In recent decades, H2O2 has been promoted as a health indicator because its moderate to high levels can cause some health problems. Herein, we developed a new fluorescent nanoprobe for rapid, selective and sensitive detection of H2O2. The fluorescent nanoprobe is composed of fluorescein dye (FLS) as a fluorescent probe and MnO2 nanosheets (MnO2 NS) as a quencher. In this study, H2O2 can reduce MnO2 NS in the synthesized composite and release FLS, causing sufficient recovery of fluorescent signal related to the concentration of H2O2. The nanoprobe, with λex/λem at 495/515 nm, has a linear range of 0.04–30 μM, with a limit of detection (LOD) of 7.5 nM and a limit of quantitation (LOQ) of 21 nM. The mean relative standard deviation (RSD) was 2.6% and the applicability of the method was demonstrated by the determination of H2O2 in water and cosmetic samples.

In recent decades, H2O2 has been promoted as a health indicator because its moderate to high levels can cause some health problems. Herein, we developed a new fluorescent nanoprobe for rapid, selective and sensitive detection of H2O2. The fluorescent nanoprobe is composed of fluorescein dye (FLS) as a fluorescent probe and MnO2 nanosheets (MnO2 NS) as a quencher. In this study, H2O2 can reduce MnO2 NS in the synthesized composite and release FLS, causing sufficient recovery of fluorescent signal related to the concentration of H2O2. The nanoprobe, with λex/λem at 495/515 nm, has a linear range of 0.04–30 μM, with a limit of detection (LOD) of 7.5 nM and a limit of quantitation (LOQ) of 21 nM. The mean relative standard deviation (RSD) was 2.6% and the applicability of the method was demonstrated by the determination of H2O2 in water and cosmetic samples.

An innovative label free electrochemical aptasensor was developed for the analysis of oxaliplatin (OXAL) for the first time. The DNA oligonucleotide (aptamer) was successfully fabricated, by covalently attaching the amino terminus of the functional DNA on the glassy carbon electrode (GCE) surface modified with reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) loaded with AuPd nanoparticles (AuPd NPs@rGO/MWCNTs/GCE). The stepwise assembly process of aptasensor on AuPd NPs@rGO/MWCNTs/GCE was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The aptamer-OXAL complex formation led to inhibition the electron transfer of Fe(CN)63−/4- on the electrode interface, which was clearly observed by decreasing the peak current of the redox probe. Furthermore, we managed to quantitatively measure OXAL by adding different concentrations of OXAL, while monitoring the decrease of differential pulse voltammogram (DPV) responses of the redox probe. Under the optimized conditions, the electrochemical aptasensor exhibited a linear range of 0.1–170.0 nmol L−1 with LOD of 60.0 pmol L−1. Next, we successfully applied the aptasensor calibrated system to determine OXAL in pharmaceutical injection and human biological samples.

In this study, an electrochemical aptamer based sensor (aptasensor) was proposed for specific recognition of histamine (HIS). The electrochemical aptasensor based on fabrication of glassy carbon electrode (GCE) with molecular imprinted polymer (MIP) and DNA aptamers on gold nanoparticles (AuNPs) and carboxylated carbon nanotubes (cCNTs) (MIP-apta/AuNPs/cCNTs/GCE). The aptasensor exhibits high selectivity towards HIS detection as it has two recognition elements which are MIP cavities and aptamer interaction. Upon exposure of MIP-apt/AuNPs/cCNTs/GCE to HIS, the current of redox probe was decreased that depends on the template (HIS) concentration. The effects of aptamer concentration, incubation time, pH and AuNPs electro-deposition time were optimized. Differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques were used to analyze HIS in complicated matrices. Favorable performance of MIP-apt/AuNPs/cCNTs/GCE was achieved with linearity ranges of 0.46–35 nmol L−1 and 0.35–35 nmol L−1 with limits of detection (LODs, S/N = 3) of 0.15 nmol L−1 and 0.11 nmol L−1 using DPV and EIS, respectively. The fabricated aptasensor displayed high selectivity, desirable reproducibility and stability. The MIP-apt/AuNPs/cCNTs/GCE was used to detect HIS in human plasma and canned tuna samples with good recoveries % and RSDs %.

