Thionine Molecules Research Articles

Spectral properties of hybrid associates of colloidal quantum dots Zn0.5Cd0.5S, europium tenoyltrifluoroacetonate and methylene blue

Hybrid associates formed from colloidal Zn0.5Cd0.5S quantum dots, passivated with thioglycolic acid, europium tenoyltrioteracetonate and methylene blue molecules, absorption, luminescence, IR and time-resolved spectroscopy technique are studied. The shift of the IR absorption bands of COO- and C=O groups of thioglycolic acid and europium thenoyltrifluoroacetonate has been detected. An increase in the efficiency of excitation of europium luminescence and a simultaneous increase lifetime of its luminescence upon adsorption on Zn0.5Cd0.5S quantum dots were found. Addition of methylene blue (thionine) molecules leads to quenching of the trap state luminescence of Zn0.5Cd0.5S and intracentric luminescence of Eu3+. A conclusion about the adsorption of Eu3+ on the surface of Zn0.5Cd0.5S quantum dots and the nonradiative energy transfer to methylene blue molecules was made.

Förster resonance energy transfer in hybrid associates of colloidal Ag2S quantum dots with thionine molecules

Nonradiative resonance energy transfer in hydrophilic hybrid associates of thionine molecules (TH+) with colloidal Ag2S quantum dots (QDs) with average diameter of 3.5 nm was studied. Photoluminescence spectra and its decay shown that for these systems the supplemental photosensitization of recombination luminescence of Ag2S QDs (1200 nm) from the region of TH+ fluorescence (618 nm) is possible. It was found that the average lifetime of TH+ molecules luminescence is shortened during their association with Ag2S QDs. Approximation of luminescence decay by stretched exponent with value of parameter β = 0.5 indicates on the inductive-resonance dipole-dipole (Forster) mechanism of nonradiative energy transfer (FRET). The efficiency of FRET was 0.29–0.41.

Sensitive determination of sialic acid expression on living cells by using an ITO electrode modified with graphene, gold nanoparticles and thionine for triple signal amplification

The authors demonstrate a multivalent recognition and triple signal amplification strategy for amperometric cytosensing and dynamic evaluation of cell surface sialic acid (SA). The strategy is based on the use of (a) graphene oxide functionalized with 3-aminophenylboronic acid (APBA-CG) for cell capture, and (b) of Sambucus nigra agglutinin and thionine conjugated to gold nanoparticles (SNA-AuNP-Th) acting as a nanoprobe. The use of APBA-CG accelerates electron transfer and warrant a large surface area for cell capture. The AuNPs, in turn, nanoprobe provide an effective matrix for mass loading of thionine molecules and thus dramatically improve sensitivity. The results obtained with the biosensor demonstrate that sialic acid is strongly expressed levels in cancer cells compared to normal ones. The cytosensor was applied to the detection of HepG2 cells. Best operated at a working voltage of typically 0.42 V vs. Ag/AgCl, it displays a wide linear range (that extends from 1.0 × 102 to 1.0 × 107 cells per mL and a low detection limit (50 cells per mL)). The method was successfully applied dynamic monitoring of the changes in cell surface SA expression in response to the addition of the enzyme sialidase. In our perception, the SNA-based biosensor represents a viable tool to study SA-related biological processes and for diagnosis and treatment of early stages of cancer.

Enhancement of Luminescence of Colloidal Ag2S Quantum Dots by Thionine Molecules

Enhancement of IR luminescence (1205 nm) of colloidal Ag2S quantum dots (QDs) with an average size of 2.5 ± 0.3 nm was detected upon excitation in the absorption band of thionine dye molecules (530–610 nm). It is found that the observed effect occurs during a hybrid association of Ag2S QDs with monomers of the cationic thionine (Th + ) molecule. It is concluded that the photosensitization of IR luminescence of colloidal Ag2S QDs is realized due to a resonance nonradiative transfer of electronic excitation energy directly to the centers of radiative recombination from the excited Th + molecules.

