Mohammed M. Rahman

Multi-layered mesoporous TiO2 thin films with large pores and highly crystalline frameworks for efficient photoelectrochemical conversion

Mesoporous thin films with various compositions are unique architectures for photoelectrochemical (PEC) solar cells. In this paper, we report the synthesis of highly ordered, multi-layered, continuous mesoporous TiO2 thin films with uniform large pores, crystalline walls and tunable film thickness, via a ligand-assisted evaporation induced self assembly (EISA) method. A Ti(acetylacetone) precursor and a diblock copolymer PEO-b-PS are employed for the controlled assembly of the TiO2/template mesostructure, followed by a two-step pyrolysis that generates carbon residue as an intermediate protection layer to support the TiO2 framework and mesostructures during the crystallization. Other transition metal ion dopants (such as Cr, Ni and Co) can be facilely incorporated into the TiO2 frameworks by co-assembly of these metal acetylacetone precursors during the EISA process. The obtained TiO2 thin film possesses an ordered monoclinic mesostructure distorted from a (110)-oriented primitive cubic structure, uniform and tunable large pores of 10–30 nm, a large surface area of ∼100 m2 g−1 and a high crystallinity anatase wall. The film thickness can be well controlled from 150 nm to several microns to tune the absorption, with the capability of generating free-standing film morphologies. Furthermore, this designed architecture allows for effective post-deposition of other small-bandgap semiconductor nanomaterials inside the large, open and interconnecting mesopores, leading to significantly improved solar absorption and photoconversion. As a proof-of-concept, we demonstrate that the photoanodes made of 4.75 μm thick mesoporous TiO2 film with deposited cadmium sulfide quantum dots exhibit excellent performance in PEC water splitting, with an optimized photocurrent density of 6.03 mA cm−2 and a photoconversion efficiency of 3.9%. These multi-layered mesoporous TiO2-based thin films can serve as a unique architecture for PEC and other solar energy conversion and utilization.

Electrochemical determination of olmesartan medoxomil using hydrothermally prepared nanoparticles composed SnO2-Co3O4 nanocubes in tablet dosage forms.

Low-dimensional nanoparticles composed SnO(2)-Co(3)O(4) nanocubes (NCs) were prepared by a hydrothermal method using reducing agents. The doped nanomaterials were investigated by UV/vis, powder X-ray diffraction, FT-IR, energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy, and field-emission scanning electron microscopy. They were deposited on a silver electrode (AgE, surface area, 0.0216 cm(2)) to give a drug sensor with a fast response towards Olmesartan medoxomil (OSM) in 0.1 mol L(-1) phosphate buffer-phases. The sensor also exhibits higher sensitivity, long-term stability, and enhanced electrochemical response. The calibration plot is linear (r(2)=0.9948) over the 0.28 nmol L(-1)-1.4 μM OSM concentration range. The sensitivity is ~2.083 μA cm(-2) mmol L(-1) and the detection limit is 0.17 nmol L(-1) (at an SNR of 3). We discuss the possible potential uses of this nanoparticles doped semiconductor NCs in terms of drug sensing, which could also be employed for the determination of drugs in quality control of formulation.

Highly sensitive and stable phenyl hydrazine chemical sensors based on CuO flower shapes and hollow spheres

Chemical sensors are needed to develop efficient sensing systems with high flexibility, and low capital cost for controlled recognition of analytes. Herein, we report a highly sensitive, low cost, simple chemical sensor based on flower shape and hollow sphere CuO. Following the precipitation process, FESEM images revealed that CuO nanosheets are grown in high density and organized in a proper manner to give a flower shape structure; however, following the hydrothermal method in the presence of urea, the cage like micro structures CuO hollow spheres have been discovered. XRD revealed that the grown CuO has a single-crystalline phase of a monoclinic system. The resistivity of CuO hollow spheres (1.93 × 106 Ω m) is ∼100 times higher than flower shape CuO (2.2 × 104 Ω m). The prepared CuO flower shapes and hollow spheres have been evaluated for the detection and quantification of phenyl hydrazine. The findings indicate that CuO hollow spheres and flowers exhibited good sensitivity (0.578 and 7.145 μA cm−2 mM−1) and a lower limit of detection (LOD = 2.4 mM) with a linear dynamic range (LDR) of 5.0 μM to 10.0 mM and rapid assessment of the reaction kinetics (in the order of seconds). The designed flower shape CuO sensing system is 12 times more sensitive than CuO hollow spheres. To the best of our knowledge, the measured sensitivity ∼ 7.145 μA cm−2 mM−1 of CuO flower shapes is found to be among the highest sensitivity values reported for phenyl hydrazine up to now.

