Biological molecules at surfaces

Effective atomic numbers for photon energy absorption, , and for photon interaction, , have been calculated by a direct method in the photon‐energy region from 1 keV to 20 MeV for biological molecules, such as fatty acids (lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic, arachidonic, and arachidic acids), nucleotide bases (adenine, guanine, cytosine, uracil, and thymine), and carbohydrates (glucose, sucrose, raffinose, and starch). The and values have been found to change with energy and composition of the biological molecules. The energy dependence of the mass attenuation coefficient, , and the mass energy‐absorption coefficient, , is shown graphically and in tabular form. Significant differences of between and occur in the energy region 5–100 keV. The reasons for these differences, and for using rather than in calculations of the absorbed dose, are discussed.

Siliconization is defined as a surface treatment process, the objective of which is to prevent undesirable interactions between the treated surface and biological macromolecules. Literature review reveals that siliconization encompasses several different methods which produce surfaces with different characteristics. The potential for variation in biological interaction as a result of different methods is demonstrated for whole blood. Polydimethylsiloxane, octadecylsilsesquioxane, chlorinated dimethylsiloxane and several treated surfaces were compared for relative blood protein adsorption and hemolysis.

Various metal sulphides were selected for gamma and neutron shielding prediction by (Phy-X and NGCAL). The gamma parameters calculated by both software programs in the studied energy range were found to be identical, with differences (Δ% less than 1%) between both models. The Mass Attenuation Coefficient (MAC), Mean Free Path (MFP), Half Value Layer (HVL), Tenth Value Layer (TVL), and Effective Atomic Number (Z eff) were calculated. Ag 2 S was a superior neutron and photon attenuator because it contains two silver ions with the highest density, mean atomic number, and metal composition in addition to the lowest (S%) among all sulphides under evaluation. Additionally, the Ag 2 S monoclinic network is fabricated from (2Ag +) linked to one (S 2-). Therefore, the presence of heavy packed ions in the unit cell resulted in more gamma attenuation. The Z eff variation with the energy range of 0.015-15 MeV may be associated with the density, mean atomic number, composition (%) or weight fraction, total atomic cross-section, crystal geometry and elemental packing of each molecule. It can be concluded that Ag 2 S was the superior attenuator between the sulphides under prediction, especially at higher energies. The Gamma Protection Efficiency (GPE, %) was also calculated for the gamma shielding subject based on the Linear Attenuation Coefficient (LAC) data presented in the Beer-Lamberts law: GPE% = (1-e^(-µx)) * 100, where the thickness was assumed. The GPE% increased with increasing thickness and decreased with increasing energy. Also, silver sulphide showed the highest GPE among the other tested materials. The GPE% of the thermal or fast neutrons was also calculated, where the increasing order was SnS, SnS 2 , ZnS, MoS 2 , As 2 S 3 , CuFeS 2 , FeS, CoS, and Ag 2 S for thermal neutrons and SnS 2 , SnS, MoS 2 , As 2 S 3 , ZnS, CuFeS 2 , FeS, Ag 2 S, and CoS for fast neutrons.

Various metal sulphides were selected for gamma and neutron shielding prediction by (Phy-X and NGCAL). The gamma parameters calculated by both software programs in the studied energy range were found to be identical, with differences (Δ% less than 1%) between both models. The Mass Attenuation Coefficient (MAC), Mean Free Path (MFP), Half Value Layer (HVL), Tenth Value Layer (TVL), and Effective Atomic Number (Z eff) were calculated. Ag 2 S was a superior neutron and photon attenuator because it contains two silver ions with the highest density, mean atomic number, and metal composition in addition to the lowest (S%) among all sulphides under evaluation. Additionally, the Ag 2 S monoclinic network is fabricated from (2Ag +) linked to one (S 2-). Therefore, the presence of heavy packed ions in the unit cell resulted in more gamma attenuation. The Z eff variation with the energy range of 0.015-15 MeV may be associated with the density, mean atomic number, composition (%) or weight fraction, total atomic cross-section, crystal geometry and elemental packing of each molecule. It can be concluded that Ag 2 S was the superior attenuator between the sulphides under prediction, especially at higher energies. The Gamma Protection Efficiency (GPE, %) was also calculated for the gamma shielding subject based on the Linear Attenuation Coefficient (LAC) data presented in the Beer-Lamberts law: GPE% = (1-e^(-µx)) * 100, where the thickness was assumed. The GPE% increased with increasing thickness and decreased with increasing energy. Also, silver sulphide showed the highest GPE among the other tested materials. The GPE% of the thermal or fast neutrons was also calculated, where the increasing order was SnS, SnS 2 , ZnS, MoS 2 , As 2 S 3 , CuFeS 2 , FeS, CoS, and Ag 2 S for thermal neutrons and SnS 2 , SnS, MoS 2 , As 2 S 3 , ZnS, CuFeS 2 , FeS, Ag 2 S, and CoS for fast neutrons.

This chapter presents an overview of the room temperature ionic liquids (RTILs), their composition, synthesis and use in electrochemical investigations. The advantageous electrochemical properties of RTILs make them a useful alternative to conventional solvents/electrolytes for more ecofriendly, innovative and sustainable electrochemistry. A brief discussion about the electrochemical advantages, potential applications, practical concerns and future challenges in RTIL based electrochemical investigations and applications is presented in the current chapter.