Molybdenum carbide nanotubes: a novel multifunctional material for label-free electrochemical immunosensing.

Herein, a multifunctional nanoarchitecture has been developed by integrating well-crystalline molybdenum carbide (Mo2C) nanotubes and an electrochemical indicator - thionin (TH). The Mo2C nanotubes were synthesized through the self-degradable template method and high-temperature calcination, and their structure and morphology were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Due to the high electrocatalytic properties, excellent conductivity and highly active surface area of Mo2C nanotubes, the Mo2C-based material was used as a nanocarrier to load TH molecules for the development of a label-free electrochemical immunosensor for α-fetoprotein (AFP) detection. The decorated TH probe on the Mo2C nanotubes not only acted as a bridging molecule to effectively capture and immobilize primary anti-AFP on the Mo2C nanotubes, but also acted as a signal indicator for the detection of AFP. The proposed immunosensor exhibited excellent selectivity (with a detection limit of 3 pg mL(-1)), high stability and good reproducibility by combining the unique structure and features of the Mo2C nanotubes. Furthermore, this sensing platform was finally used for the detection of AFP in human serum with satisfactory results. Therefore, the Mo2C nanotubes can be considered as a candidate carbon material for fabrication of simple, label-free and ultrasensitive electrochemical sensors, broadening the application of this material.

Homogeneous electrochemical detection of ochratoxin A in foodstuff using aptamer–graphene oxide nanosheets and DNase I-based target recycling reaction

A simple and feasible homogeneous electrochemical sensing protocol was developed for the detection of ochratoxin A (OTA) in foodstuff on the immobilization-free aptamer–graphene oxide nanosheets coupling with DNase I-based cycling signal amplification. Thionine-labeled OTA aptamers were attached to the surface of nanosheets because of the strong noncovalent binding of graphene oxide nanosheets with nucleobases and aromatic compounds. The electronic signal was acquired via negatively charged screen-printed carbon electrode (SPCE) toward free thionine molecules. Initially, the formed thionine–aptamer/graphene nanocomposites were suspended in the detection solution and far away from the electrode, thereby resulting in a weak electronic signal. Upon addition of target OTA, the analyte reacted with the aptamer and caused the dissociation of thionine–aptamer from the graphene oxide nanosheets. The newly formed thionine–aptamer/OTA could be readily cleaved by DNase I and released target OTA, which could retrigger thionine–aptamer/graphene nanocomposites with target recycling to generate numerous free thionine molecules. Free thionine molecules were captured by negatively charged SPCE, each of which could produce an electrochemical signal within the applied potentials. Under optimal conditions, graphene-based aptasensing platform could exhibit good electrochemical responses for the detection of OTA at a concentration as low as 5.6pg/mL. The reproducibility, precision and selectivity of the system were acceptable. Importantly, the method accuracy was comparable with commercialized OTA ELISA kit when using for quantitative monitoring of contaminated wheat samples.

Simple and sensitive detection of aflatoxin B1 within five minute using a non-conventional competitive immunosensing mode.

A novel competitive-type immunosensing strategy based on target-induced displacement reaction with antibody-functionalized mesoporous carbon (MSC) nanoparticles was designed for sensitive and rapid electrochemical detection of aflatoxin B1 (AFB1, used as a model) on the Nafion-functionalized sensing interface. Electroactive thionine molecules were initially decorated to the mesoporous carbon, and polyclonal anti-AFB1 antibody was then covalently conjugated to the nanostructures. The immunosensor was simply prepared via the electrostatic interaction between negatively charged Nafion film and positively charged anti-AFB1 antibody accompanying the nanostructures. The electrochemical signal originated from the carried thionine to mesoporous carbon. Upon target AFB1 introduction, the analyte reacted with the labeled anti-AFB1 antibody on the MSC based on specific antigen-antibody reaction and induced the dissociation of thionine-MSN nanostructures from the sensing interface, thus decreasing the cathodic current of the carried thionine molecules. Under optimal conditions, the immunosensor exhibited good electrochemical responses for determination of target AFB1 at a concentration as low as 3.0 pg mL(-1) (3.0 ppt). Importantly, the non-conventional sensing system provides a promising immunosensing strategy for rapid screening of small molecules because of its simplicity, low cost and sensitivity without the needs of sample separation and washing step.

