The development of sensitive, selective, and reliable gaseous hydrogen peroxide (H2O2) sensors operating at room temperature still represents a remaining challenge. In this work, we have investigated ...and combined the advantageous properties of a two-dimensional Ti3C2T x MXene material that exhibits a large specific surface area and high surface activity, with favorable conducting and stabilizing properties of chitosan. The MXene–chitosan membrane was deposited on the ferrocyanide-modified screen-printed working carbon electrode, followed by applying poly(acrylic acid) as an electrolyte and accumulation medium for gaseous H2O2. The sensor showed highly sensitive and selective electroanalytical performance for detecting trace concentrations of gaseous H2O2 with a very low detection limit of 4 μg m–3 (4 ppbv), linear response in the studied concentration range of 0.5–30.0 mg m–3, and good reproducibility with an RSD of 1.3%. The applicability of the sensor was demonstrated by point-of-interest detection of gaseous H2O2 during the real hair bleaching process with a 9 and 12% H2O2 solution.
Rapid and reliable immunosensing is undoubtedly one of the priorities in the efficient management and combat against a pandemic, as society has experienced with the SARS-CoV-2 outbreak; simple and ...cost-effective sensing strategies are at the forefront of these efforts. In this regard, 2D-layered MXenes hold great potential for electrochemical biosensing due to their attractive physicochemical properties. Herein, we present a V2CT x MXene-based sensing layer as an integral part of a label-free immunosensor for sensitive and selective detection of the SARS-CoV-2 spike protein. The sensor was fabricated on a supporting screen-printed carbon electrode using Nafion as an immobilizing agent for MXene and glutaraldehyde, the latter enabling effective binding of protein A for further site-oriented immobilization of anti-SARS-CoV-2 antibodies. A thorough structural analysis of the sensor architecture was carried out, and several key parameters affecting the fabrication and analytical performance of the immunosensor were investigated and optimized. The immunosensor showed excellent electroanalytical performance in combination with an impedimetric approach and exhibited a low detection limit of only 45 fM SARS-CoV-2 spike protein. Its practical applicability was successfully demonstrated by measuring the spike protein in a spiked artificial nasopharyngeal fluid sample.
In this proof-of-concept study, we used laser-pyrolyzed paper as the supporting electrodes for the swift, impedimetric, and enzymeless detection of
d
-glucose by the means of molecularly imprinted ...polymer. Molecular imprinting of monomer 3-amino-4-hydroxybenzoic acid was performed by electrochemical polymerization in the presence of
d
-glucose as a template molecule, followed by the template removal process via cyclic voltammetry in PBS (pH = 7.4). The analytical capacitance signal was extracted from the raw electrochemical impedance spectra recorded after only 60 s of incubation with the analyte. The electrodes were characterized by Raman spectroscopy and scanning electron microscopy to disclose their structural and morphological properties, revealing the presence of nanographene of high porosity. The analytical performance was investigated in the clinically relevant range of 0–30 mmol dm
−3
, which demonstrated good linearity (
r
2
= 0.97), decent limit of detection (1.77 mmol dm
−3
), an excellent selectivity (
ɑ
= 1.38–3.73), and good reproducibility (5.0%).
Graphical abstract
This paper shows that weak legal and political institutions and high macroeconomic volatility shorten the maturity of cross-border bank lending. Although these results are confirmed in the previous ...literature, this paper uses a broader panel data set of 135 countries from 1983 to 2012. Data also suggest new finding that the maturity of international bank credit and per capita GDP are positively correlated. The share of debt incurred by banks shortens the maturity, while the share of debt incurred by governments lengthen the maturity of cross-border credit. Our results are robust after we control for potential endogeneity.