The imperative advancement of gamma-ray shielding materials is pivotal for ensuring radioactive and nuclear safety. In this study, our objective was to ascertain key gamma ray shielding parameters, including the mass attenuation coefficient (μm), effective atomic number (Zeff), half-value layer (HVL), effective electronic density (Neff), mean free path (MFP), and exposure buildup factor (EBF), for four oxyanion complexes (CaMoO4, PbCrO4, PbMoO4, or CaWO4). These calculations were performed using Phy-X software within the photon interaction range of 0.015-15 MeV. The investigated ternary chromate, tungstate, and molybdate complexes with the molecular formula ABO4, where A = Ca or Pb and B = Mo, Cr, or W, exhibited an exponential decrease in μm with increasing photon energy in the low-energy region. Lead molybdate demonstrated the highest μm followed by PbCrO4, CaWO4, and CaMoO4, correlating with their respective mean atomic numbers and densities. The mean free path values followed the order of PbMoO4, PbCrO4, CaWO4, and CaMoO4, indicating superior shielding properties due to effective mediumphoton interactions. The HVL increased with rising photon energy, with the minimum HVL observed in the presence of lead, primarily attributed to the photoelectric effect. Zeff exhibited a decrease with diminishing mean atomic number and density, with PbMoO4 displaying the highest Zeff, signifying superior γ-ray shielding capability. The exposure buildup factor (EBF) highlighted the interference of photons by calcium compared to lead compounds. The controlled parameters at low and high energy exposures were attributed to the anion and cation properties of the ternary ABO4, respectively. Among the evaluated materials, PbMoO4 emerged as the most effective gamma shielding material in the context of nuclear safety.

Manipulation techniques of materials at nanoscale level have been pointed in the last decades as a promising tool to develop a new class of modified electrodes applicable in biosensors. Also, the high control of material properties is crucial to detect single events at molecular and atomic level. For instance, nanostructured thin films obtained by Langmuir-Blodgett (LB) and Layer-by-layer (LbL) techniques has been reported as an interesting approach to obtain more selective and sensitive modified electrodes and in addition to nanostructured materials are promising strategies for the fabrication of electrochemical biodevices. Thus, our main focus in this review paper is to show an overview on recent trends in the utilization of manipulation techniques applied to the development of electrochemical biosensors. Emphasis will be given in the utilization of different techniques utilized on the modification of electrodes to enhance electrochemical biosensing performance of enzyme-, protein-and DNA-based biosensors and nano-based electrochemical biosensors for diagnosis.

The two-step electrochemical reduction of tetrachloro-1,2-benzoquinone (chloranil), 2-methyl-1,2-benzoquinone (toluquinone), and 9,10-anthraquinone in two room-temperature ionic liquids is addressed by means of voltammetry on a platinum electrode. For the subsequent quinone/radical anion (Q/Q •-) and radical anion/ dianion (Q •-/Q 2-) redox reactions, the experimental data on formal potentials in 1-butyl-3-methylimidazolium tetrafluoroborate ([C 4 mim][BF 4 ]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([C 4 mim][PF 6 ]) and literature data for the same reactants in various aprotic molecular solvents are considered in the framework of a common potential sequence (Fc + /Fc scale) and compared with solvation energies computed at various levels. For the Q/Q •couple, the agreement appeared to be satisfactory when solvation is described at the polarized continuum model (PCM) level. In contrast, for the Q •-/Q 2couple, the account for specific solvation at the molecular level is crucial.

New solid-contact potentiometric sensors have been developed for hydrogen phosphate recognition on the basis of ionic liquids containing tetrasubstituted derivatives of thiacalix[4]arene in cone and 1,3-alternate conformations with trimethyl-and triethylammonium fragments at the lower rim substituents. The recognition of selected anions including carbonate, hydrogen phosphate, perchlorate, oxalate, picrate, and EDTA was conducted using electrochemical impedance spectroscopy with ferricyanide redox probe. For the potentiometric sensor assembling, the ionic liquids were stabilized by multiwalled carbon nanotubes and carbon black deposited on the glassy carbon electrode. The influence of support, steric factors and modification conditions on the sensor performance has been investigated. As was shown, potentiometric sensors developed make it possible to selectively determine hydrogen phosphate anion within the concentration range from 1 × 10 −2 to 1 × 10 −6 M and limit of detection of 2 × 10 −7 −1 × 10 −6 M with unbiased selectivity coefficients varied from 1.2 × 10 −1 to 1.0 × 10 −8 (carbonate, acetate, oxalate, succinate, glutharate, glycolate, and malonate anions).

Glass nanopore-based all-solid-state ion-selective electrodes (ISEs) have been developed to probe the distribution of ionic species at micro-or submicrometer-length scales, e.g., mapping of ion flux through micrometer-sized pores. The all-solid-state ISE was fabricated by sealing a conically etched platinum wire (d) 25-µm; radius of etched tip <10 nm) into a soda lime glass capillary. A Pt disk was exposed by gentle polishing the glass and the disk etched to form a conical pore of submicrometer dimension (radius <∼500 nm; depth <∼30 µm). Ag was electroplated on the Pt electrode in the pore and gently chloridated to obtain a AgCl/Ag layer within the pore. The AgCl/Ag layer-coated ISE was used as a highly selective Clprobe in scanning electrochemical microscope experiments to map the ion flux through a micropore. The same ISE was also used as the base transducer of the neutral carrier-doped solvent polymeric membrane. The optimized polymer membranes used for the glass nanoporebased all-solid-state ISE require a higher ratio of plasticizer/polymer (9/1) compared to those for conventional ISE (2/1). An ISE based on deposition of an IrO 2 layer at the base of a glass nanopore electrode exhibited a highly sensitive response (79.7 (2.3 mV/pH) to variations in pH and could be used for ∼3 weeks.

