Preparation of a Red-Emitting, Chitosan-Stabilized Copper Nanocluster Composite and Its Application as a Hydrogen Peroxide Detection Probe in the Analysis of Water Samples

Hydrogen peroxide (H₂O₂) is an important reactive oxygen species that mediates a variety of physiological functions in biological processes, and it is an essential mediator in food, pharmaceutical, and environmental analysis. However, H₂O₂ can be dangerous and toxic at certain concentrations. It is crucial to detect the concentration of H₂O₂ in the environment for human health and environmental protection. Herein, we prepared the red-emitting copper nanoclusters (Cu NCs) by a one-step method, with lipoic acid (LA) and sodium borohydride as protective ligands and reducing agents, respectively, moreover, adding chitosan (CS) to wrap LA-Cu NCs. The as-prepared LA-Cu NCs@CS have stronger fluorescence than LA-Cu NCs. We found that the presence of H₂O₂ causes the fluorescence of LA-Cu NCs@CS to be strongly quenched. Based on this, a fluorescent probe based on LA-Cu NCs@CS was constructed for the detection of H₂O₂ with a limit of detection of 47 nM. The results from this research not only illustrate that the as--developed fluorescent probe exhibits good selectivity and high sensitivity to H₂O₂ in environmental water samples but also propose a novel strategy to prepare red-emitting copper nanoclusters (Cu NCs) by a one-step method.

Detection of hydrogen peroxide and glucose with a novel fluorescent probe by the enzymatic reaction of amino functionalized MOF nanosheets

Amino-functionalized two-dimensional (2D) MOFs have great potential in biosensors due to their excellent water solubility, high fluorescence, large specific surface area, good adsorption properties and good ability to enrich the target analytes. Fluorescence detection of hydrogen peroxide and glucose mostly relies on monitoring the single fluorescence intensity changes in a single excitation wavelength. Here, a ratiometric fluorescence sensor based on NH₂-MIL-53(Al) nanosheets to sensitively detect H₂O₂ and glucose through enzymatic reactions was developed. o-Phenylenediamine (OPD) was oxidized by H₂O₂ in the presence of horseradish peroxidase (HRP). Then, the oxidation product could be self-assembled on NH₂-MIL-53(Al) nanosheets by hydrogen bonding and π-π stacking. The orbital interaction or the fluorescence resonance energy transfer (FRET) between the nanosheets and the oxidation product could effectively quench the fluorescence of the nanosheets at 433 nm. At the same time, the oxidation product provided a new emission peak at 564 nm. The fluorescence ratio signal changes generated by this oxidation process were used to stably and sensitively detect H₂O₂ and glucose. Structural and mechanistic analysis was carried out by calculation methods such as AICD and ORCA to explore the π electron structure characteristics, the hole/electron orbitals and the quenching phenomenon. The detection limit was 26.9 nM for H₂O₂ and 0.041 μM for glucose. The detection of glucose in human serum has a satisfactory recovery of 97.4-102.8%. It is clear that the sensor has a good application prospect in real sample analysis.

Sensitive determination of hydrogen peroxide in real water samples by high spin peroxo complex

In this paper, a fast, cheap, simple, sensitive and selective spectrophotometric method based on high spin peroxo-Fe(III)-EDTA complex in the alkaline medium was developed for the determination of hydrogen peroxide (H₂O₂) in real water samples. The purple-coloured complex with a maximum absorbance at a wavelength of 525 nm was formed. Various parameters such as type of stabilizer reagent and its concentration, reaction time, Fe(III), EDTA and NH₃ concentration were optimized. The method was confirmed with the Beer’s law with a molar absorption coefficient of 267.36 L mol^-1 cm^-1 in the 8.3 ×10^-6 –4.08 ×10^-3 mol/L concentration range. Sandell’s sensitivity of the proposed method was also calculated as 0.188 μg/cm² . LOD and LOQ were determined as 2.5 ×10^-6 and 8.3 ×10^-6 mol/L, respectively. Intraday and interday relative standard deviation of the proposed method for 2.0 ×10^-4 mol / L of H₂O₂ were found as 1.5% and 6.1%, respectively. The developed method is suitable for fast monitoring of H₂O₂ in different types of aqueous water samples without any sample preparation steps and acceptable recovery values between 90% and 118% were obtained. In the sample analysis, H₂O₂ removed solutions from the real water samples were used for blank correction in their analysis and this process provides more reliable and accurate results in real sample analysis.