In this study, an electrochemical aptamer based sensor (aptasensor) was proposed for specific recognition of histamine (HIS). The electrochemical aptasensor based on fabrication of glassy carbon electrode (GCE) with molecular imprinted polymer (MIP) and DNA aptamers on gold nanoparticles (AuNPs) and carboxylated carbon nanotubes (cCNTs) (MIP-apta/AuNPs/cCNTs/GCE). The aptasensor exhibits high selectivity towards HIS detection as it has two recognition elements which are MIP cavities and aptamer interaction. Upon exposure of MIP-apt/AuNPs/cCNTs/GCE to HIS, the current of redox probe was decreased that depends on the template (HIS) concentration. The effects of aptamer concentration, incubation time, pH and AuNPs electro-deposition time were optimized. Differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques were used to analyze HIS in complicated matrices. Favorable performance of MIP-apt/AuNPs/cCNTs/GCE was achieved with linearity ranges of 0.46–35 nmol L−1 and 0.35–35 nmol L−1 with limits of detection (LODs, S/N = 3) of 0.15 nmol L−1 and 0.11 nmol L−1 using DPV and EIS, respectively. The fabricated aptasensor displayed high selectivity, desirable reproducibility and stability. The MIP-apt/AuNPs/cCNTs/GCE was used to detect HIS in human plasma and canned tuna samples with good recoveries % and RSDs %.

The study of biologically important Cu2+ and S2− ions has drawn great attention in the recent years since an abnormal level of these ions is an indication for health impairment. Therefore, a reliable strategy for effective fluorescence determination of Cu2+ and S2− ions was developed. Simply, the method based on economical plant-dependent thermolysis procedure for efficient green synthesis of water dispersible luminescent polyamine-based carbon dots (PA@C-dots) utilizes Vitis vinifera juice as precursor with a high quantum yield (32.1%) and good photo-stability. The fluorescent PA@C-dots were characterized by different spectroscopical, physical, and structural techniques. Furthermore, the synthesized PA@C-dots can be used as an efficient dual functional fluorescent probe for the sensitive and selective estimation of Cu2+ and S2− ions. The incorporation of Cu2+ ions and their adsorption on the surface of PA@C-dot skeleton leads to the respectable fluorescence quenching of C-dots (turn-off mode). The Cu2+-PA@C-dot was found to be sensitive to S2− ions. The addition of S2− recovers the fluorescence (turn-on mode) of Cu2+-PA@C-dots, thanks to its capacity for withdrawing Cu2+ from the shell of PA@C-dots. Fluorescence quenching in the range of 0.07–60 μM Cu2+ was obtained with LOD and LOQ of 0.02 and 0.066 μM, respectively. Sulfide detection provides linearity in the range of 0.8 to 95 μM with LOD and LOQ of 0.24 and 0.79 μM, respectively. The optimal excitation and emission wavelengths for all experiments are 435 nm and 498 nm, respectively. Experiment results elucidate that the proposed method is suitable for Cu2+and S2− ion detection in environmental water samples.

