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•Rhombhohedron and plate-like nanostructures are synthesized by hydrothermal method.•The HC is strongly enhanced with changing of the particle morphology.•The Morin transition is ...slightly morphology-dependent.•The nanoplates have higher T2 relaxation than rhombohedrons.
Hematite nanorhombohedrons and nanoplates have been prepared through a hydrothermal synthesis process. The nanoplates possess width of 100 nm and thickness of 30 nm whereas hematite nanorhombohedrons (cube-like particles) have an edge length of 50 nm. The magnetization show that the Morin transitions of the samples occur at nearly the same temperature showing slightly shape-dependent magnetic properties (TM(P) = 242 K (plates) and TM(R) = 221 K (rhombohedrons). The nanorhombohedrons exhibit hysteresis properties with low coercivity HC(R) = 22 Oe at room temperature, whereas nanoplates show much higher coercivity (∼24 times higher) HC(P) = 522 Oe and strongly shape-dependent magnetic properties. The coercivity below the Morin transition is also observed for nanorhombohedrons HC(R) = 178 Oe and for nanoplates HC(P) = 2280 Oe. The transverse relaxivity rate R2 (1/T2) measured on 15.2 T magnetic resonance imaging (MRI) scanner was higher for nanoplates than for nanorhombohedrons (12.63 vs 10.72 mM-1s-1). The properties of the samples are discussed in relation to the particle shape.
•A mixture of PVP and citric acid was utilized as fuel for solution combustion of ZnO powders.•Honeycomb-like structure with the thickness of 48 nm was obtained at φ = 0.5.•Specific surface area ...increased from 19 to 141 m2/g by an addition in fuel content.•ZnO powders prepared at φ = 1 exhibits good photodegradation of MB, Rh B, and MO under ultraviolet light irradiation.
Single phase zinc oxide (ZnO) powders were obtained via solution combustion method using various amounts of mixture of polyvinylpyrrolidone and citric acid as fuel. The powders had honeycomb-like structure which transformed to spongy structure accompanied by the increase of specific surface area from 19 to 141 m2/g with the increase of fuel content. The methylene blue, methyl orange and rhodamine B dyes were photodegraded in the presence of ZnO powders under ultraviolet irradiation. The highest photodegradation (94%) was obtained for methylene blue by ZnO powders prepared at fuel to oxidant ratio of 1. However, the photodegradation decreased to 52 and 88% for methyl orange and rhodamine B dyes, respectively.
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•Non-noble metal Co was loaded on TiO2 to enhance photocatalytic H2 production.•Co loading can significantly enhance photocatalytic H2 activity.•Co can facilitate the charge ...separation and reduce overpotential of H2 evolution.
Non-noble metal Co was decorated on TiO2 nanorod by a photodeposition method to improve photocatalytic H2 production. Co particles with ca. 7 nm diameter dispersed well onto the TiO2 nanorods. Photocatalytic H2 production performance of Co/TiO2 was tested and the results showed that the photocatalytic activity was promoted by Co loading. The H2 evolution rate of 2.0 wt% Co/TiO2 (839.8 μmol ⋅ h−1) is 8.9 times of that of bare TiO2 (95 μmol ⋅ h−1), reaching 77.8% of that of 1.0 wt% Pt/TiO2 (1080μmol⋅h−1). Photoelectrochemical and PL measurements indicated that, like Pt cocatalyst, the loading of Co particles reduces the overpotential of H2 evolution as well as facilitates the transfer of photoinduced electrons from TiO2 to Co cocatalyst, thus improving the photocatalytic H2 evolution activity. The study not only provides a way to cut the cost of photocatalysts but gives an in-depth understanding of the effect of cocatalysts on enhancing photocatalytic H2 evolution activity.
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► Mesoporous WO3 nanoplate monoliths were obtained by direct templating synthesis. ► Enable effective accession of the analytic molecules for the sensor applications. ► The WO3 sensor ...exhibited a high performance to NO2 gas at low temperature.
Controllable synthesis of nanostructured metal oxide semiconductors with nanocrystalline size, porous structure, and large specific surface area is one of the key issues for effective gas sensor applications. In this study, crystalline mesoporous tungsten oxide nanoplate-like monoliths with high specific surface areas were obtained through instant direct-templating synthesis for highly sensitive nitrogen dioxide (NO2) sensor applications. The copolymer soft template was converted into a solid carbon framework by heat treatment in an inert gas prior to calcinations in air to sustain the mesoporous structure of tungsten oxide. The multidirectional mesoporous structures of tungsten oxide with small crystalline size, large specific surface area, and superior physical characteristics enabled the rapid and effective accession of analytic gas molecules. As a result, the sensor response was enhanced and the response and recovery times were reduced, in which the mesoporous tungsten oxide based gas sensor exhibited a superior response of 21,155% to 5ppm NO2. In addition, the developed sensor exhibited selective detection of low NO2 concentration in ammonia and ethanol at a low temperature of approximately 150°C.
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•Mesoporous TiO2 was prepared using an evaporation-induced self-assembly method.•The obtained TiO2 had hexagonal mesostructure with highly crystalline anatase phase.•Mesoporous TiO2 ...exhibited high sunlight-driven photocatalytic activity in dye degradation.•The charge-dependent photocatalytic behaviour of the mesoporous TiO2 was investigated.