Over the past decade many works have focused on various aspects of the dynamics of liquids confined at the nanoscale such as e.g. water flow enhancement through carbon nanotubes (CNTs). Transport of room temperature ionic liquids (RTILs) through various nanochannels has also been explored and some conflicting findings about their translational dynamics have been reported. In this work, we focus on translational dynamics of RTILs confined in various CNTs. By means of molecular dynamics simulations we highlight a substantially enhanced diffusion of confined RTILs with an increase up to two orders of magnitude with respect to bulk-phase properties. This ultrafast diffusion of RTILs inside CNTs is shown to result from the combination of various factors such as low friction, molecular stacking, size, helicity, curvature and cooperative dynamics effects. Room Temperature Ionic Liquids (RTILs) are molten salts composed of large organic cations and inorganic or organic anions. This class of solvents has been widely studied over the past decades due to their important applications 1,2 associated with their unique properties (negligible vapor pressure, thermal stability, non-flammability, high ionic conductivity and wide electrochemical stability window). More recently, the confinement of RTILs at the nanoscale has gained much attention given their relevance to important industrial applications such as electrochemical double-layer capacitors (EDLCs) 1-5 and dye-sensitized solar cells (DSSCs) for solar energy conversion 6-8. RTILs have also been considered as potential candidates as additives in lubricants 9 and ionogels 10 for which immobilization of RTILs inside nanoporous systems (carbon nanotubes (CNTs) 11 , silica frameworks 12 …) is required. The macroscopic performance of nanoconfined RTILs is ruled by both their structural and dynamic properties at the nanoscale 13-15 , which are strongly modified with respect to the bulk phase. Understanding the behavior of RTILs under nanoconfinement is then critical for the rational design of EDLCs, DSSCs and ionogels with optimal properties. While structural and electrical properties have been largely investigated translational dynamics of confined RTILs remains controversial and this lack of knowledge strongly limits our understanding of confined RTILs behavior. Several numerical and theoretical works have focused on RTILs confined into cylindrical nanopores, such as CNTs 14,16-22 or silica materials 23-25 , and slit-like pores such as rutile slabs 26 or graphitic pores 13. Results from these studies suggest that both local RTIL structure and local dynamics of confined cations and anions are very complex and heterogeneous, depending strongly on the distance between ions and the pore wall. In addition to their tremendous physical properties, CNTs represent models of hydrophobic nanopores enabling to explore ultraconfinement effects on local structure and dynamics of liquids. In this context, some interesting properties were reported for various liquids confined into CNTs such as fast diffusion 21,27,28 , low friction 27,28 , superpermittivity 29 , local surdensity 21,27,29,30 , etc. Dynamics of confined RTILs remains unclear and is still a matter of debate. By means of molecular dynamics (MD) simulations Pinilla et al. evidenced a faster molecular motion of [dmim + ][Cl − ] confined between two parallel structureless walls, notably for ions located close to the walls 8. Using quasielastic neutron scattering Chathoth et al. obtained an enhanced diffusivity for [bmim + ][Tf 2 N − ] and [H 2 NC(dma) 2 ][BETI] confined into mesoporous carbons 31,32. Their results provided the first experimental observations of RTILs diffusing faster under confinement than in the bulk phase. Hung and coworkers reported MD simulations of varying amounts of [Emim + ][TFMSI − ] confined inside uncharged slit-like graphitic nanopores of different widths 13. The local dynamics of [Emim + ][TfMSI − ] was found heterogeneous and strongly dependent on the distance between ions and the pore walls. Dynamics of ions located in the center of a slit pore of 5.02 nm in width was found similar to that of the bulk RTIL. Recently, Li et al. carried out MD simulations of [C 4 mim + ][Tf 2 N − ] confined in silica and carbon mesopores and observed a slowdown in ion diffusion inside both mesopores compared with bulk values 23 .

Cyclic voltammetry was used to investigate the oxidation of 8-oxo-2'-deoxyguanosine (8-oxo-dG) on the glassy carbon (GC), platinum, gold and SnO 2 electrodes over a range of the sweep rate, 8-oxo-dG concentration and the solution pH. Reaction mechanism that is common to all these electrodes involves the two-electron two-proton charge transfer step followed by the irreversible chemical reaction(s). Rate of the charge transfer reaction decreases with the increasing solution pH (GC, Pt, Au), and depends on the nature of the electrode material following the sequence GC > Pt, Au >> SnO 2. These effects can be related to the degree of oxidation of the electrode surface (Pt, Au, SnO 2), or to the density of the active surface sites (GC). Any of these electrodes can be used for the fabrication of an amperometric detector for 8-oxo-dG .

Ion transfer voltammetry at a polarized hydrophobic room temperature ionic liquid (RTIL) membrane was used for evaluation of the diffusion coefficients and the standard Gibbs energies of ion transfer of the protonated antimuscarinic agents tolterodine (TOL), fesoterodine (FES), and their common metabolite 5-hydroxymethyl tolterodine (5-HMT), as well as for their determination in the aqueous samples and urine. An analysis of the pH effect provided the parameters characterizing their lipophilicity both in their ionic and neutral forms confirming a remarkably low lipophilicity of 5-HMT. The application of the ion transfer voltammetry for a monitoring of the enzymatic hydrolysis of FES to 5-HMT was