Lignins and lignin-derived compounds are known to have antibacterial properties. The wound healing agents in the form of dressings produce faster skin repair and decrease pain in patients. In order ...to create an efficient antimicrobial agent in the form of dressing in the treatment of chronic wounds, a composite hydrogel of bacterial cellulose (BC) and dehydrogenative polymer of coniferyl alcohol (DHP), BC-DHP, was designed. Novel composite showed inhibitory or bactericidal effects against selected pathogenic bacteria, including clinically isolated ones. The highest release rate of DHP was in the first hour, while after 24 h there was still slow release of small amounts of DHP from BC-DHP during 72 h monitoring. High-performance liquid chromatography coupled with mass-spectrometry showed that BC-DHP releases DHP oligomers, which are proposed to be antimicrobially active DHP fractions. Scanning electron microscopy and atomic force microscopy micrographs proved a dose-dependent interaction of DHP with BC, which resulted in a decrease of the pore number and size in the cellulose membrane. The Fourier-transform infrared absorption spectra of the BC-DHP showed that DHP was partly bound to the BC matrix. The swelling and crystallinity degree were dose-dependent. All obtained results confirmed BC-DHP composite as a promising hydrogel for wounds healing.
•Novel composite BC-DHP in form of dressing showed inhibitory/bactericidal effect.•BC-DHP showed highest release of the active substance during the first 24 h.•Released active compounds were oligomers of coniferyl alcohol.•High swellability of hydrogel confirmed its potential role in chronic wound healing.
Copper electrodes exhibit interesting characteristics for application in electrochemical stripping analysis and represent another alternative to their mercury counterparts. In this work, we studied ...different types of copper-based electrodes for anodic stripping voltammetric detection of trace metal ions. We investigated copper film (CuFE), and bulk copper electrodes, such as in-situ and ex-situ prepared CuFEs using glassy carbon and screen-printed carbon supporting electrodes, a bulk copper disk and screen-printed copper electrode, and a copper wire as the simplest, inexpensive, and readily available analog. For studying their electroanalytical performances, low concentrations (μg L−1) of Cd(II) and Pb(II) were used as model ions. We examined and optimized several key parameters affecting the preparation and functioning of copper electrodes, such as the composition of the measurement solution, copper concentration for in-situ and ex-situ preparation of CuFE, deposition potential, deposition time, etc. Most of the tested copper electrodes showed favorable stripping voltammetric performances, particularly the CuFE ex-situ prepared on a glassy carbon electrode and the CuFE in-situ prepared on a screen-printed carbon substrate. Notably, a copper wire revealed an excellent electroanalytical operation with a limit of detection of 0.6 μg L−1 for Pb(II) and 1.8 μg L−1 for Cd(II). The practical applicability of a copper electrode was tested by measuring a real tap water sample.
Four novel polymeric iron(III) complexes with 2,2?-bipyridine (bipy) and
different aromatic polycarboxylato ligands as anions of phthalic (pht),
isophthalic (ipht), terephthalic (tpht) and ...pyromellitic (pyr) acid were
synthesized by ligand exchange reaction. The complexes were characterized by
elemental and TG/DSC analysis, FTIR and diffuse reflectance UV-VIS-NIR
spectroscopy and magnetic susceptibility measurements. Based on analytical
and spectral data the formulae of the complexes are {Fe4(bipy)2
(H2O)2(OH)6(pht)3?2H2O}n (1), {Fe4(bipy)2(Hipht)2(ipht)2(OH)6?4H2O}n (2),
{Fe4(bipy)2(Htpht)2(OH)6(tpht)2?4H2O}n (3) and {Fe4(bipy)(H2O)8(OH)4
(pyr)2?H2O}n (4). All complexes are red brown and low-spin with a distorted
octahedral geometry and FeO6 or FeN2O4 chromophore. Polycarboxylato ligands
have a bridging role in all cases, whereas monodentate COO groups are present
in 2 and 3, bridging and chelate COO groups are established in 1 and 4. The
thermal behaviour of 1-4 was investigated in detail and the molar dehydration
enthalpies were calculated. According to the all those results, the
structural formulae of the complexes 1-4 were proposed.
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