The study of biologically important Cu2+ and S2− ions has drawn great attention in the recent years since an abnormal level of these ions is an indication for health impairment. Therefore, a reliable strategy for effective fluorescence determination of Cu2+ and S2− ions was developed. Simply, the method based on economical plant-dependent thermolysis procedure for efficient green synthesis of water dispersible luminescent polyamine-based carbon dots (PA@C-dots) utilizes Vitis vinifera juice as precursor with a high quantum yield (32.1%) and good photo-stability. The fluorescent PA@C-dots were characterized by different spectroscopical, physical, and structural techniques. Furthermore, the synthesized PA@C-dots can be used as an efficient dual functional fluorescent probe for the sensitive and selective estimation of Cu2+ and S2− ions. The incorporation of Cu2+ ions and their adsorption on the surface of PA@C-dot skeleton leads to the respectable fluorescence quenching of C-dots (turn-off mode). The Cu2+-PA@C-dot was found to be sensitive to S2− ions. The addition of S2− recovers the fluorescence (turn-on mode) of Cu2+-PA@C-dots, thanks to its capacity for withdrawing Cu2+ from the shell of PA@C-dots. Fluorescence quenching in the range of 0.07–60 μM Cu2+ was obtained with LOD and LOQ of 0.02 and 0.066 μM, respectively. Sulfide detection provides linearity in the range of 0.8 to 95 μM with LOD and LOQ of 0.24 and 0.79 μM, respectively. The optimal excitation and emission wavelengths for all experiments are 435 nm and 498 nm, respectively. Experiment results elucidate that the proposed method is suitable for Cu2+and S2− ion detection in environmental water samples.

An innovative electrochemical nanoprobe, for analysis of salinomycin (SAL), was proposed. The nanoprobe based on decoration of glassy carbon electrode (GCE) with 3D rose like La3+@ ZrO2 supported on reduced graphene oxide (RGO) nanosheets. The 3D rose like La3+@ ZrO2 was synthesized via sintering process. The successful decoration of 3D rose like La3+@ ZrO2 on the surface of RGO was characterized using different spectroscopic and analytical techniques. The obtained voltammetric results confirmed the good electrochemical performance of 3D rose like La3+@ ZrO2 in terms of lower peak potential (Epc) and higher cathodic current (Ipc). Moreover, the modified nanoprobe showed wide linearity range (0.34–115 × 10−8 M), lower detection limit (0.11 × 10−8 M) and higher selectivity. Besides, the nanocomposite showed good applicability for analysis of SAL in biological fluids and during pharmacokinetic evaluation in rabbit plasma. The obtained results opens a new venue for the determination of futuristic drug, SAL, during pharmacokinetic and pharmacodynamics studies.

An innovative electrochemical nanoprobe, for analysis of salinomycin (SAL), was proposed. The nanoprobe based on decoration of glassy carbon electrode (GCE) with 3D rose like La3+@ ZrO2 supported on reduced graphene oxide (RGO) nanosheets. The 3D rose like La3+@ ZrO2 was synthesized via sintering process. The successful decoration of 3D rose like La3+@ ZrO2 on the surface of RGO was characterized using different spectroscopic and analytical techniques. The obtained voltammetric results confirmed the good electrochemical performance of 3D rose like La3+@ ZrO2 in terms of lower peak potential (Epc) and higher cathodic current (Ipc). Moreover, the modified nanoprobe showed wide linearity range (0.34–115 × 10−8 M), lower detection limit (0.11 × 10−8 M) and higher selectivity. Besides, the nanocomposite showed good applicability for analysis of SAL in biological fluids and during pharmacokinetic evaluation in rabbit plasma. The obtained results opens a new venue for the determination of futuristic drug, SAL, during pharmacokinetic and pharmacodynamics studies.

Herein, a novel “ON-OFF” colorimetric and fluorometric chemosensor; 1N-allyl-2-(2, 5-dimethoxyphenyl)-4, 5-diphenyl-1H-imidazole (ADPPI), was constructed for sequential determination of Cu2+ and S2− ions in aqueous media. The interaction between chemosensor ADPPI and different metal cations was investigated using UV-VIS and fluorimetric spectroscopy. ADPPI showed a favorable and good interaction with Cu2+ ions producing blue colored solution peaked at 610 nm with blue fluorescence at λem. = 447 nm. The produced complex between Cu2+ ions and ADPPI can be used as a cascade probe for detection of S2− ions. The detection limits (LODs) were 1.01 nM and 1.25 μM for Cu2+ and S2− ions, respectively (the lowest between the family of colorimetric and fluorometric chemosensors). To further increase the applicability of the proposed method, Cu2+ and S2− ions concentrations were measured in environmental water samples.