Breathomics is widely emerging as a strategy for non-invasive diagnosis of respiratory inflammation. In this study, we have evaluated the metabolic signals associated with Coronavirus (SARS COV-2), mainly the release of nitric oxide in breath. We have demonstrated the utility of a breath analyzerbased sensor platform for the detection of trace amounts of this target species. The sensor surface is modified with Room Temperature Ionic Liquid (RTIL) that allows faster diffusion of the target gas and can be used for gas sensing application. A low limit of detection (LOD) of 50 parts per billion has been achieved with a 95% confidence interval for detection of nitric oxide.. This inhouse designed sensor is incorporated into a breath analyzer system that displays enhanced sensitivity, specificity, linearity, and reproducibility for NO gas monitoring. The developed sensor platform can detect target concentrations of NO ranging from 50 to 250 ppb, using 1-Ethyl-3-methylimidazolium Tetrafluoroborate ([EMIM]BF 4) as RTIL and displays fast response time of 5 s, thereby allowing easy detection of the target gas species. The sensor successfully quantifies the diffusion current and charge modulations arising within the electrical double layer from the RTIL-NO interactions through DC-based chronoamperometry (CA). The subjects tested negative and positive are significantly different (p < 0.01). The prototype can potentially be used for human health monitoring and screening, especially during the pandemic due to its portability, small size, an embedded RTIL sensing element, integrability with a low-power microelectronic device, and an IoT interface. Coronavirus, a family member of single stranded RNA viruses consists with potent viral genome, covered by a bilayer lipidic envelope and a large number of peplomers or spikes on the surface, is currently considered the scariest health hazard worldwide with its potent ability to spread and infect human mankind never than before. There are many different variants of it, and most of their variants spread rapidly and cause infection at human respiratory tract, which ultimately leads to serious respiratory illness, resulting in extremely high morbidity and even death. The global COVID-19 pandemic is caused by the spread of severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) 1-4. Nearly 372 million people have tested positive worldwide and nearly 5.6 million people have lost their lives due to this deadly outbreak till February 2022. The virus spreads via airborne transmission, that is droplets, blood borne transmission and fecal-oral transmission 5. One of the important factors regarding rapid spread of this disease includes its general symptoms being confused with common flu. Scientists at the Centers for Disease Control (CDC) and World Health Organizations have identified common symptoms of this disease including dry cough, headache, difficulty breathing, weakness, and lack of smell and taste. Moreover, it has been found in some extreme cases, dyspnea and/or hypoxemia can occur a week after the appearance of the disease, accompanied by septic shock, acute respiratory distress syndrome (ARDS), and dysfunction of coagulation 6. These different modes exacerbated the rapid spread of the virus and made it highly difficult to control the spread. A person infected with the COVID-19 virus can display symptoms such as fever, cough, or shortness of breath that can be completely non-specific to one disease or can remain asymptomatic. Even during the incubation period of the virus, the person infected can still transmit the virus particles to others 7. This pandemic shows no sign of ending due to the recent mutations of the novel coronavirus 8. The only way to control the spread of this pandemic is via rapid diagnostic testing and tracing. The gold standard test for the diagnosis of COVID-19 is reverse transcription-polymerase chain reaction (RT-PCR) and quantitative

Ion and electron transfer reactions at the interface between a redox-active ionic liquid (IL), (ferrocenylmethyl)dodecyldimethylammonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (FcMD-DATFPB), and water were investigated by cyclic voltammetry (CV) using the FcMDDATFPB membrane cell. The redox-active IL was shown to exhibit the same ion selectivity as the structurally similar but redox-inactive tridodecylmethylammonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. Ion transfer potentials evaluated from CV measurements allowed establishing the scale of absolute potential differences for the interfacial oxidation of FcMDDA + with the aqueous redox species including IrCl 6 2− , Fe(CN) 6 3− , Mo(CN) 8 3− , ICl 2 − or IBr 2 −. In order to rationalize experimental data, the theory of CV was developed for an electron transfer at one membrane interface that is coupled with the ion transfer at the other membrane interface. Electron transfer mechanism was supported by the linear correlation between the reversible half-wave potentials of the electron transfer across the water IL interface and the standard electrode potentials for the aqueous redox couples. A notable difference between the formal electron transfer potentials for the water IL and water 1,2-dichloroethane interfaces pointed to strong ion-ion interactions within IL affecting the ion activity coefficient term.

Cyclic voltammetry was used to investigate the oxidation of 8-oxo-2'-deoxyguanosine (8-oxo-dG) on the glassy carbon (GC), platinum, gold and SnO 2 electrodes over a range of the sweep rate, 8-oxo-dG concentration and the solution pH. Reaction mechanism that is common to all these electrodes involves the two-electron two-proton charge transfer step followed by the irreversible chemical reaction(s). Rate of the charge transfer reaction decreases with the increasing solution pH (GC, Pt, Au), and depends on the nature of the electrode material following the sequence GC > Pt, Au >> SnO 2. These effects can be related to the degree of oxidation of the electrode surface (Pt, Au, SnO 2), or to the density of the active surface sites (GC). Any of these electrodes can be used for the fabrication of an amperometric detector for 8-oxo-dG .

An amperometric solid-state sensor for the detection of nitrogen oxide in air has been constructed using a gold minigrid indicator electrode, Pt/air reference and platinum counter electrodes in contact with a solid polymer electrolyte containing 9.6% PVC, 87.0% 2-nitrophenyl octyl ether and 3.4% tetrabutylammonium hexafluorophosphate. The stationary electric current corresponding to the NO, reduction at the indicator electrode at-0.3 V versus Pt/air electrode exhibited a linear dependence on the NO, concentration in the range 0.2 to 5.0 ppm, with a sensitivityof 21.7 nA ppm-' (at 54% relative humidity), a standard deviation of 3.3 nA at 1.06 ppm NO,, and a detection limit of 75 ppb. The time constant or time required to attain 90% of the steady-state response is 3.3 s or 14 s, respectively. The response decreases linearly with increasing relative humidity (RH) with a slope of 0.14 nA ppm-' per 1% RH. The sensor shows an excellent stability over one month.

Ion transfer voltammetry at a polarized hydrophobic room temperature ionic liquid (RTIL) membrane was used for evaluation of the diffusion coefficients and the standard Gibbs energies of ion transfer of the protonated antimuscarinic agents tolterodine (TOL), fesoterodine (FES), and their common metabolite 5-hydroxymethyl tolterodine (5-HMT), as well as for their determination in the aqueous samples and urine. An analysis of the pH effect provided the parameters characterizing their lipophilicity both in their ionic and neutral forms confirming a remarkably low lipophilicity of 5-HMT. The application of the ion transfer voltammetry for a monitoring of the enzymatic hydrolysis of FES to 5-HMT was

Speciation of copper in the abstraction of nano copper with a room temperature ionic liquid (RTIL) (1-butyl-3-methylimidazolium hexafluorophosphate [C 4 mim][PF 6 ]) has been studied by X-ray absorption near edge structural (XANES) and extended X-ray absorption fine structural (EXAFS) spectroscopies in the present work. The least-square fits of the XANES spectra suggest that nano CuO (79%) and Cu(II) complex (Cu(II)-IL) (21%) are the main copper species in the RTIL. The fitted EXAFS spectra show that the Cu-O (1st shell) bond distance is 2.08 Å with a coordination number (CN) of 2.6. In the second shells of copper, the average bond distance of Cu-Cu is 2.99 Å with a CN of 5.1.

