticle formation • Seeding growth • Enzyme-induced growth • Chemical sensors and biosensors Abbreviations * Dimosthenis L. Giokas
Bioinorganic Chemistry and Applications, 2007
The progress of the research work of the author and his colleagues on the field of CL-emission ge... more The progress of the research work of the author and his colleagues on the field of CL-emission generated by pyrogallol oxidation and further application for the direct determination of periodate and indirect or direct determination of other compounds through flow-injection manifold/CL-detection set up is described. The instrumentation used for these studies was a simple flowinjection manifold that provides good reproducibility, coupled to a red sensitive photomultiplier that gives sensitive CL-detection. In addition, recent reports on studies and analytical methods based on CL-emission generated by periodate oxidation by other authors are included.
Chemosensors, 2021
Photography-based photometry is a technique developed to perform high throughput UV photometric a... more Photography-based photometry is a technique developed to perform high throughput UV photometric analysis without instrumental detectors in resource-limited settings. Its principle relies on the illumination of a sample with UV irradiation and then capturing the transmitted irradiation on a photosensitive paper surface. Therefore, the photosensitive surface acts as a detector for the determination of the concentration of analytes in the sample. This work aims to investigate the optimum photosensitive paper coatings for capturing the transmitted UV irradiation. To this end, photosensitive coatings based on silver, iron, and dichromate salts were tested using three assays of pharmaceutical and biochemical interest. The results from both calibrations, using standard solutions and the application in real samples, show that photosensitive coatings based on iron salts provide the best results. Importantly, the detection limits and the linear range of the calibration curves were better than...
Chemosensors, 2021
A new method for the determination of chloride anions in sweat is described. The novelty of the m... more A new method for the determination of chloride anions in sweat is described. The novelty of the method relies on the different photochemical response of silver ions and silver chloride crystals when exposed to UV light. Silver ions undergo an intense colorimetric transition from colorless to dark grey-brown due to the formation of nanosized Ag while AgCl exhibits a less intense color change from white to slightly grey. The analytical signal is obtained as mean grey value of color intensity on the paper surface and is expressed as the absolute difference between the signal of the blank (i.e., in absence of chloride) and the sample (i.e., in the presence of chloride). The method is simple to perform (addition of sample, incubation in the absence of light, irradiation, and offline measurement in a flatbed scanner), does not require any special signal processing steps (the color intensity is directly measured from a constant window on the paper surface without any imager processing) and...
Applied Sciences, 2021
This work describes a new, low-cost and simple-to-use method for the determination of free biothi... more This work describes a new, low-cost and simple-to-use method for the determination of free biothiols in biological fluids. The developed method utilizes the interaction of biothiols with gold ions, previously anchored on micellar assemblies through electrostatic interactions with the hydrophilic headgroup of cationic surfactant micelles. Specifically, the reaction of AuCl4− with the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) produces an intense orange coloration, due to the ligand substitution reaction of the Br− for Cl− anions, followed by the coordination of the AuBr4− anions on the micelle surface through electrostatic interactions. When biothiols are added to the solution, they complex with the gold ions and disrupt the AuBr4−–CTAB complex, quenching the initial coloration and inducing a decrease in the light absorbance of the solution. Biothiols are assessed by monitoring their color quenching in an RGB color model, using a flatbed scanner operating in transmitt...
29-P-06-acidity characterization of dealuminated H-ZSM-5 zeolites by isopropanol dehydration
Studies in Surface Science and Catalysis, 2001
Publisher Summary This chapter discusses the acidity characterization of dealuminated H-ZSM-5 zeo... more Publisher Summary This chapter discusses the acidity characterization of dealuminated H-ZSM-5 zeolites by isopropanol dehydration. A series of dealuminated ZSM-5 zeolites with various framework silicon/aluminium (Si/Al) ratios are prepared by different methods. The number of acid sites that correspond to the high-temperature desorption peak of the ammonia-temperature-programmed desorption (TPD) spectra of all the dealuminated samples is in 1:1 mole analogy to the framework Al (FAl), irrespective the degree and the type of dealumination method. The catalytic activity of the H-ZSM-5 zeolites for isopropanol dehydration is linearly related to the number of acid sites that correspond to the FAl-content (Bronsted acidity). The Si–Al amorphous phase that is formed in the high-temperature steamed samples affects activity and induces different product selectivity for propene and diisopropyl ether.