Biocatalyst and Colorimetric/Fluorescent Dual Biosensors of H2O2 Constructed via Hemoglobin-Cu3(PO4)2 Organic/Inorganic Hybrid Nanoflowers

In this article, the three-dimensional hemoglobin (Hb)-Cu₃(PO₄)₂ organic/inorganic hybrid nanoflowers (Hb-Cu₃(PO₄)₂ HNFs) self-assembled by nanopetals were synthesized via a facile one-pot green synthetic method. The compositions and microstructure of the Hb-Cu₃(PO₄)₂ HNFs were well-characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-vis spectrometry, respectively. The as-prepared Hb-Cu₃(PO₄)₂ HNFs were to be used as a biocatalyst to construct colorimetric/fluorescent dual biosensors. The experimental results show that the colorimetric/fluorescent dual biosensors exhibited two linear responses in the range of 2-10 ppb and 20-100 ppb for H₂O₂. The colorimetric and fluorescent detection limits were 0.1 and 0.01 ppb, respectively. Compared with the free Hb, the biocatalytic activity of the Hb-Cu₃(PO₄)₂ HNFs can be improved for 3-4 times under optimal conditions. The sensing performance of these Hb-Cu₃(PO₄)₂ HNF-based dual biosensors can be contributed such that the active sites of Hb molecules were more exposed on the surface of the Cu₃(PO₄)₂ nanopetals. Second, the unique nanopetal-assembled hybrid flowerlike structure was favorable to contact the detected substance with the biosensors. The dual biosensors were successfully applied for the determination of H₂O₂ in rainwater, tap water, and waste water samples. These results show that the dual biosensors had a potential application in the field of medical analysis, environmental monitoring, and food engineering.

Hemin-Modified SnO2/Metglas Electrodes for the Simultaneous Electrochemical and Magnetoelastic Sensing of H2O2

In this work, we present a simple and efficient method for the preparation of hemin-modified SnO2 films on Metglas ribbon substrates for the development of a sensitive magneto-electrochemical sensor for the determination of H2O2. The SnO2 films were prepared at low temperatures, using a simple hydrothermal method, compatible with the Metglas surface. The SnO2 film layer was fully characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), photoluminescence (PL) and Fourier Transform-Infrared spectroscopy (FT-IR). The properties of the films enable a high hemin loading to be achieved in a stable and functional way. The Hemin/SnO2-Metglas system was simultaneously used as a working electrode (WE) for cyclic voltammetry (CV) measurements and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The CV scans reveal direct reduction and oxidation of the immobilized hemin, as well as good electrocatalytic response for the reduction of H2O2. In addition, the magnetoelastic resonance (MR) technique allows the detection of any mass change during the electroreduction of H2O2 by the immobilized hemin on the Metglas surface. The experimental results revealed a mass increase on the sensor during the redox reaction, which was calculated to be 767 ng/μM. This behavior was not detected during the control experiment, where only the NaH2PO4 solution was present. The following results also showed a sensitive electrochemical sensor response linearly proportional to the concentration of H2O2 in the range 1 × 10−6–72 × 10−6 M, with a correlation coefficient of 0.987 and detection limit of 1.6 × 10−7 M. Moreover, the Hemin/SnO2-Metglas displayed a rapid response (30 s) to H2O2 and exhibits good stability, reproducibility and selectivity.

Chromogenic, Fluorescent, and Redox Sensors for Multichannel Imaging and Detection of Hydrogen Peroxide in Living Cell Systems

Hydrogen peroxide (H₂O₂) is an important reactive oxygen species (ROS). Maintaining the H₂O₂ concentration at a normal level is critical to achieve the normal physiological activities of cells, which otherwise might trigger various diseases. Therefore, it is necessary to develop new and practical multisignaling sensors for both visualization of intracellular H₂O₂ and accurate detection of extracellular H₂O₂. In this paper, a novel multichannel signaling fluorescence-electrochemistry combined probe 1 (FE-H₂O₂) is presented for imaging and detection of H₂O₂ in living cell systems. In our design, the probe FE-H₂O₂ consists of a H₂O₂ reaction site and 4-ferrocenyl(vinyl)pyridine unit which affords chromogenic, fluorescent, and electrochemical signals. These structural motifs yield a combined chromogenic, fluorescent, and redox sensor in a single molecule. Probe FE-H₂O₂ showed a "Turn-On" fluorescence response to H₂O₂, which can be used for monitoring intracellular H₂O₂ in vivo. Furthermore, the electrochemical response of probe FE-H₂O₂ was decreased after the addition of H₂O₂, which can be applied for accurate detection of H₂O₂ released from living cells. When the fluorescence imaging method is combined with electrochemical analysis technology, it is hopeful that the well-designed multimodule probe can serve as a practical tool for understanding the metabolism and homeostasis of H₂O₂ in a complex biological system.

Photodynamic therapy evaluation of methoxypolyethyleneglycol-thiol-SPIONs-gold-meso-tetrakis(4-hydroxyphenyl)porphyrin conjugate against breast cancer cells

Magnetic field enhanced photodynamic therapy is an effective non-invasive technique for the eradication of cancer diseases. In this report, magnetic field enhancement of the photodynamic therapy (PDT) efficacy of a novel methoxypolyethyleneglycol-thiol-SPIONs-gold-meso-tetrakis(4-hydroxyphenyl)porphyrin conjugate (nano-drug) against MCF-7 breast cancer cells was evaluated. The nano-drug exhibited excellent blue and red emissions under suitable ultraviolet (380 nm) and visible (430 nm) excitations and was well taken up by the cells without any significant dark cytotoxicity after 24 h post-incubation. However, after exposure of cells to light for about 15 min, high rate of cell death was observed in a dose-dependent manner. In addition, the cells that were exposed to external magnetic field displayed higher phototoxicity than the non-exposed cells. Altogether, these results suggest that the nano-porphyrin drug system can function as a new promising magnetic-field targeting agent for theranostic photodynamic eradication of cancer diseases.