The potential utility of room temperature ionic liquids as electrolytes in current electrochemical applications has been explored. Hence, the electrochemical behavior of [Ni(tmc)]Br2 complex at a glassy carbon electrode in the absence or in the presence of unsaturated halides in the ionic liquids, 1-ethyl-3-methylimidazolium ethylsulfate, [C2mim][C2SO4] and N,N,N-trimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2], has been examined by cyclic voltammetry. It was observed that [Ni(tmc)]2+ complex is reduced in a reversible one-electron step and the electrogenerated [Ni(tmc)]+ complex catalytically reduces the carbon-halogen bond of unsaturated halides. The potencial use of natural ionic conducting polymer matrixes was also investigated. Samples of natural macromolecules-based electrolytes with the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate, [C2mim][C2SO4], were prepared and characterized. The preliminary studies carried out with el...

The identification and transportation of trace explosive residues following the detonation of an explosive device or during an explosive related criminal investigation is a crucial yet often time consuming process. The ability to detect explosives at or near an explosion scene therefore offers considerable time advantages in the investigation. For this reason, the development of field-deployable portable analytical instruments is an active area of research. This review explores the potential use of electrochemical sensors for in-situ trace explosives detection. A key focus of this review article is the use of room temperature ionic liquids (RTILs) for the electrochemical detection of explosives. The review compares reaction mechanisms for the electrochemical reduction of TNT in aqueous solutions and in RTILs, before a discussion is made on recent work investigating explosives detection in aqueous, non-aqueous and RTIL-based samples. Finally, commentary is made on the anticipated future direction and challenges of this field.

An amperometric ascorbic acid selective sensor utilizing the transfer reaction of proton liberated from the dissociation of ascorbic acid in aqueous solution across an elliptic micro-hole water/ organic gel interface is demonstrated. This redox inactive sensing platform offers an alternative way for the detection of ascorbic acid to avoid a fouling effect which is one of the major concerns in redox based sensing systems. The detection principle is simply measuring the current change with respect to the assisted transfer of protons by a proton selective ionophore (e.g., ETH 1778) across the micro-hole interface between the water and the polyvinylchloride-2-nitrophenyloctylether gel phase. The assisted transfer reaction of protons generated from ascorbic acid across the polarized micro-hole interface was first characterized using cyclic voltammetry. An improved sensitivity for the quantitative analysis of ascorbic acid was achieved using differential pulse stripping voltammetry with a linear response ranging from 1 to 100 µM concentrations of ascorbic acid. As a demonstration, the developed sensor was applied for analyzing the content of vitamin-C in different types of commercial pharmaceutical tablets and syrups, and a satisfactory recovery from these samples were also obtained.

We present a new electrochemical system that combines paper-based sensing and ion-transfer voltammetry, bringing the latter a step closer toward point-of-care applications. Studies at the interface between two immiscible electrolyte solutions (ITIES) are often performed to detect redox-inactive species; unfortunately, due to the inherent instability of the interface, it is rather poorly explored outside specialized laboratories. Here, we address this limitation by combining a pen-like device containing the gelled organic phase with a papersupported aqueous phase. This combination makes the system more user-friendly, potentially low-cost, and easy to assemble. We show the applicability of the new cell to analyze both simple and ionophore-facilitated transfer of ions and proteins, preconcentration of species, and analysis of mixtures through combination with paper chromatography. The native ion content of the paper also enabled measurements without added electrolytes. Those studies could broaden the scope for the application of the label-free electrochemical detection of nonredox-active species at points-of-need.

In this study, total atomic cross-section (σta), total moleculer cross-section (σtm) total electronic cross-section (σte), effective atomic number (Zeff), effective electron density (Neff) and Kerma (K) were determined both experimentally and theoretically values for some iodine compounds. Experimental mass attenuation coefficient (µ/ρ) values for some iodine compounds were calculated with the data obtained from the test results. The theoretical mass attenuation coefficient values of these compounds were calculated with the WinXCOM data program. Also, we have performed the measurements for the calculations of experimental values mass attenuation coefficient using direct transmission experimental geometry. The transmission photon intensity of halogene iodine compounds were measured in a narrow beam experiment geometry was used 59.543 keV γ-ray from an 241Am radioactive source. The tranmissions spectra from iodine compounds were recorded with a Si (Li) detector having a resolution of ...

Application of tetraalkylammonium cation clathrate hydrates as electrolytes in interfacial electrochemistry has been presented. All experiments were performed in a wide temperature range, including liquid and solid electrolyte. It has been shown that the Autelectrolyte interface exhibits constant phase element behavior, with fractional exponent being between 0.7 and 1. No substantial temperature dependence of this parameter was noticed. For systems with fractional exponent close to unity, the temperature coefficient of the electric double layer capacitance is positive for all studied electrolytes. The electrode reaction of redox active ion added to tetraalkylammonium cation clathrate hydrates was studied, it has been concluded that at temperatures below the melting point of electrolyte, the motion of redox active ions is restricted to intergrain spaces of electrolyte. No substantial change of either interfacial parameters or apparent diffusion coefficient of redox active ion is observed at temperatures around the melting point of the studied electrolytes. This may suggest a similar structure of electrolyte near the electrode surface at temperatures below and above its melting point.

A comprehensive and consistent set of formulas is given for calculating the effective atomic number and electron density for all types of materials and for all photon energies greater than 1 keV. The formulas are derived from first principles using photon interaction cross sections of the constituent atoms. The theory is illustrated by calculations and experiments for molecules of medical and biological interest, glasses for radiation shielding, alloys, minerals and liquids.

