The effect of Mg(2+) on hydrothermal formation of α-CaSO4·0.5H2O whiskers with high aspect ratios was investigated in this paper. α-CaSO4·0.5H2O whiskers with a preferential growth along the c axis and an average aspect ratio up to 370 were synthesized using hydrothermal treatment of CaSO4·2H2O precursor in the presence of 1.97 × 10(-3) mol·L(-1) MgCl2. The preferential adsorption of Mg(2+) on the negative (200), (400), and (020) facets was confirmed by EDS, XPS, and zeta potential measurements. ATR-FTIR analysis revealed the ligand adsorption of Mg(2+) on the surface of α-CaSO4·0.5H2O. The doping of Mg(2+) in α-CaSO4·0.5H2O whiskers was confirmed by the XRD analysis. The experimental results indicated that the adsorption and doping of Mg(2+) promoted the 1-D growth of α-CaSO4·0.5H2O whiskers, leading to the formation of whiskers with high aspect ratios.
ZnO hierarchical structures assembled by tunable nanoscale building blocks such as nanorods, nanosheets and nanoparticles were synthesized from dilution-induced supersaturated solutions.
This paper reports the zinc interstitial-induced
room temperature
ferromagnetism (RT-FM) in undoped ZnO nanorods synthesized by aging
ε-Zn(OH)2 precursor in 0–2 mol·L–1 NaOH at 80 °C for 10.0 h. The variations of
the defect states and ferromagnetism of the ZnO nanorods with NaOH
concentration were investigated by X-ray diffraction, Raman scattering,
photoluminescence, electron spin resonance, X-ray photoelectron spectroscopy,
and superconducting quantum interference device so as to identify
the origin of RT-FM. The experimental results revealed that the increase
of the NaOH concentration led to the increase of the oxygen-related
defects but the decrease of the zinc interstitials in association
with the magnetization value. A direct correlation between the ferromagnetism
and the relative concentration of the zinc interstitials was established,
which indicated that the zinc interstitials may play an important
role in mediating the RT-FM in the undoped ZnO nanorods.
Nanomaterials have shown tremendous potentials to impact the broad field of biological sensing. Nanomaterials, with extremely small sizes and appropriate surface modifications, allow intimate interaction with target biomolecules. [...]
We report a novel room temperature methanol sensor comprised of gold nanoparticles covalently attached to the surface of conducting copolymer films. The copolymer films are synthesized by oxidative chemical vapor deposition (oCVD), allowing substrate-independent deposition, good polymer conductivity and stability. Two different oCVD copolymers are examined: poly(3,4-ethylenedioxythiophene-co-thiophene-3-aceticacid)[poly(EDOT-co-TAA)] and poly(3,4-ehylenedioxythiophene-co-thiophene-3-ethanol)[poly(EDOT-co-3-TE)]. Covalent attachment of gold nanoparticles to the functional groups of the oCVD films results in a hybrid system with efficient sensing response to methanol. The response of the poly(EDOT-co-TAA)/Au devices is found to be superior to that of the other copolymer, confirming the importance of the linker molecules (4-aminothiophenol) in the sensing behavior. Selectivity of the sensor to methanol over n-pentane, acetone, and toluene is demonstrated. Direct fabrication on a printed circuit board (PCB) is achieved, resulting in an improved electrical contact of the organic resistor to the metal circuitry and thus enhanced sensing properties. The simplicity and low fabrication cost of the resistive element, mild working temperature, together with its compatibility with PCB substrates pave the way for its straightforward integration into electronic devices, such as wireless sensor networks.
The influence of the activity of calcium sulfate dihydrate (CaSO 4 ⋅2H 2 O) on the hydrothermal formation of CaSO 4 ⋅0.5H 2 O whiskers was investigated in this paper, using commercial CaSO 4 ⋅2H 2 O as the raw material. The experimental results indicated that the activity of CaSO 4 ⋅2H 2 O was improved after calcination of the commercial CaSO 4 ⋅2H 2 O at 150 ∘ C for 6.0 h followed by hydration at room temperature for 1.0 h, corresponding to the decrease of the agglomerated particle sizes from 29.7 m to 15.1 m, the increase of the specific surface areas (BET) from 4.75 m 2 ⋅ g −1 to 19.12 m 2 ⋅ g −1 and the grain sizes from 95 nm to 40 nm. The active CaSO 4 ⋅2H 2 O produced by the calcination-hydration treatment favored the hydrothermal dissolution of CaSO 4 ⋅2H 2 O, promoting the formation of hemihydrate calcium sulfate (CaSO 4 ⋅0.5H 2 O) whiskers with high aspect ratios.
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