Highly sensitive voltammetric detection of DNA hybridization in sandwich format using thionine-capped gold nanoparticle/reporter DNA conjugates as signal tags

A highly sensitive sandwich DNA detection method based on voltammetric detection of thionine-capped gold nanoparticle (AuNP)/reporter DNA conjugate tags on gold particle-modified screen-printed carbon electrode (SPCE) was developed. The SPCE was modified with gold particle by electrodeposition of gold on SPCE surface. The DNA sensor was prepared by self-assembly of a thiolated DNA probe on gold particle-modified SPCEs. The sandwich-type system was formed by specific recognition of biosensor surface-confined probe DNA to target DNA, followed by attachment of thionine-capped AuNPs/reporter DNA conjugates. The biosensor is very sensitive because of the large number of electroactive thionine molecules in the thionine-capped AuNPs/reporter DNA conjugates. Under optimal conditions, the dynamic detection range of target DNA was from 1.0 × 10−16 to 1.0 × 10−14 mol L−1, and the detection limit was 0.5 × 10−16 mol L−1. The DNA sensor exhibited selectivity against single-base mismatched DNA.

Highly sensitive detection of DNA using an electrochemical DNA sensor with thionine-capped DNA/gold nanoparticle conjugates as signal tags

A highly sensitive electrochemical DNA (E-DNA) sensor based on the voltammetric detection of thionine, which was capped on diblock DNA/gold nanoparticle (DiDNA/AuNP) conjugates, on a gold electrode was developed. The E-DNA sensor was prepared through the self-assembly of a 3′-end thiolated probe DNA (PDNA) on a gold electrode followed by the hybridization of thionine-capped DiDNA/AuNP conjugates to the 5′-end of the PDNA. The thionine-capped DiDNA/AuNP conjugate was acted as a tag. In the absence of the target DNA, the flexible single-stranded PDNA supports an efficient contact between tag and electrode, ensuring high current of the E-DNA sensor. Upon hybridization, a rigid probe-target duplex is formed, which pushes the tag away from the electrode and increases the distance between the tag and the electrode, thereby decreasing the current of the E-DNA sensor. The analytical method based on this concept is highly sensitive because the thionine-capped DiDNA/AuNP conjugate contains a large number of electroactive thionine molecules. Under optimal conditions, the dynamic detection range of the target DNA was from 1.0pM to 100pM, and the detection limit was 0.5pM. The DNA sensor also exhibited selectivity against single-base mismatched DNA.

Non-enzymatic detection of hydrogen peroxide using a functionalized three-dimensional graphene electrode

A novel three-dimensional (3D) electrochemical sensor was developed for highly sensitive detection of hydrogen peroxide (H2O2). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the electrode scaffold. Using in-situ polymerized polydopamine as the linker, the 3D electrode was functionalized with thionine molecules which can efficiently mediate the reduction of H2O2 at close proximity to the electrode surface. Such stable non-enzymatic sensor is able to detect H2O2 with a wide linear range (0.4 to 660μM), high sensitivity (169.7μAmM−1), low detection limit (80nM), and fast response (reaching 95% of the steady current within 3s). Furthermore, this sensor was used for real-time detection of dynamic release of H2O2 from live cancer cells in response to a pro-inflammatory stimulant.