An electrochemical system composed of two polarizable interfaces (the metallic electrode j water and water j ionic liquid interfaces), namely two-polarized-interface (TPI) technique, has been proposed to explore the ion transfer processes between water and moderately hydrophobic ionic liquids (W j mIL), typically 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C 8 mimC 1 C 1 N) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C 6 mimC 1 C 1 N). Within the classic four-electrode system, it is not likely that the ion transfer information at the W j mIL interface can be obtained due to an extremely narrow polarized potential window (ppw) caused by these moderately hydrophobic ionic components. In this article, we show that TPI technique has virtually eliminated the ppw limitation based on a controlling step of concentration polarization at the electrode j water interface. With the aid of this technique, the formal ion transfer potential differences between C 1 C 1 N À and C n mim + (n = 6, 8) were accurately determined for 356 mV and 420 mV at a corresponding interface (W j C 6 mimC 1 C 1 N and W j C 8 mimC 1 C 1 N). Besides, this technique is used to monitor electrochemical polarization at the two W j mIL systems, which exhibits an adaptable polarizability (i.e., a conversion from a nonpolarized interface to a polarized interface). Some of the typical anion transfers at the W j C 8 mimC 1 C 1 N interface have also been investigated, as they are particularly important for ion extraction. The experimental results indicate that this facile TPI technique offers a general avenue to explore ion transfer in multifarious biphasic systems.

Nanotechnology applications in technique, analytical chemistry, environmental chemistry and life science allows to change ours conception about possibilities of chemical technology. One of significant applications of nanotechnology is electrochemistry. In electrochemistry, applications of nanotechnology can be endless: from sensors for monitoring of traces (analytical signal /current/ –at level 10-12 -10-7 A) to power sources such as accumulators and fuel cells (current range from 10-7 up to 102-103 A). In general, dynamic electrical current range is of 14 orders. It should be underlined that in all the cases we have deal with 3-D Nano-structures of electrodes. R&D work in the field allows dramatically increasing sensitivity of sensors and efficiency of power sources in comparison to traditional bulk electrodes. One of main challenge of future is new energetics. Oil free, powerful and at the same time, ecological friendly energetic can change human&#39;s future. One of prospective i...

The applicability of ion exchange membranes is mainly defined by their permselectivity towards specific ions. For instance, the needed selectivity can be sought by modifying some of the components required for the preparation of such membranes. In this study, a new class of materials-trihexyl(tetradecyl)phosphonium based ionic liquids (ILs) were used to modify the properties of ion exchange membranes. We determined selectivity coefficients for iodide as model ion utilizing six phosphonium-based ILs and compared the selectivity with two classical plasticizers. The dielectric properties of membranes plasticized with ionic liquids and their response characteristics towards ten different anions were investigated using potentiometric and impedance measurements. In this large set of data, deviations of obtained selectivity coefficients from the well-established Hofmeister series were observed on many occasions thus indicating a multitude of applications for these ion-exchanging systems.

Many relevant questions in biology and medicine require both topography and chemical information with high spatial resolution. Several biological events that occur at the nanometer scale level need to be investigated in physiological conditions. In this regard Atomic Force Microscopy (AFM) is one of the most powerful tools for label-free nanoscale characterization of biological samples in liquid environment. Recently, the coupling of Raman spectroscopy to scanning probe microscopies has opened new perspectives on this subject; however, the coupling of quality AFM spectroscopy with Raman spectroscopy in the same probe is not trivial. In this work we report about the AFM capabilities of an advanced high-resolution probe that has been previously nanofabricated by our group for coupling with Raman spectroscopy applications. We investigate its use for liquid AFM measurements on biological model samples like lipid bilayers, amyloid fibrils, and titin proteins. We demonstrate topography resolution down to nanometer level, force measurement and stable imaging capability. We also discuss about its potential as nanoscale chemical probe in liquid phase.

Graphite rods coated with poly(dimethyldiallylammonium chloride), poly(DMDAAC), and subjected to immobilization by 7-irradiation have been shown to respond linearly to dissolved oxygen concentration. The oxygen is detected electrochemically by reduction at a potential of-0.40 V versus Ag/AgCI. The concentration range of linearity investigated is 1.4 to 9.3 ppm. The polymer-coated electrode has a sensitivity of 12.5 taA cm-2 ppm-', a detection limit of 1.4 ppm and a response time of 5 min or less. Poly(DMDAAC) also provides the electrode surface with some protection against adsorbing species during the measurement. Further, poly(DMDAAC) can function as the electrolyte in a solid-state cell and allows electrochemical measurements to be made in air in the absence of a supporting electrolyte solution. The response to oxygen concentration in the surrounding atmosphere is shown.

A fuel cell based amperometric H 2 sensor with pulsed electrodeposited electrodes has been developed and tested for its performance. Nafion, a commercial proton exchange membrane was used as electrolyte in the sensor. Platinum (Pt) deposited gas diffusion electrode (GDE) based sensing and counter electrodes were prepared by electrodeposition and pulsed electrodeposition methods using 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid electrolyte. Prior to the electrodeposition, the electrodeposition behaviour of Pt on GDE was studied by cyclic voltammetry, chronoamperometry and chronopotentiometry. The deposition potential of Pt was obtained from cyclic voltammogram. The nucleation and growth behaviour of Pt were examined by chronopotentiom-etry and chronoamperometry. Electrodeposition and pulsed electrodeposition of Pt on GDE were carried out under the optimized conditions. The prepared electrodes were characterized by field emission scanning electron microscope and gracing incidence X-ray diffraction. In order to compare the sensor performance, Nafion based amperometric hydrogen sensors were made with both electrodeposited and pulsed electrodeposited Pt on GDE electrodes. The assembled amperometric H 2 sensors were tested in the dynamic range of 1-4% of H 2 /Ar. Pulsed electrodeposited Pt on GDE sensor showed higher sensitivity and better response time than the electrodeposited Pt on GDE sensor.