Hierarchical Cu2S Microsponges Constructed from Nanosheets for Efficient Photocatalysis

Owing to their scientifi c and technological importance, tailored synthesis of inorganic crystals with exposed high active facets has intensively been studied. [ 1 ] In principle, the percentage of the specially exposed facet and the surface area of the nanocrystals could be maximized by reducing the thickness along the particular crystallographic axis and increasing the 2D lateral size of the planes. In this regard, Lu et al. have fi rst prepared the anatase TiO 2 single-crystals with 47% of highly active (001) facets by using hydrofl uoric acid (HF) as a capping agent to prevent their growth along the [001] direction. [ 2 ] More recently, Lou et al. have also demonstrated that ultrathin anatase TiO 2 nanosheets ( ∼ 3 nm in thickness and a few hundred nanometer in lateral size) with nearly 100% of exposed (001) facets can be obtained by using diethylenetriamine (DETA) to prohibit the growth of titania along the [001] direction. [ 3 ]

Fabrication of a methanol chemical sensor based on hydrothermally prepared α-Fe2O3 codoped SnO2 nanocubes

We have prepared calcined α-Fe(2)O(3) codoped SnO(2) nanocubes (NCs) by a hydrothermal method using reducing agents in alkaline medium. The codoped NCs were characterized by UV/vis, FT-IR, and Raman spectroscopy, powder X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM). They were deposited on a silver electrode (AgE, surface area, 0.0216 cm(2)) to give a sensor with a fast response towards methanol in liquid phase. The sensor also exhibits good sensitivity and long-term stability, and enhanced electrochemical response. The calibration plot is linear (r(2)=0.9809) over the 0.25 mmol L(-1) to 0.25 mol L(-1) methanol concentration range. The sensitivity is ∼5.79 μA cm(-2)mM(-1), and the detection limit is 0.16 ± 0.02 mmol L(-1) (signal-to-noise ratio, at a SNR of 3). We also discuss possible future prospective uses of this codoped semiconductor nanomaterial in terms of chemical sensing.

Selective determination of gold(III) ion using CuO microsheets as a solid phase adsorbent prior by ICP-OES measurement

We have prepared calcined CuO microsheets (MSs) by a wet-chemical process using reducing agents in alkaline medium and characterized by UV/vis., fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM) etc. The detailed structural, compositional, and optical characterizations of the MSs were evaluated by XRD pattern, FT-IR, X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy, respectively which confirmed that the obtained MSs are well-crystalline CuO and possessed good optical properties. The CuO MSs morphology was investigated by FESEM, which confirmed that the calcined nanomaterials were sheet-shaped and grown in large-quantity. Here, the efficiency of the CuO MS was applied for a selective adsorption of gold(III) ion prior to its detection by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of CuO MSs towards various metal ions, including Au(III), Cd(II), Co(II), Cr(III), Fe(III), Pd(II), and Zn(II) was analyzed. Based on the adsorption isotherm study, it was confirmed that the selectivity of MSs phase was mostly towards Au(III) ion. The static adsorption capacity for Au(III) was calculated to be 57.0 mg g(-1). From Langmuir adsorption isotherm, it was confirmed that the adsorption process was mainly monolayer-adsorption onto a surface containing a finite number of adsorption sites.

Chemo-sensors development based on low-dimensional codoped Mn2O3-ZnO nanoparticles using flat-silver electrodes