Water Research, 2001
Abstract}Clinoptilolite tuffs from areas in Thrace region of Greece are compared with synthetic z... more Abstract}Clinoptilolite tuffs from areas in Thrace region of Greece are compared with synthetic zeolites NaY and NH 4 Y for the uptake of N4-ethyl-N4-(2-methansulphonamidoethyl)-2-methyl-1,4-phenylenediamin (sesquisulphate, monohydrate) with the trade name CD-3 for the purpose to be used for clean-up and recycling photo-finishing and photo-developing washwaters. The cation-exchange capacity is found to be 6.15-11.1 mg/g for zeoliferous tuffs at equilibrium concentration of 50 ppm CD-3 in aqueous solution compared to 65.0 mg/g of NaY and 48.2 mg/g for NH 4 Y synthetic zeolites corresponding to the removal of CD-3 from 120 to 200 l of 50 ppm aqueous solution per kg of natural zeoliferous tuff; this capacity is only 6-10 times lower than type-Y synthetic zeolite. Initial rates of uptake are 20.8 mg/l/min for natural and 38.5 mg/l/min for synthetic zeolites. Regeneration levels of 55, 23, 35, and 33% are obtained for MCH, SF, NaY, and NH 4 Y, respectively. The rapid and almost complete uptake of CD-3 from its aqueous solutions at low CD-3 concentrations by the natural zeolites is promising for such an application.
Analytica Chimica Acta, 2015
With the increasing interest in the health benefits arising from the consumption of dietary produ... more With the increasing interest in the health benefits arising from the consumption of dietary products rich in antioxidants, there exists a clear demand for easy-to-use and cost-effective tests that can be used for the identification of the antioxidant power of food products. Paper-based analytical devices constitute a remarkable platform for such expedient and low-cost assays with minimal external resources but efforts in this direction are still scarce. In this work we introduce a new paper-based device in the form of a sensor patch that enables the determination of antioxidant activity through analyte-driven on-paper formation of gold nanoparticles. The principle of detection capitalizes, for the first time, on the on-paper nucleation of gold ions to its respective nanoparticles, upon reduction by antioxidant compounds present in an aqueous sample. The ensuing chromatic transitions, induced on the paper surface, are used as an optical "signature" of the antioxidant strength of the solution. The response of the paper-based sensor was evaluated against a large variety of antioxidant species and the respective dose response curves were constructed. On the basis of these data, the contribution of each species according to its chemical structure was elucidated. For the analysis of real samples, a concentration-dependent colorimetric response was established against Gallic acid equivalents over a linear range of 10 mM-1.0 mM, with detection limits at the low and ultra-low mM levels (i.e. <1.0 mM) and satisfactory precision (RSD = 3.6-12.6%). The sensor has been tested for the assessment of antioxidant activity in real samples (teas and wines) and the results correlated well with commonly used antioxidant detection methods. Importantly, the sensor performed favorably for long periods of time when stored at moisture-free and low temperature conditions without losing its activity thus posing as an attractive alternative to the assessment of antioxidant activity without specialized equipment. The use of the sensor by non-experts for a rapid assessment of natural products in field testing is envisioned. Importantly, we demonstrate for the first time that analyte-mediated growth of nanomaterials directly on the paper surface could open new opportunities in paper-based analytical devices.
Talanta, 2015
In this work we describe the fabrication of nanostructured electrocatalytic surfaces based on pol... more In this work we describe the fabrication of nanostructured electrocatalytic surfaces based on polyethyleneimine (PEI)-supported rhodium nanoparticles (Rh-NP) over graphite screen-printed electrodes (SPEs) for the determination of hydrogen peroxide in the presence of oxygen. Rh-NP, electrostatically stabilized by citrate anions, were immobilized over graphite SPEs, through coulombic attraction on a thin film of positively charged PEI. The functionalized sensors, polarized at 0.0V vs. Ag/AgCl/3M KCl, exhibited a linear response to H2O2 over the concentration range from 5 to 600μmolL(-1) H2O2 in the presence of oxygen. The 3σ limit of detection was 2μmolL(-1) H2O2, while the reproducibility of the method at the concentration level of 10μmolL(-1) H2O2 (n=10) and between different sensors (n=4) was lower than 3 and 5%, respectively. Most importantly, the sensors showed an excellent working and storage stability at ambient conditions and they were successfully applied to the determination...