Environmental monitoring has been one of the key to provide better safety measure in various sectors of life. The most famously featured technology in this area is the gas detecting system. It serves not only in an early-warning application, but also a continuous mean to provide background check of the atmospheric status of a specific area ranges. According to their principals, gas sensors can be separated into two categories; the conductive metal-oxides and the electrochemical-type, with the latter gaining more recognition over the last decade as the future standard component in any gas sensing apparatus. Within this article, the whole concept of an electrochemical gas sensor will be presented, including the basic science and the basic electronical engineering that runs the device. The main concern will be fallen onto a specific amperometric-type sensor as the most common electrochemical sensor in the market. Ultimately, since there are multiple parts that comprise a single electrochemical sensor, a special section will be written within this article to show the array of materials that are responsible to the sensing capabilities of the sensor, particularly in the area of sensitivity and selectivity of gases.

88.0 keV photon energies. The samples were irradiated with 109 Cd and 241 Am radioactive point sources using transmission arrangement. The X-and c-rays were counted by a Si (Li) detector with resolution of 160 eV at 5.9 keV. Total atomic and electronic cross-sections (r t and r e), effective atomic numbers (Z eff) and electron densities (N el) were determined using the obtained l/q values for the investigated crystals.

Cyclic voltammetry was used to investigate the oxidation of 8-oxo-2'-deoxyguanosine (8-oxo-dG) on the glassy carbon (GC), platinum, gold and SnO 2 electrodes over a range of the sweep rate, 8-oxo-dG concentration and the solution pH. Reaction mechanism that is common to all these electrodes involves the two-electron two-proton charge transfer step followed by the irreversible chemical reaction(s). Rate of the charge transfer reaction decreases with the increasing solution pH (GC, Pt, Au), and depends on the nature of the electrode material following the sequence GC > Pt, Au >> SnO 2. These effects can be related to the degree of oxidation of the electrode surface (Pt, Au, SnO 2), or to the density of the active surface sites (GC). Any of these electrodes can be used for the fabrication of an amperometric detector for 8-oxo-dG .

Chlorine gas is a greenish-yellow gas that is one of the most utilized gases in numerous industrial fields. It has been categorized as a choking agent that can threaten human, animal, and environmental safety. Currently, development of highly sensitive, selective, and precise chlorine sensors receives much attention. This review focuses on several sensing techniques used for chlorine gas and free chlorine in water. The fundamental working principles, as well as the sensing mechanisms of chlorine detection covering spectrophotometric, electrochemical, and optical techniques, are described. A comparison of various sensing materials is also discussed. Finally, an overview of the future improvements needed of high-performance chlorine sensors was suggested.

The construction and performance characteristics of ionselective micro-electrodes for acetylcholine and choline based on their complexes with dipicrylamine are described. The micro-electrodes show near-Nemstian response over ranges of about 5 X 10-5-'101 M. The selectivity of these micro-electrodes relative to a number of amino acids, inorganic ions, neurotransmitters, and drugs is reported. Naturally occurring components of neural tissue did not interfere strongly, while many choline&c drugs (arecholine, carbachol, atropine, scopolamine, and others) interfered. The effect of different nitroaromatic solvents on selectivity is described. Measurements in vivo are possible.

The technological utility of biomolecules (e.g. proteins, enzymes and DNA) can be significantly enhanced by combining them with ionic liquids (ILs)-potentially attractive "green" and "designer" solvents-rather than using in conventional organic solvents or water. In recent years, ILs have been used as solvents, cosolvents, and reagents for biocatalysis, biotransformation, protein preservation and stabilization, DNA solubilization and stabilization, and other biomolecule-based applications. Using ILs can dramatically enhance the structural and chemical stability of proteins, DNA, and enzymes. This article reviews the recent technological developments of ILs in protein-, enzyme-, and DNA-based applications. We discuss the different routes to increase biomolecule stability and activity in ILs, and the design of biomolecule-friendly ILs that can dissolve biomolecules with minimum alteration to their structure. This information will be helpful to design ILbased processes in biotechnology and the biological sciences that can serve as novel and selective processes for enzymatic reactions, protein and DNA stability, and other biomolecule-based applications.

Subnanomolar limits of detection (LODs) are obtained for stripping voltammetry based on ion transfer at the interface between the aqueous sample and the thin polymeric membrane supported with a solid electrode. It has been predicted theoretically that a lower LOD can be obtained for a more lipophilic analyte ion, which can be preconcentrated at a higher equilibrium concentration in the solid-supported thin polymeric membrane to enhance a stripping current response. This study is the first to experimentally confirm the general theoretical prediction for both cationic and anionic analytes. Proof-of-concept experiments demonstrate that a subnanomolar LOD of (8 (4) × 10-11 M tetrapropylammonium is significantly lower than a LOD of less lipophilic tetraethylammonium. Importantly, stripping voltammetry of the cationic analytes is enabled by newly introducing an oxidatively doped poly(3,4-ethylenedioxythiophene) film as the intermediate layer between a plasticized poly(vinyl chloride) membrane and a Au electrode. On the other hand, an undoped poly(3-octylthiophene) film is used as an intermediate layer for voltammetric detection of a lipophilic inorganic anion, hexafluoroarsenate, an arsenical biocide found recently in wastewater. A LOD of (9 (2) × 10-11 M hexafluoroarsenate thus obtained by ion-transfer stripping voltammetry is comparable to a LOD of 80 pM by inductively coupled plasma mass spectrometry with anion-exchange chromatography. Great sensitivity for a lipophilic ion is potentially useful for environmental analysis because high lipophilicity of an ion is relevant to its bioaccumulation and toxicity.