The development of new strategies and photocatalytic materials for practical environmental solutions remains a great challenge, particularly due to the large energy demands associated with various remediation processes. In this paper, we report the fabrication of self-assembled ordered mesoporous TiO2 with highly crystalline anatase structures as well as high surface area, and characterize their photocatalytic performance on the degradation of three typical dyes, including anionic methyl orange, cationic methylene blue, and neutral rhodamine B driven merely by sunlight. The results show that the dye photodegradation strongly depends on the charging state of both mesoporous TiO2 surface and dyes, which can be adjusted by the pH value of the solutions. Such charge-dependent photocatalytic functionality of mesoporous TiO2 can thus be exploited for highly efficient and selective dye photodegradation.
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► For the first time, green synthesis of salep capped Ag nano-wedges was reported via the wet chemical synthesis method. ► Salep, a capping/shaping polysaccharide composite, resulted ...in synthesis of the Ag nano-wedges. ► Biomedical activity of the Ag nano-wedges introduces these poniard-like materials as a forceful biocide.
In the current study, for the first time, photochemical facile green synthesis of salep capped silver nano-wedges was reported via the wet chemical synthesis procedure. Sunlight-UV as an available reducing agent caused mild reduction of silver ions to the silver nano-wedges. Salep as an effective capping/shaping polysaccharide bioresource material was used in the reaction medium and caused creation of flower-like self-assembled structures of the silver nano-wedges. The formation of silver nano-wedges and their flower-like self-assembled structures was confirmed by SEM technique. Further investigations were carried out using UV–vis, FTIR, GPC and XRD data. The prepared silver nano-wedges showed potent biocidal activity against three classes of microorganisms (
Escherichia coli Gram-negative bacteria,
Staphylococcus aureus Gram-positive bacteria and
Candida albicans fungus). The silver nano-wedges prepared with this method can be introduced as real poniards because of their unique shape and antibacterial/antifungal activity and would be promising nominees for a wide range of biomedical applications.
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▶ We synthesized a Bi
2Te
y
Se
3−
y
nano-compound via a chemical synthetic process. ▶ The compound was sintered to achieve an average grain size of about 300
nm. ▶ The resulting ...sintered body showed very low thermal conductivity. It is likely caused by the vigorous phonon scattering of the nano-sized grains.
Bismuth tellurium selenide (Bi
2Te
y
Se
3−
y
) nanoparticles for thermoelectric applications are successfully prepared via a water-based chemical reaction under atmospheric conditions. The nanostructured compound is prepared using a complexing agent (ethylenediaminetetraacetic acid) and a reducing agent (ascorbic acid) to stabilize the bismuth precursor (Bi(NO
3)
3) in water and to favor the reaction with reduced sources of tellurium and selenium. The resulting powder is smaller than ca. 100
nm and has a crystalline structure corresponding to the rhombohedral Bi
2Te
2.7Se
0.3. The nanocrystalline powder is sintered via a spark plasma sintering process to obtain a sintered body composed of nano-sized grains. Important transport properties of the sintered body are measured to calculate its most important characteristic, the thermoelectric performance. The results demonstrate a relationship between the nanostructure of the sintered body and its thermal conductivity.
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Porous NaTi2(PO4)3@C nanocubes are fabricated by solvothermal/coating methods with using oleic acid as the carbon source. When studied as sodium-ion battery anode at 0.01∼3V, the ...NaTi2(PO4)3@C electrode delivers a high reserved capacity of 140 mAhg−1 at 1 Ag−1 for 1000 times.
•Porous NaTi2(PO4)3@C nanocubes are synthesized.•Oleic acid is utilized as the carbon source.•NaTi2(PO4)3@C is to be measured at 0.01–3V for SIBs.•NaTi2(PO4)3@C achieves 201 mAhg−1 at 100 mAg−1 after 100 cycles.•NaTi2(PO4)3@C delivers 140 mAhg−1 at 1 Ag−1 for 1000 times.
The NASICON-type NaTi2(PO4)3 has drawn much attention as anode material for sodium-ion batteries owing to its stable structural characteristics and low cost. Nevertheless, the insulating property of NaTi2(PO4)3 and the high working potential of about 2.1V vs. Na+/Na lead to its poor cycling stability, low rate performance as well as inferior capacity. In this work, we synthesize the porous NaTi2(PO4)3@C nanocubes by hydrothermal method and a subsequent coating process with using oleic acid as the carbon source. When utilized as the anode for sodium-ion battery in the voltage range between 0.01V and 3.0V, The as-synthesized porous NaTi2(PO4)3@C nanocubes deliver a discharge capacity of 201 mAh·g−1 at the current density of 100 mAg−1 after 100 cycles. Additionally, the reserved capacity of 140 mAh·g−1 could be achieved at the current density of 1 Ag−1 after 1000 cycles.
Structural studies of Cu-doped zirconia samples with varying Cu content have been carried out. Copper–zirconia samples containing 2–20
mol% Cu were prepared by the co-precipitation technique using ...tetramethylammonium hydroxide as the precipitating agent and calcined at 773
K in air. The powder XRD data following Rietveld refinement revealed stabilization of zirconia in both tetragonal and cubic phases for all the samples with some monoclinic impurity phase. A decrease in the unit cell parameters of the cubic and tetragonal phase indicates incorporation of copper in the zirconia lattice of both the phases. An increase in the copper concentration (up to 20
mol%) stabilizes zirconia into the cubic phase at the expense of the tetragonal phase, with a decrease in the crystallite size (6–8
nm). Rietveld refinement of the high temperature XRD data reveals that both cubic and tetragonal phases exist up to 723
K with the cubic phase dominating (80% at 723
K). At temperature higher than 723
K, cubic phase gets transformed into the tetragonal phase, which further transforms into the monoclinic phase at 1173
K. At 1173
K, copper comes out of the cubic zirconia lattice forming a separate copper oxide phase and only the tetragonal and monoclinic polymorphs of zirconia exist.
