Dual-mode transfer response based on electrochemical and fluorescence signals for the detection of amyloid-beta oligomers (AßO).

An aptamer sensor has been developed utilizing a dual-mode and stimuli-responsive strategy for quantitative detection of AßO (amyloid-beta oligomers) through simultaneous electrochemical and fluorescence detection. To achieve this, we employed UIO-66-NH2 as a carrier container to load MB (Methylene Blue), and Fe3O4 MNPs (iron oxide magnetic nanoparticles) with aptamer (ssDNA-Fe3O4 MNPs) fixed on their surface for biological gating. The ssDNA-Fe3O4 MNPs were immobilized onto the surface of UIO-66-NH2 through hydrogen bonding between the aptamer and the -NH2 group on the surface of UIO-66-NH2, thereby encapsulating MB and forming ssDNA-Fe3O4@MB@UIO-66-NH2. During the detection of AßO, the aptamer selectively reacted with AßO to form the AßO-ssDNA-Fe3O4 complex, leading to its detachment from the surface of UIO-66-NH2. This detachment facilitated the release of MB, enabling its electrochemical detection. Simultaneously, the AßO-ssDNA-Fe3O4 complex was efficiently collected and separated using a magnet after leaving the container's surface. Furthermore, the addition of NaOH facilitated the disconnection of biotin modifications at the 3' end of the aptamer from the avidin modifications on the Fe3O4 MNPs. Consequently, the aptamer detached from the surface of Fe3O4 MNPs, resulting in the restoration of fluorescence intensity of FAM (fluorescein-5'-carboxamidite) modified at its 5' end for fluorescence detection. The dual-mode sensor exhibited significantly enhanced differential pulse voltammetry signals and fluorescence intensity compared to those in the absence of AßO. The sensor demonstrated a wide detection range of 10 fM to 10 µM, with a detection limit of 3.4 fM. It displayed excellent performance in detecting actual samples and holds promising prospects for early diagnosis of Alzheimer's disease.

A review on the clean-up technologies for heavy metal ions contaminated soil samples.

The soil contamination with heavy metal ions is one of the grave intricacies faced worldwide over the last few decades by the virtue of rapid industrialization, human negligence and greed. Heavy metal ions are quite toxic even at low concentration a swell as non-biodegradable in nature. Their bioaccumulation in the human body leads to several chronic and persistent diseases such as lung cancer, nervous system break down, respiratory problems and renal damage etc. In addition to this, the increased concentration of these metal ions in soil, beyond the permissible limits, makes the soil unfit for further agricultural use. Hence it is our necessity, to monitor the concentration of these metal ions in the soil and water bodies and adopt some better technologies to eradicate them fully. From the literature survey, it was observed that three main types of techniques viz. physical, chemical, and biological were employed to harness the heavy metal ions from metal-polluted soil samples. The main goal of these techniques was the complete removal of the metal ions or the transformation of them into less hazardous and toxic forms. Further the selection of the remediation technology depends upon different factors such as process feasibility/mechanism of the process applied, nature and type of contaminants, type and content of the soil, etc. In this review article, we have studied in detail all the three technologies viz. physical, chemical and biological with their sub-parts, mechanism, pictures, advantages and disadvantages.

A Highly-Sensitive Picric Acid Chemical Sensor Based on ZnO Nanopeanuts.

Herein, we report a facile synthesis, characterization, and electrochemical sensing application of ZnO nanopeanuts synthesized by a simple aqueous solution process and characterized by various techniques in order to confirm the compositional, morphological, structural, crystalline phase, and optical properties of the synthesized material. The detailed characterizations revealed that the synthesized material possesses a peanut-shaped morphology, dense growth, and a wurtzite hexagonal phase along with good crystal and optical properties. Further, to ascertain the useful properties of the synthesized ZnO nanopeanut as an excellent electron mediator, electrochemical sensors were fabricated based on the form of a screen printed electrode (SPE). Electrochemical and current-voltage characteristics were studied for the determination of picric acid sensing characteristics. The electrochemical sensor fabricated based on the SPE technique exhibited a reproducible and reliable sensitivity of ~1.2 µA/mM (9.23 µA·mM-1·cm-2), a lower limit of detection at 7.8 µM, a regression coefficient (R²) of 0.94, and good linearity over the 0.0078 mM to 10.0 mM concentration range. In addition, the sensor response was also tested using simple I-V techniques, wherein a sensitivity of 493.64 µA·mM-1·cm-2, an experimental Limit of detection (LOD) of 0.125 mM, and a linear dynamic range (LDR) of 1.0 mM-5.0 mM were observed for the fabricated picric acid sensor.

Two-dimensional ytterbium oxide nanodisks based biosensor for selective detection of urea.