Nanogold-functionalized magnetic beads with redox activity for sensitive electrochemical immunoassay of thyroid-stimulating hormone

A new electrochemical immunosensor for sensitive determination of thyroid-stimulating hormone (TSH) was designed by using redox-active nanogold-functionalized magnetic beads (GoldMag) as signal tags on the nanogold–graphene interface. To construct such GoldMag nanostructures, polyethyleneimine-functionalized magnetic beads (PEI-MBs) were initially prepared by using a wet chemical method, and the electroactive thionine molecules and gold nanoparticles were then alternately immobilized on the surface of PEI-MBs by using an opposite-charged adsorption technique and an in situ synthesis method, respectively. The synthesized GoldMag nanostructures were utilized as signal tags for the label of horseradish peroxidase-anti-TSH conjugates (HRP-anti-TSH). With a sandwich-type immunoassay format, the conjugated signal tags on the transducer were increased with the increasing TSH concentration in the sample, thus enhancing the signal of the electrochemical immunosensor due to the labeled HRP toward the catalytic reduction of H 2O 2. Under optimal conditions, the current was proportional to the logarithm of TSH concentration ranging from 0.01 to 20 μIU mL −1 in pH 6.0 HAc–NaAc containing 6 mM H 2O 2. The detection limit (LOD) was 0.005 μIU mL −1 TSH at 3 s B. The immunosensor displayed an acceptable reproducibility, stability and selectivity. In addition, the methodology was evaluated with human serum specimens, receiving good correlation with results from commercially available electrochemiluminescent analyzer.

One-step electrochemical immunoassay of biomarker based on nanogold-functionalized graphene sensing platform

A rapid and sensitive one-step electrochemical immunoassay for the determination of α-fetoprotein (AFP, as a model biomarker) was developed by immobilizing anti-AFP antibody on a nanogold-functionalized graphene interface. Initially, thionine molecules as electron mediators were conjugated onto the surface of graphene nanosheets, then gold nanoparticles were sandwiched onto the graphene, and then horseradish peroxidase-anti-AFP (HRP-anti-AFP) conjugates were immobilized on the nanogold surface. The presence of two-dimensional graphene nanosheets with high conductivity not only increased the surface coverage of the electrode, but also enhanced the immobilized amount of biomolecules. With the AFP analyte, the formed antigen–antibody complex was coated on the electrode surface, which partially hindered the immobilized HRP toward the catalytic reduction of H2O2 in the solution. Under optimal conditions, the electrochemical immunosensor displayed a wide dynamic range of 0.1–200 ng mL−1 with a detection limit (LOD) of 0.05 ng mL−1 AFP at 3sB. The reproducibility, selectivity and stability of the immunosensor were investigated with the acceptable results. In addition, the one-step immunoassay was evaluated and validated by assaying 5 positive and 5 negative serum specimens, and the obtained results were compared with those by the referenced electrochemiluminescent, receiving a good correlation between the two methods.

A facile method to prepare stable noncovalent functionalized graphene solution by using thionine

A novel noncovalent functionalization approach was presented here to exfoliate and stabilize the chemical converted graphene and the low-temperature exfoliated graphene in aqueous solution by using thionine. It was found that the thionine exhibited the π–π stacking force with the graphene sheets, and the attachment of thionine molecules onto the graphenes’ surfaces could obviously improve their solubility in water. The AFM observation further verified that the graphene sheets with single-layer to double-layer were existed in the dispersions. The electronic test indicated that the modified graphene sheets possessed excellent electronic properties.

Increased quantum efficiency in hybrid photoelectrochemical cell consisting of thionine and zinc oxide nanoparticles

Abstract In this paper we report our studies on hybrid photoelectrochemical cell made of thionine and zinc oxide nanoparticles. Nanostructured zinc oxide was synthesized in the laboratory by time and cost effective method. The photoelectrochemical cell yielded voltage of high magnitude (401.5 mV) and efficiency (1.21%) compared to other conventional photoelectrochemical cells. The morphology of the nanostructured zinc oxide was identified by X-ray diffraction and electron microscopy studies. Spectral studies indicated adsorption of the dye molecules on zinc oxide nanoparticles, the reason for efficient absorption of the incident photons. During photoexcitation the thionine molecules and the zinc oxide nanoparticles acted as donor–acceptor cluster which produced photovoltage.