BackgroundSemiconductor doped nanostructure materials have attained considerable attention owing to their electronic, opto-electronic, para-magnetic, photo-catalysis, electro-chemical, mechanical behaviors and their potential applications in different research areas. Doped nanomaterials might be a promising owing to their high-specific surface-area, low-resistances, high-catalytic activity, attractive electro-chemical and optical properties. Nanomaterials are also scientifically significant transition metal-doped nanostructure materials owing to their extraordinary mechanical, optical, electrical, electronic, thermal, and magnetic characteristics. Recently, it has gained significant interest in manganese oxide doped-semiconductor materials in order to develop their physico-chemical behaviors and extend their efficient applications. It has not only investigated the basic of magnetism, but also has huge potential in scientific features such as magnetic materials, bio- & chemi-sensors, photo-catalysts, and absorbent nanomaterials.ResultsThe chemical sensor also displays the higher-sensitivity, reproducibility, long-term stability, and enhanced electrochemical responses. The calibration plot is linear (r2 = 0.977) over the 0.1 nM to 50.0 μM 4-nitrophenol concentration ranges. The sensitivity and detection limit is ~4.6667 μA cm-2 μM-1 and ~0.83 ± 0.2 nM (at a Signal-to-Noise-Ratio, SNR of 3) respectively. To best of our knowledge, this is the first report for detection of 4-nitrophenol chemical with doped Mn2O3-ZnO NPs using easy and reliable I-V technique in short response time.ConclusionsAs for the doped nanostructures, NPs are introduced a route to a new generation of toxic chemo-sensors, but a premeditate effort has to be applied for doped Mn2O3-ZnO NPs to be taken comprehensively for large-scale applications, and to achieve higher-potential density with accessible to individual chemo-sensors. In this report, it is also discussed the prospective utilization of Mn2O3-ZnO NPs on the basis of carcinogenic chemical sensing, which could also be applied for the detection of hazardous chemicals in ecological, environmental, and health care fields.

An assessment of zinc oxide nanosheets as a selective adsorbent for cadmium

Zinc oxide nanosheet is assessed as a selective adsorbent for the detection and adsorption of cadmium using simple eco-friendly extraction method. Pure zinc oxide nanosheet powders were characterized using field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The zinc oxide nanosheets were applied to different metal ions, including Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III). Zinc oxide nanosheets were found to be selective for cadmium among these metal ions when determined by inductively coupled plasma-optical emission spectrometry. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on zinc oxide nanosheets.

Fabrication of smart chemical sensors based on transition-doped-semiconductor nanostructure materials with µ-chips.

Transition metal doped semiconductor nanostructure materials (Sb2O3 doped ZnO microflowers, MFs) are deposited onto tiny µ-chip (surface area, ∼0.02217 cm2) to fabricate a smart chemical sensor for toxic ethanol in phosphate buffer solution (0.1 M PBS). The fabricated chemi-sensor is also exhibited higher sensitivity, large-dynamic concentration ranges, long-term stability, and improved electrochemical performances towards ethanol. The calibration plot is linear (r2 = 0.9989) over the large ethanol concentration ranges (0.17 mM to 0.85 M). The sensitivity and detection limit is ∼5.845 µAcm−2mM−1 and ∼0.11±0.02 mM (signal-to-noise ratio, at a SNR of 3) respectively. Here, doped MFs are prepared by a wet-chemical process using reducing agents in alkaline medium, which characterized by UV/vis., FT-IR, Raman, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM) etc. The fabricated ethanol chemical sensor using Sb2O3-ZnO MFs is simple, reliable, low-sample volume (<70.0 µL), easy of integration, high sensitivity, and excellent stability for the fabrication of efficient I–V sensors on μ-chips.

Fabrication of highly sensitive ethanol sensor based on doped nanostructure materials using tiny chips

Doped CuO–Fe2O3 nanocubes (NCs) are prepared via a facile wet-chemical process using active reactant precursors with reducing agents in high pH medium (pH > 10). The NCs are totally characterized in detail using various methods, such as FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), dynamic light scattering (DLS), powder XRD, UV/vis spectroscopy, FESEM coupled XEDS, FE-SEM, etc. A thin-layer of NCs is deposited on tiny chips (surface area, ∼0.02217 cm2) to fabricate a selective ethanol sensor with short response time in liquid-phase medium. The fabricated chemi-sensor also exhibits higher sensitivity, large dynamic concentration ranges, long-term stability, and improved electrochemical performance towards ethanol. The calibration plot is linear (r2 = 0.9937) over a wide ethanol concentration range (0.1 nM to 0.1 mM). The sensitivity and detection limit are ∼7.258 μA cm−2 mM−1 and ∼0.08 ± 0.02 mM (SNR, signal-to-noise ratio of 3), respectively. This novel effort establishes a well-organized way of developing efficient nanomaterial-based sensors for toxic pollutants in environmental and health-care fields on large scales.