Herein, we demonstrate synthesis and application of two-dimensional (2D) rectangular ytterbium oxide (Yb2O3) nanodisks via a facile hydrothermal method. The structural, morphological, compositional, crystallinity, and phase properties of as-synthesized nanodisks were carried out using several analytical techniques that showed well defined 2D rectangular nanodisks/sheet like morphologies. The average thickness and edge length of the nanosheet structures were 20 ± 5nm and 600 ± 50nm, respectively. To develop urea biosensor, glassy carbon electrodes (GCE) were modified with Yb2O3 nanodisks, followed by urease immobilization and Nafion membrane covering (GCE/Yb2O3/Urease/Nafion). The fabricated biosensor showed sensitivity of 124.84µAmM-1cm-2, wide linear range of 0.05-19mM, detection limit down to ~ 2µM, and fast response time of ~ 3s. The developed biosensor was also used for the urea detection in water samples through spike-recovery experiments, which illustrates satisfactory recoveries. In addition, the obtained desirable selectivity towards specific interfering species, long-term stability, reproducibility, and repeatability further confirm the potency of as-fabricated urea biosensor.

Synthesis and Characterization of Mimosa Pudica Leaves Shaped α-Iron Oxide Nanostructures for Ethanol Chemical Sensor Applications.

Herein, the synthesis of mimosa pudica leaves shaped a-iron oxide (α-Fe2O3) nanostructures is reported through simple and facile hydrothermal process. The prepared α-Fe2O3 nanostructures were characterized in terms of their morphological, structural, compositional and optical properties through a variety of characterization techniques such as FESEM, EDS, XRD, FTIR and Raman spectroscopy. The detailed characterizations revealed the well-crystallinity and dense growth of mimosa pudica leaf shaped α-Fe2O3 nanostructures. Further, the prepared nanomaterials were used as efficient electron mediator to fabricate sensitive ethanol chemical sensor. The fabricated sensor exhibited a high sensitivity of -30.37 µAmM(-1) cm(-2) and low detection limit of -0.62 µM. The observed linear dynamic range (LDR) was in the range from 10 µM-0.625 µM.

Low-temperature synthesis of α-Fe2O3 hexagonal nanoparticles for environmental remediation and smart sensor applications.

This work demonstrates the successful synthesis and characterizations of α-Fe2O3 hexagonal nanoparticles and their effective utilization for the degradation of hazardous Rhodamine B (RhB) dye and smart chemical sensor applications. The as-synthesized materials were characterized by various analytical techniques which revealed that the prepared nanoparticles are well-crystalline, possessing hexagonal shape, grown in high-density and well matched with the rhombohedral α-Fe2O3 structures. The as-synthesized α-Fe2O3 nanoparticles were used as efficient photocatalyst for the photocatalytic degradation of RhB-dye under light illumination which showed substantial degradation (~79%) of RhB-dye in 140 min. The considerable photo-degradation of RhB-dye attributed to the unique morphology of the synthesized α-Fe2O3 nanoparticles which might import the effective electron/hole separation and generate the large number of oxy-radicals. Moreover, the synthesized α-Fe2O3 nanoparticles were utilized as efficient electron mediators for the fabrication of 4-nitrophenol chemical sensor in aqueous media. The fabricated chemical sensor exhibited a high-sensitivity of ~367.6 µA (mol L(-1))(-1) cm(-2) and an experimental detection limit of ~1.56×10(-3) mol L(-1) in a short response time of ~10.0 s with linearity in the range of 1.56×10(-3)-12.5×10(-3) mol L(-1) and correlation coefficient (R) of ~0.99963. These investigations demonstrated that the simply synthesized α-Fe2O3 nanoparticles can effectively be used as efficient photocatalyst for the photocatalytic degradation of organic dyes and effective electron mediators for the fabrication of highly sensitive chemical sensors in aqueous medium.

Visible-light-driven photocatalytic and chemical sensing properties of SnS2 nanoflakes.

This work demonstrated the successful and facile large-scale synthesis and characterizations of SnS2 nanoflakes. The detailed morphological studies revealed that the synthesized products were nanoflakes and were grown in large quantity. The XRD pattern and detailed compositional studies confirmed that the synthesized SnS2 nanoflakes were well-crystalline and possessing hexagonal SnS2 phase. The synthesized SnS2 nanoflakes were used as efficient photocatalysts for photocatalytic degradation and effective electron mediators for the fabrication of chemical sensor. The photocatalytic properties of SnS2 nanoflakes towards the photocatalytic degradation of Rhodamine B dye under visible light irradiation showed reasonably good degradation of ~61%. Moreover, the as-synthesized SnS2 nanoflakes were used as efficient electron mediators for the fabrication of nitroaniline chemical sensor by simple I-V technique. Very high-sensitivity of ~ 505.82±0.02 mAcm(-2).(mole/L)(-1) and experimental detection limit of ~15×10(-6) (mole/L) in a short response time of ~10.0 s with LDR in the range of 15.6×10(-6)-0.5×10(-3) mole L(-1) were observed for the fabricated nitroaniline chemical sensor. The observed results indicated that the SnS2 nanoflakes can efficiently be used as visible-light-driven photocatalysts and the fabrication of ultra-high sensitive chemical sensors.

