Hybrid supercapacitors (battery-supercapacitor hybrid devices, HSCs) deliver high energy within seconds (excellent rate capability) with stable cyclability. One of the key limitations in developing high-performance HSCs is imbalance in power capability between the sluggish Faradaic lithium-intercalation anode and rapid non-Faradaic capacitive cathode. To solve this problem, we synthesize Nb2O5@carbon core-shell nanocyrstals (Nb2O5@C NCs) as high-power anode materials with controlled crystalline phases (orthorhombic (T) and pseudohexagonal (TT)) via a facile one-pot synthesis method based on a water-in-oil microemulsion system. The synthesis of ideal T-Nb2O5 for fast Li(+) diffusion is simply achieved by controlling the microemulsion parameter (e.g., pH control). The T-Nb2O5@C NCs shows a reversible specific capacity of ∼180 mA h g(-1) at 0.05 A g(-1) (1.1-3.0 V vs Li/Li(+)) with rapid rate capability compared to that of TT-Nb2O5@C and carbon shell-free Nb2O5 NCs, mainly due to synergistic effects of (i) the structural merit of T-Nb2O5 and (ii) the conductive carbon shell for high electron mobility. The highest energy (∼63 W h kg(-1)) and power (16 528 W kg(-1) achieved at ∼5 W h kg(-1)) densities within the voltage range of 1.0-3.5 V of the HSC using T-Nb2O5@C anode and MSP-20 cathode are remarkable.
Image Formation: The film on the silicon wafer, prepared by the same method as for the fluorescence measurements, was covered with a photomask and irradiated with 254 nm UV light (8 J cm ±2 ). The irradiated film on the silicon wafer was dipped in a 5 mM fluorescamine solution and subsequently dried at 50 C for 4 h. The fluorescence image was observed by fluorescence microscopy.Quantum Yield Measurements: The relative quantum yields of the fluorescamine-treated copolymer solution and film were determined using a previously reported procedure [27]. The quantum yields of a Rhodamine B solution and a MEH-PPV film are 0.45 and 0.1, respectively [27,28]. Photoluminescence (PL) spectra were recorded using an ACTON spectrometer (SpectraPro-300i) connected to a photomultiplier tube (Acton Research, PD-438), with a xenon lamp as the excitation source that was connected to another monochromator One way of utilizing zeolite microcrystals for advanced materials is to organize them into ordered functional entities. [1] To this end, we have explored methods of organizing them in the form of closely packed and uniformly aligned monolayers on various substrates through large numbers of interconnecting molecular linkages between each microcrystal and the substrate.[2±14] The produced aligned monolayers of zeolite crystals can serve as useful seed crystals for the preparation of aligned continuous zeolite films that may find many useful applications. [15,16] So far, reflux and stirring' has been the only way to promote the reaction between functional groups tethered to the zeolite crystals and a substrate, to obtain monolayer assembly of the microcrystals on a substrate. Under these conditions, the typically required reaction time for achieving close to 100 % degree of coverage (DOC, defined as the percentage of the attached amount of crystals in the monolayer with respect to the maximum attached amount) of the substrate surface with the crystals is 24 h. Accordingly, it requires more than 24 h to achieve high degrees of lateral close packing (degree of close packing, DCP) between the crystals. We now report that ultrasound-aided strong agitation leads to a more than 10 3 -fold increase in the rate of achieving »100 % DOC and DCP. We discovered the above phenomenon during an investigation into the effect of the mode of reaction promotion (MRP) on DOC and DCP during the monolayer assembly of silicalite (SL) crystals on glass, by employing the previously reported method for the formation of covalent linkages between surface hydroxyl groups of bare zeolite crystals and 3-chloropro-COMMUNICATIONS
Silicalite-1 films (thickness = 400 nm) supported on both sides of glass plates (SL/G) were prepared, and hemicyanine dyes (HC-n) with different alkyl chain lengths (n, n = 3, 6, 9, 12, 15, 18, 22, and 24) were included into the silicalite-1 films by dipping SL/Gs into each methanol solution of HC-n (1 mM) for 1 d. The included numbers of HC-n per channel (N(C)) generally decreased with increasing n; that is, they were 6.4, 23.1, 15.4, 8.2, 5.7, 3.5, 0.9, and 1.2 molecules per channel, respectively. The d(33) value gradually increased with increasing n but decreased when n > 18; that is, they were 1.12, 0.50, 2.25, 3.59, 4.99, 5.30, 1.71, and 2.57 pm V(-1), respectively. However, d(33)/N(C) progressively increased with increasing n. The d(31) values were approximately 100 times smaller than the corresponding d(33) values, and the average d(33)/d(31) ratio was 109, which is higher than those of Langmuir-Blodgett (LB) films and poled polymers of nonlinear optical (NLO) dyes, by approximately 2-5 and approximately 30-50 times, respectively. The estimated average tilted angle of the dyes with respect to the channel direction was 7.7 degrees, and the calculated average order parameter was 0.97, which is approximately 480 times higher than the values observed from poled polymers. The degree of uniform alignment (DUA) generally increased with increasing n. The progressive increase of both DUA and d(33)/N(C) with n is attributed to the increase in the tendency of HC-n to enter hydrophobic silicalite-1 channels with the hydrophobic alkyl chain first. A more than 134-fold increase in DUA was observed upon increasing n from 6 to 24. The DUA of HC-24 in the silicalite-1 film reached close to 1. Although the observed d(33) values were lower than those of the LB films of NLO dyes due to very small dye densities of the silicalite films, this methodology bears a great potential to be developed into the methods for preparing practically viable NLO films.
The organization of micrometer‐sized zeolite (ZSM‐5) crystals into micropatterned, uniformly oriented monolayers on glass (see SEM image) is reported. The simple yet highly versatile process, which has many advantages over conventional molding and heating methods, is based on the formation of covalent links by microcontact printing.
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