Determination of the mass attenuation coefficient, l/q, the effective atomic number, Z eff , and the effective electron number, N eff , is very important in the fields of nuclear diagnostics, radiation protection, nuclear medicine and radiation dosimetry. In this work, the Direct-Z eff software was developed for the computation of the mass attenuation coefficient, the effective atomic number and the effective electron number per unit mass in the energy range 1 keV-100 GeV. The values of the Z eff , N eff and l/q can be determined for total photon interaction with and without coherent interaction as well as partial photon interactions such as coherent scattering, incoherent scattering, photoelectric absorption and pair production by using the Direct-Z eff software. The accuracy of the Direct-Z eff software has been demonstrated by comparing the calculated data and the experimental values for the various materials. The Direct-Z eff software can be freely obtained by contacting with the authors.

The electrochemical behavior of a platinum electrode in a set of 1-alkyl ether (and 1-alkyl)-3-methylimidazolium room-temperature ionic liquids (RTILs) 1-3 ([C x O y Mim] + [Anion] − or [C x Mim] + [Anion] − , where Mim = 3-methylimidazolium; C x O y = 1-alkyl ether; C 7 O 3 =-(CH 2) 2 O(CH 2) 2 O(CH 2) 2 OCH 3 ; C 3 O 1 =-(CH 2) 2 OCH 3 ; C x = 1-alkyl; C 10 = C 10 H 21 ; C 4 = C 4 H 9 ; and Anion ½ À ¼ H 3 CSO À 3 ; BF À 4 ; or PF À 6) was studied by cyclic voltammetry and electrical conductivity. This complementary set of imidazolium RTILs allowed us to explore the effect of the imidazolium cation and the counter-ion, both of which affected the electrochemical window of these RTILs. Various electrochemical events with low current values were observed, which diminished the electrochemical windows. Interestingly, RTILs 2b [1-(2-methoxyethyl)-3-methylimi-dazolium tetrafluoroborate] and 2d [1-butyl-3-methylimidazolium tetrafluoroborate] showed quasireversible charge transfer processes. The length of the functional group attached to the imidazolium cation was shown to be of great influence as larger electrochemical windows, as well as lower electrical conductivities, were obtained with the longer C 7 O 3 and C 10 functional groups. The largest electrochemical window of 2.0 V was achieved with RTIL 2c, 1-decyl-3-methylimidazolium tetrafluoroborate.

Cyclic voltammetry measurements using a platinum electrode were performed to study the effect of water when added to the imidazolium room-temperature ionic liquids (RTILs) 1 [C 7 O 3 MIm][Mes] and 2 [C 3 O 1 MIm][Mes]. The addition of a very small amount of water to RTIL 1 resulted in diminished cathodic current values. An even more pronounced effect was observed with RTIL 2 and all charge transfer processes were extremely reduced. This inhibition of the charge transfer processes suggests the formation of new species, due to a reaction between water and the RTILs, that adsorbs on the electrode surface.

Speciation and possible reaction paths of nanosize copper pollutants extracted with a RTIL (room-temperature ionic liquid ([C 4 mim][PF 6 ], 1-butyl-3-methylimidazolium hexafluorophosphate)) have been studied in the present work. Experimentally, in a very short contact time (2 min), 80-95% of nanosize CuO as well as other forms of copper (such as nanosize Cu, Cu 2+ , or Cu(II) (ads) (in the channels of MCM-41)) in the samples could be extracted into the RTIL. The main copper species extracted in the RTIL as observed by XANES (X-ray absorption near edge structure) were Cu(II). Existence of Cu-N bondings with coordination numbers (CNs) of 3-4 for copper extracted in the RTIL was found by EXAFS (extended X-ray absorption fine structural) spectroscopy. Interestingly, chelation of Cu(II) with 1-methylimidazole (MIm) in the RTIL during extraction was also observed by 1 H NMR (nuclear magnetic resonance). At least two possible reaction paths for the rapid extraction of nanosize copper pollutants with the RTIL might occur: (1) an enhanced dissolution of nanosize CuO (to form Cu 2+ ) and (2) formation of [Cu(MIm) 4 (H 2 O) 2 ] 2+ that acted as a carrier of copper into the RTIL matrix.

The effective atomic numbers (Z eff) and effective electron density (N e) for three different steels have been determined via the mass attenuation coefficients (l/q). The mass attenuation coefficients have been calculated at the photon energy range of 1 keV-1 GeV and measured at the photon energies of 662, 1173 and 1332 keV. The measurement has been performed using a gamma spectrometer that contains a NaI(Tl) detector connected to Multi-Channel-Analyzer (MCA). The measured results of effective atomic numbers (Z eff) and effective electron density (N e) were found to be in good agreement with the calculations.

Cyclic voltammetry is used to study the transfer of a series of cations and anions across a room-temperature ionic liquid membrane composed of tridodecylmethylammonium cation and tetrakis[3,5-bis(trifluoromethyl) phenyl]borate anion. It is shown that the addition of water-soluble crown ether (e.g. 18-crown-6) to the aqueous phase makes it possible to distinguish the voltammetric responses of alkali and alkaline earth metal cations. The determination of low concentrations of K þ (0.05-0.3 mM) in the presence of an excess of Mg 2þ (1 mM) in water is demonstrated as a model application of an amperometric ion-selective electrode for K þ .

The focus of this article is to describe a simple-to-use, disposable sensor suitable for the rapid determination of pollutants in aqueous media, utilising a novel sonochemical microelectrode fabrication technique. The use of screen-printing, electrochemical and sonochemical methods allows the production of microelectrode arrays capable of stir- independent determination of chlorine in water. These arrays permit the simultaneous measurement of free and total chlorine at concentrations between 0-20 ppm. Developments leading to production on a mass scale will be briefly discussed. A further system incorporating enzyme containing conductive polymers to give microelectrode arrays capable of detection of ultra-low levels of organophosphate pesticides will also be described. Acetylcholine esterase could be entrapped within conductive polyaniline protrusions and the effects of pesticides on its activity determined. Ultra low concentrations of pesticide were found to reduce the enzymes activ...