Water Resources Management, 2005
The effect of land use patterns on river water quality was studied in three different river basin... more The effect of land use patterns on river water quality was studied in three different river basins located in Epirus, Northwestern Greece. Studies were conducted from October 2000 to September 2001. During this period, the parameters chemical oxygen demand (COD), biological oxygen demand (BOD), NO - 2 , NO - 3 , NH + 4 and PO 3- 4 were measured, employing standard methods of analysis. The results were subjected to principal component analysis (PCA) for the estimation of the underlying variable correlations and were further explored by means of cluster analysis. The values of the above parameters were also compared with those awkward in the Fresh Water Fisheries Directive (78/659/EEC). It was found that the phosphate content was much higher than the upper limiting criteria for eutrophication for salmonid waters, whereas nitrate levels were lower than the permissible criteria according to the Nitrates Directive 91/676/EEC for drinking water. The inorganic nutrient load was mostly attributed to sites that drain agricultural areas, especially during winter and spring. The organic matter was due to urban activities during autumn.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2004
The concept of liquid coacervate extraction (LCE) is deployed to accomplish metal speciation afte... more The concept of liquid coacervate extraction (LCE) is deployed to accomplish metal speciation after appropriate derivatization of the target metallic species. The method involves the partitioning of the hydrophobic metal chelates, produced from the reaction of Cr with APDC, in the vesicular aggregates formed from an anionic surfactant with alkaline earth metals and a cosurfactant, which are separated from the bulk aqueous phase. Under the established experimental conditions, the method offers high reproducibility, very low detection limits and recoveries in the range of 95 -104%. Moreover, the method affords high tolerance for EDTA, which is used as a masking agent in order to avoid interferences from co-extracted metals. Validation of the outlined method was performed by analysing a certified reference material (BCR 544) yielding recoveries higher than 94% for both Cr oxidation states.
Microchimica Acta, 2007
This study describes the design and optimisation of a field flow system for the in-situ collectio... more This study describes the design and optimisation of a field flow system for the in-situ collection and on-line determination of phosphate, nitrate and nitrite by flow injection analysis-spectrophotometry. The method is based on the initial determination of phosphate as its phosphoantimonylmolybdenum blue complex which is then oxidized on-line by nitrite and the decrease in absorbance is monitored at 880 nm. Nitrate is determined as the difference between total and initial nitrite content in a separate flow after reduction to nitrite in a cadmium reductive column. The calibration curves were linear in the range 0-2.00 mg L À1 P-phosphate, 0-10.00 mg L À1 nitrite and 0-7.00 mg L À1 nitrate with correlation coefficients of 0.9979, 0.9993 and 0.9995, respectively. The detection limits, calculated as 3S=N, were 0.15 mg L À1 for Pphosphate, 0.17 mg L À1 for nitrite and 0.09 mg L À1 for nitrate. The reproducibility was below 3.0% (n ¼ 7). Method validation in the analysis of natural water and wastewater samples revealed that it can efficiently be applied to the determination of the target analytes, with recoveries in the range of 92-108%.
Microchimica Acta, 2006
A kinetic-potentiometric method is described for the quantitative assay of formaldehyde (HCHO) in... more A kinetic-potentiometric method is described for the quantitative assay of formaldehyde (HCHO) in pharmaceutical and industrial preparations. It is based on the reaction of HCHO with (ethylenediamine)-Cu(II)sulfate [Cu(CH 2 NH 2 ) 2 (H 2 O) 2 ] Á SO 4 . The changes in potential, resulting from the release of the Cu(II) cations, are monitored with a Cu(II)-ion selective electrode. The calibration curve for the HCHO is linear in the concentration range 50-250 mg L À1 , with a limit of detection of 8.5 mg L À1 . The method shows very good reproducibility with an RSD of 2.6% for successive injections (n ¼ 5) of 150 mg L À1 HCHO primary solution, while it is interference free. The method was successfully tested in various industrial and pharmaceutical preparations.
Journal of Chromatography A, 2005
The ability of vesicle-coated silica to aid the extraction of organic compounds from water prior ... more The ability of vesicle-coated silica to aid the extraction of organic compounds from water prior to liquid chromatographic analysis is presented for the first time. The method is based on the formation of silica supported cationic multi-lamellar vesicles of gemini surfactants inherently ensuring the presence of hydrophilic and hydrophobic sites for the partitioning of analytes bearing different properties. Method development is illustrated by studying the adsolubilization of UV absorbing chemicals from swimming pool water. Due to the requirement for external energy input (intense shearing) a method based on solid-phase dispersion (SPD) was applied producing better results than off-line solid-phase extraction (SPE). Meticulous investigation of the experimental parameters was conducted in order to elucidate the mechanisms behind the proposed extraction pattern. Analyte recoveries were quantitative under the optimum experimental conditions offering recoveries higher than 96% with RSD values below 5%.