Enhancement of Electrochemical Capacitance of Carbon Nanotubes by Polythionine Modification

AbstractThionine molecules have been electropolymerized onto different types of carbon nanotubes (CNT) using a cyclic voltammetry scanning technology, including multi‐walled carbon nanotubes, single‐walled carbon nanotubes and aligned carbon nanotubes. Results indicate that such prepared nanocomposites have combined the intrinsic faradic capacitance of polythionine with the double layer capacitance of polythionine‐CNT, and thus the polythionine modification obviously enhanced the CNT capacitance. Especially the carboxyl group modified multi‐walled carbon nanotubes, which have made their nanotube tips opened, allowed much more electropolymerization cycles and then obtained a most significant increment in capacitance than the other three ones.

A Novel Hydrogen Peroxide Amperometric Sensor based on Thionin Incorporated onto a Mo6S9‐xIx Nanowire Modified Glassy Carbon Electrode

AbstractA simple and enzymeless amperometric sensor for the detection of H2O2 based on a new kind of nanomaterial Mo6S9−xIx (MoSI) nanowires (NWs) was developed. The construction of the sensing platform was based on strong electrostatic interactions between negatively charged MoSI NWs and positively charged thionin molecules. MoSI NWs act as not only a good substrate for the immobilization of redox mediator thionin, but also a promoter for electrocatalysis of H2O2. The fabricated sensor showed a wide linear range over the concentration of H2O2 from 5 μM to 2.8 mM with a measurable lowest detection of 0.8 μM; furthermore, it exhibited good stability and reproducibility.

Biomolecule‐Doped Organic/Inorganic Hybrid Nanocomposite Film for Label‐Free Electrochemical Immunoassay of α‐1‐Fetoprotein

AbstractA new electrochemical immunosensor for the detection of α‐1‐fetoprotien (AFP) was developed based on AFP antibody (anti‐AFP)‐functionalized organic/inorganic hybrid nanocomposite membrane. To fabricate such a hybrid composite membrane, 3,4,9,10‐perylenetetracarboxylic acid‐bound thionine molecules (PTCTH) were initially doped into titania colloids (TiO2), and then gold nanoparticles and anti‐AFP were immobilized onto the composite film in turn. Comparison with the electrode fabricated only with thionine not 3,4,9,10‐perylenetetracarboxylic acid, the immunosensor with PTCTH exhibited high sensitivity and fast electron transfer. The presence of gold nanoparticles provided a good microenvironment for the immobilization of biomolecules, enhanced the surface coverage of protein, and improved the sensitivity of the immunosensor. The modified process was characterized by scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The surface topography of the membrane was investigated by scanning electron microscopy (SEM). Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 2.5 to 200.0 ng/mL towards AFP with a detection limit of 0.5 ng/mL (S/N=3). The stability, reproducibility and precision of the immunosensor were acceptable. Comparison with the conventional enzyme‐linked immunosorbent assay (ELISA), the present method did not require more labeled procedures and washing steps. Significantly, the detection methodology provides a promising approach for other proteins or biosecurities.

Electrochemical study of the thionine dye incorporated into ZSM-5 and HZSM-5 zeolites