Growth and properties of Ag-doped ZnO nanoflowers for highly sensitive phenyl hydrazine chemical sensor application.

We report here the fabrication of a robust, highly sensitive, reliable and reproducible phenyl hydrazine chemical sensor using Ag-doped ZnO nanoflowers as efficient electron mediators. The Ag-doped ZnO nanoflowers were synthesized by facile hydrothermal process at low-temperature and characterized in detail in terms of their morphological, structural, compositional and optical properties. The detailed morphological and structural characterizations revealed that the synthesized nanostructures were flower-shaped, grown in very high-density, and possessed well-crystalline structure. The chemical composition confirmed the presence of Ag into the lattices of Ag-doped ZnO nanoflowers. High sensitivity of ≈ 557.108 ± 0.012 mAcm(-2)(mol L(-1))(-1) and detection limit of ≈ 5 × 10(-9) mol L(-1) with correlation coefficient (R) of 0.97712 and short response time (10.0 s) were observed for the fabricated chemical sensor towards the detection of phenyl hydrazine by using a simple current-voltage (I-V) technique. Due to high sensitivity and low-detection limit, it can be concluded that Ag-doped ZnO nanoflowers could be an effective candidate for the fabrication of phenyl hydrazine chemical sensors.

Ultra-high sensitive ammonia chemical sensor based on ZnO nanopencils.

This paper reports a very simple, reliable and facile methodology to fabricate ultra-high sensitive liquid ammonia chemical sensor using well-crystalline hexagonal-shaped ZnO nanopencils as an efficient electron mediator. A low-temperature facile hydrothermal technique was used to synthesize ZnO nanopencils. The synthesized nanopencils were characterized in detail in terms of their morphological, structural and optical properties which confirmed that the synthesized nanomaterial is well-crystalline, possessing wurtzite hexagonal phase and possess very good optical properties. A very high sensitivity of ≈ 26.58µAcm(-2)mM(-1) and detection limit of ≈ 5nM with a correlation coefficient (R) of 0.9965 and a response time of less than 10s were observed for the fabricated liquid ammonia by I-V technique. To the best of our knowledge, by comparing the literature, it is confirmed that the fabricated sensor based on ZnO nanopencils exhibits highest sensitivity and lowest detection limit for liquid ammonia. This research opens a way that simply synthesized nanomaterials could be used as efficient electron mediators for the fabrication of efficient liquid ammonia chemical sensors.

Synthesis and characterizations of Cd-doped ZnO multipods for environmental remediation application.

Well-crystalline Cd-doped ZnO multipods were synthesized by simple and facile hydrothermal process by using zinc chloride, cadmium chloride, hexamethylenetetramine and ammonium hydroxide at low-temperature. The synthesized materials were characterized in terms of their morphological, structural, compositional and optical properties. The morphological investigations done by field emission scanning electron microscopy (FESEM) reveal that the synthesized products are multipods shaped and grown in high density. The structural and compositional properties, observed by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) attached with FESEM and Fourier transform infrared (FTIR) spectroscopy exhibit that the synthesized multipods are well-crystalline and possessing wurtzite hexagonal phase pure Cd-doped ZnO. The as-synthesized Cd-doped ZnO multipods exhibited good optical properties as was confirmed by UV-vis. spectroscopy. Finally, the as-synthesized Cd-doped ZnO multipods were used environmental remediation application. For this, the synthesized multipods were used as an effective photocatalyst for the photocatalytic degradation of acridine orange (AO) which exhibit -92.4% degradation within 90 min. This work demonstrates that doped ZnO materials could be used as efficient photocatalyst for the photocatalytic degradation of various organic dyes and chemicals.

High-yield synthesis of well-crystalline alpha-Fe2O3 nanoparticles: structural, optical and photocatalytic properties.

In this paper, the high-yield facile synthesis, detailed characterization and photocatalytic application of alpha-Fe2O3 nanoparticles are reported. The synthesis was done via simple hydrothermal process by using aqueous mixtures of iron chloride, hexamethylenediamine and NH3 x H2O at 110 degrees C. The morphologies of the synthesized products were examined by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) which confirmed that the synthesized structures are almost spherical shaped nanoparticles with the average diameters of -35 +/- 5 nm, and are grown in high yield. The detailed structural characterizations and composition of the as-synthesized nanoparticles were investigated by using X-ray diffraction (XRD), high-resolution TEM (HRTEM), energy dispersive spectroscopy (EDS) attached with FESEM and Fourier transform infrared spectroscopy (FTIR) which substantiated that the as-synthesized nanoparticles are well crystalline and pure alpha-Fe2O3. The UV-Vis absorption spectrum of the synthesized nanoparticles demonstrated the existence of two optical band gaps which correspond to direct and indirect transitions, respectively. The as-synthesized alpha-Fe2O3 nanoparticles exhibit good photocatalytic properties on photocatalytic degradation of methylene blue.