Industrial & Engineering Chemistry Research, 2000
Dealuminated zeolite samples prepared by different methods are characterized by different techniq... more Dealuminated zeolite samples prepared by different methods are characterized by different techniques, and the structural and acidic characteristics are investigated in an effort to identify the parameters that decide their structural and acidic characteristics. The investigation gave evidence that the structure breakdown of the parent type-Y zeolite is mainly dependent on the degree of dealumination, but the nature of extraframework aluminum (EFAl) species formed is dependent on the type of dealumination procedure. Monomeric Al species and oligomeric Si,Al species were formed by steam treatment at relatively low and high temperatures, respectively. Aluminosilicate phases of Si/Al ratios 2.0-4.0 and 8.0 were found in SiCl 4 -treated and ammonium hexafluorosilicate (AHFS)-treated samples, respectively. EFAl species of octahedral and tetrahedral coordination were observed by NMR spectra in steam and SiCl 4 -treated samples. High degrees of dealumination within each type of treatment resulted in loss of microporosity of the crystalline material, but the increase of mesoporous and/or macroporous structure was dependent on the type of dealumination. The increase of macroporous structure was the result of crystallite agglomerates formed during the procedure. The number of acid sites determined by the ammonia temperature-programmed desorption method, under appropriate experimental conditions, matched with the FAl content of the dealuminated H-Y samples that do not contain a significant amount of EFAl species. The loss of strong acid sites with the degree of dealumination is evidenced to be dependent on the method of dealumination. Dealumination by AHFS up to ca. 50% does not affect the number of strong acid sites considerably, in contrast to the weak/medium acid sites which decrease almost linearly with a FAl decrease. At higher degrees of dealumination achieved by steaming or SiCl 4 -treatment, both weak/medium and strong acid sites decrease steeply with FAl decrease. There is evidence that the produced EFAl-species by the different methods have different acidic properties and result in low stoichiometries of adsorbing ammonia probe molecules. The EFAl species produced by the SiCl 4 method result in more acidic H-Y zeolite catalysts compared to the high-temperature steamed samples.
Desalination, 2007
A combination of non-parametric explanatory procedures and pattern recognition techniques is intr... more A combination of non-parametric explanatory procedures and pattern recognition techniques is introduced in this study as an alternative tool to the assessment of sedimentary P fractionation. The complex raw data matrix was treated with a series of parametric and non-parametric techniques such as correlation analysis, cluster analysis, factor analysis/principle components analysis, discriminant analysis, multidimensional scaling, Kruskal-Wallis analysis of variance and non-parametric median test. Each of these procedures has been directed towards the identification of specific mechanisms that control P biogeochemistry in the river sediment. Non-parametric tests were proven as a very powerful tool in interpreting temporal variations of the data in a short-term basis as opposed to previous procedures predicting seasonal or annual changes. On the other hand, parametric techniques were not always able to delineate a reduced number of indicator variables responsible for the large variations in sediment quality, necessitating the application of various techniques in order to interpret the intricate mechanisms occurring in the sediment phase. The examined procedures provide the basis for identifying the patterns of sedimentary P associated with seasonal and spatial patterns, pollution sources as well as differentiate between natural and non-natural inputs, presenting an alternative approach for environmental quality assessments.
Bioinorganic Chemistry and Applications, 2007
The progress of the research work of the author and his colleagues on the field of CL-emission ge... more The progress of the research work of the author and his colleagues on the field of CL-emission generated by pyrogallol oxidation and further application for the direct determination of periodate and indirect or direct determination of other compounds through flow-injection manifold/CL-detection set up is described. The instrumentation used for these studies was a simple flow-injection manifold that provides good reproducibility, coupled to a red sensitive photomultiplier that gives sensitive CL-detection. In addition, recent reports on studies and analytical methods based on CL-emission generated by periodate oxidation by other authors are included.
Land-Based Classification of Herb's Origin Based on Supervised and Unsupervised Pattern Recognition of Plant and Soil Chemical Profiling
Analytical Letters, 2010
ABSTRACT In this work, a series of supervised and unsupervised pattern recognition techniques are... more ABSTRACT In this work, a series of supervised and unsupervised pattern recognition techniques are assessed for the first time as a tool in order to elaborate a common approach able to classify different plant species based on a common pattern determined by their geographical origin. For this reason, soil samples and extracts from various parts of 7 self-sown indigenous Greek plants were collected in nature from two regions (highlands and insular) in NW Greece. Based on the chemical profiling of each species and the respective soil matrix composition, the identification of similarities and dissimilarities on a regional basis were pursued. The results indicate that hierarchical cluster classification and discriminant analysis using the chemical profile of inorganic elements and soil matrix composition provide the basis for the provision of an area-specific geographic marker that enables the classification of different herbs based on their origin with high discrimination efficiency.
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Papers by ATHANASIOS VLESSIDIS