The electrochemical properties of thionine dye adsorbed into ZSM-5 and HZSM-5 zeolites (TH/ZSM-5, TH/HZSM-5) are studied in 0.5 M KCl solution. The dye is strongly retained and not easily leached from the zeolites matrix. The samples are incorporated into the carbon paste electrode (TH/ZSM-5/P, TH/HZSM-5/P) for cyclic voltammetric measurements. The redox reactions of thionine incorporated into ZSM-5 zeolite contain a quasi-reversible, two-electron one proton in the pH range 1 to 10, but thionine-loaded HZSM-5 zeolite undergoes a quasi-reversible two-electron two-protons redox reaction under acidic conditions and a one proton two-electron redox reaction takes place under basic conditions. The separation of the anodic and cathodic potentials (E p) is high in thionine-loaded zeolites (>100) with respect to the solution of thionine (E p = 34 for ZSM-5/P and 36 mV for HZSM-5/P), indicating that there are strong interaction between thionine molecules and the zeolites. The midpoint potentials (E m) for TH/ZSM-5/P and TH/HZSM-5/P are −0.203 and −0.381 V, respectively. However, the midpoint potentials for the solution of thionine for the electrode system of ZSM-5/P and HZSM-5/P are −0.335 and −0.407 V, respectively. Thus, thionine dye molecules incorporated into the zeolites can be reduced more easily with respect to solution of thionine. In various electrolyte solutions, the midpoint potentials remains constant, but the midpoint potential of the thionine-zeolite electrodes depends on the solution pH. Influence of the pH of the solution on the midpoint potential of an immobilized dye reveals that thionine molecules are accessible to protons. This property is ascribed to the formation of mesopores in the structure of our zeolites suffering from a calcination step.

Molecular mechanics studies of thionin blue in zeolite mordenite

The localization and arrangement of thionin blue (C 12H 10N 3S +) dye molecules in the zeolite mordenite framework is studied by molecular mechanics (MM) simulations. The computational results for dye molecule localization are compared to those from single crystal X-ray diffraction. Two low energy thionin orientations are observed. In both, the thionin molecules are inclined within the large 12-membered ring channels and indicate electrostatic interaction with the framework and with the extra-framework Na + ions. Molecule orientation and the determined S⋯O (3.12 and 3.13 Å), N⋯O (3.22 and 3.33 Å) and C⋯O (3.45 and 3.41 Å) distances from the dye molecule to the channel wall are in reasonable agreement with the values found by single crystal X-ray diffraction (S⋯O = 3.084 Å, N⋯O = 3.087 Å and C⋯O = 3.235 Å). Clustering of thionin molecules in the 12-membered ring channels is not observed. The calculated potential energies for these two low energy configurations are essentially the same (∼−2236 kJ/mol) The global minimum was confirmed by multiple simulation runs, using different starting orientations of the thionin molecules in the mordenite framework. Quench simulations were also performed to understand the energetics of diffusion of thionin molecules in mordenite. The calculated activation energy of diffusion, ∼12–15 kJ, is comparable to values reported in literature for molecular diffusion in zeolites.

RETRACTED: Studies on interactions of thionine with gold nanoparticles

The interactions of thionine with gold nanoparticles have been studied by using UV-vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. With addition of small amounts of gold nanoparticles, the absorption peak intensity of monomers of thionine decreases significantly, whereas that of H-type dimers of thionine increases. With further addition of gold nanoparticles, both the absorption peak intensities of the monomers and dimers of thionine increase, and the increasing magnitude of the peak intensity of the dimers is larger than that of monomers. The addition of gold nanoparticles makes the equilibrium between the monomer and H-type dimer forms of thionine move toward the dimer forms. Due to the binding between thionine and gold nanoparticles, the fluorescence quenching of thionine by gold nanoparticles is enhanced with increasing amounts of gold nanoparticles, and the quenching is both static and dynamic. TEM images show that the addition of thionine results in the formation of gold clusters, and further support the spectral results. Infrared spectroscopic studies show that the nitrogen atoms of both the NH 2 moieties of thionine strongly bind to the gold nanoparticle surfaces through the electrostatic interaction of thionine with gold nanoparticles. For 3-6 nm particles, the number of adsorbed thionine molecules per gold particle is about 1.21 x 10 3 . Thionine molecules can not only bind to a particle to form a compact monolayer via both the NH 2 moieties of thionine, but also bind to two particles via their two NH 2 moieties, respectively.