A novel fluorimetric sensing strategy for highly sensitive detection of phytic acid and hydrogen peroxide

In this paper, we developed a sensitive sensor for phytic acid (PA) and hydrogen peroxide (H₂O₂) detection based on glutathione-functionalized graphene quantum dots (GQDs@GSH). The fluorescence of GQDs@GSH was found to be effectively quenched by Fe³⁺ ions via photo-induced electron transfer (PET) process. Upon the addition of PA to GQDs@GSH/Fe³⁺ system, the fluorescence of GQDs@GSH was significantly restored due to the strong chelating and reducing ability of PA, Fe³⁺ ions could be reduced to Fe²⁺ ions by PA and formed PA/Fe²⁺ complex. Therefore, the "off-on" fluorescence method was constructed to detect PA by using GQDs@GSH/Fe³⁺ as a fluorescent probe. Furthermore, the method can be used for the detection of H₂O₂. H₂O₂ can destroy the chelate structure of PA/Fe²⁺, release Fe²⁺ ions and oxidize Fe²⁺ ions to produce Fe³⁺ ions, leading to the fluorescence quenching of GQDs@GSH again. Under optimal conditions, the fluorescence sensing platform showed good linear relationship between the relative fluorescence intensity I/I₀ and the concentration of PA and H₂O₂ in the range of 0.05-3 μmol L^-1 and 0.5-10 μmol L^-1, respectively. The detection limits of PA and H₂O₂ were 14 nmol L^-1 and 0.134 μmol L^-1, respectively. Furthermore, the fluorescence assay method was also applied in real sample analysis and satisfactory results were obtained.

Enhanced peroxidase-like activity of porphyrin functionalized ZnFe2O4 hollow nanospheres for rapid detection of H2O2 and glucose

Using a simple one-pot solvothermal method, binary metal oxide, magnetic and hollow ZnFe₂O₄ nanospheres functionalized with 5,10,15,20-tetrakis(4-carboxylpheyl)-porphyrin (Por–ZnFe₂O₄ HSs) were prepared and subsequently applied as a substitute for natural peroxidase.

Cobalt and nickel bimetallic sulfide nanoparticles immobilized on montmorillonite demonstrating peroxidase-like activity for H2O2 detection

In this study, ternary transition metal sulfide (cobalt and nickel sulfides) nanoparticles were anchored on the surface of montmorillonite (MMT) by a facile one-pot hydrothermal method.

Design, synthesis and properties of a reactive chromophoric/fluorometric probe for hydrogen peroxide detection

A succinct chromophoric/fluorometric probe, AVPM, for sensitive and selective H₂O₂detection.

Silica-coated triangular gold nanoprisms as distance-dependent plasmon-enhanced fluorescence-based probes for biochemical applications

Plasmon-enhanced fluorescence (PEF)-based anisotropic nanostructures are considered extremely promising tools for improving the inherent problems of traditional fluorophores and for detecting important biomolecules with high sensitivity. Herein, a novel triangular gold nanoprism (AuNPR)-based fluorescence probe, AuNPR@SiO₂@12,17-tetramethyl-3-dihydro-(2s-trans)-thyl-7(Ce6), was developed for PEF by virtue of multiple "hot spots" of AuNPRs. Fluorescence enhancement of fluorophores can be realized owing to the larger and stronger electromagnetic fields located at the sharp tips of AuNPRs than those on spherical particles and nanorods. A silica shell was employed as a rigid spacer to precisely adjust the distance between the AuNPR and Ce6 for optimal PEF. Owing to the improved fluorescence signal, core-shell PEF-based AuNPRs can be applied as a turn-on probe for highly selective and sensitive detection of pyrophosphate (PPi) with a desirable detection limit of 0.2 μM using a displacement approach. Meanwhile, we demonstrated that these nanomaterials have great potential for real-time monitoring of polymerase chain reaction (PCR) products, successfully revealing an approximately 240 times higher detectable fluorescence response than that of traditional gel electrophoresis. Furthermore, cell imaging indicates the potential applications of PEF-based probes in living cells.

A dialdehyde–diboronate-functionalized AIE luminogen: design, synthesis and application in the detection of hydrogen peroxide

A dialdehyde–diboronate-functionalized tetraphenylethene (TPE-DABF) was reported as a H₂O₂-specific AIE luminogen.

Exploiting novel process windows for the synthesis of meso-substituted porphyrins under continuous flow conditions

Porphyrin synthesis by classical methods frequently involves harsh conditions yielding products with poor scalability. Herein, a continuous flow approach is described, thus demonstrating a scaled-up procedure in a safe and highly pure manner.

A new fluorescence and colorimetric sensor for highly selective and sensitive detection of glucose in 100% water

A new naphthalimide derivative containing hexanoic acid and boronate groups was designed and synthesized.