Green upconversion emission from hexagonal‐phase NaYF4:Yb, Er3+ phosphors can be directly observed with the naked eye. Powders with controlled size and morphology can be synthesized in ethanol and show a minimal decrease in luminescence intensity after 24 h (see Figure). The intense upconversion emission suggests good crystallinity of the materials, which may be used in biological labeling.
Complex rare earth fluoride (NaRF(4), R = Ce,Y,Gd) nanocrystals of 30-50 nm were synthesized by hydrothermal and solvothermal techniques. The size, morphology and phase transition of the complex rare earth fluorides are discussed as the effects of different solvents, reaction time and temperature. Hexagonal phase NaRF(4) nanocrystals with good dispersibility can be prepared in the presence of EDTA using ethanol as the solvent. After doping with Yb(3+), Er(3+); Yb(3+), Tm(3+), and Eu(3+), some typical up-conversion and down-conversion photoluminescence was characterized and discussed.
The initial growth of the nacreous layer is crucial for comprehending the formation of nacreous aragonite. A flat pearl method in the presence of the inner-shell film was conducted to evaluate the role of matrix proteins in the initial stages of nacre biomineralization in vivo. We examined the crystals deposited on a substrate and the expression patterns of the matrix proteins in the mantle facing the substrate. In this study, the aragonite crystals nucleated on the surface at 5 days in the inner-shell film system. In the film-free system, the calcite crystals nucleated at 5 days, a new organic film covered the calcite, and the aragonite nucleated at 10 days. This meant that the nacre lamellae appeared in the inner-shell film system 5 days earlier than that in the film-free system, timing that was consistent with the maximum level of matrix proteins during the first 20 days. In addition, matrix proteins (Nacrein, MSI60, N19, N16 and Pif80) had similar expression patterns in controlling the sequential morphologies of the nacre growth in the inner-film system, while these proteins in the film-free system also had similar patterns of expression. These results suggest that matrix proteins regulate aragonite nucleation and growth with the inner-shell film in vivo.
Hydrogen peroxide (H 2 O 2 ), the most desired green oxidant, [1] is almost exclusively produced by an anthraquinone (AQ) process. [2] Direct oxidation of H 2 with O 2 has long been considered an ideal alternative for H 2 O 2 production. [3] Extensive studies have been done on direct H 2 O 2 synthesis from a H 2 /O 2 mixture. To achieve high efficiency, direct H 2 O 2 synthesis is generally performed in acidified solvent over supported noble-metal catalysts (Au, Pd, Au-Pd, and Pd-Pt). [4][5][6][7][8][9][10][11] However, the direct synthesis of H 2 O 2 from a H 2 /O 2 mixture catalyzed by metals is quite hazardous, and it is very difficult to directly obtain high-purity and high-concentration H 2 O 2 .Research [12,13] published in the 1960s has demonstrated that H 2 O 2 can be generated in H 2 /O 2 non-equilibrium plasma through free-radical reactions in the absence of any catalyst or chemical. However, this plasma method has not yet drawn much attention, owing to low H 2 O 2 yield (less than ca. 5 %) and safety concerns about the discharge-triggered H 2 /O 2 reaction. [12,14] The content of O 2 must be strictly controlled below 4 mol % in order to prevent explosion and ignition. [15] Our previous research [16] showed that the structure of the plasma reactor played an important role in the direct synthesis of H 2 O 2 . A H 2 /O 2 mixture containing 3 mol % of O 2 reaches 100 % O 2 conversion, but the H 2 O 2 selectivity is only 3.5 % (based on O 2 ) in a single dielectric barrier discharge (SDBD) plasma reactor with a naked metal highvoltage (HV) electrode and an aqueous grounding electrode. On the other hand, 57.8 % O 2 conversion and 56.3 % H 2 O 2 selectivity (based on O 2 ) can be obtained by using a double dielectric barrier discharge (DDBD) plasma reactor with a pyrex-covered metal HV electrode (the pyrex cover acts as an additional dielectric barrier) and an aqueous grounding electrode. Although the selectivity has been greatly improved, the safety concerns and low efficiency, owing to low O 2 content, are still big challenges.Herein, we report an experimental realization of controllable H 2 /O 2 combustion processes by an optimized plasma reactor. High purity (Grade 1 electronic grade H 2 O 2 according to the SEMI standard) and highly concentrated H 2 O 2 solution (ca. 60 wt %) can be directly produced from a H 2 /O 2 mixture without explosion. These results suggest a different mechanism from conventional H 2 /O 2 combustion processes in the H 2 /O 2 plasma reaction. As shown in Scheme 1, the electron activation of H 2 into H is responsible for H 2 O 2 formation. However, the electron activation of O 2 into O and O 2 * (vibrational and electronic excited states) leads to H 2 O formation and explosion of the H 2 /O 2 mixture. Moreover, low-electron-density H 2 /O 2 plasma leads to a low degree of H 2 and O 2 activation, which plays quite a significant role in producing H 2 O 2 and controlling H 2 /O 2 combustion.The plasma reactor used in our experiments is a double aqueous electrode DDBD reactor (Support...
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