A large quantity of nanosized ZnO tubular structures was prepared using a very simple thermal evaporation of mixed Zn–ZnO powders under a wet oxidation condition. The ZnO nanotubes have a hollow core with crystalline wall of 8–20 nm in thickness. Optical properties of ZnO nanotubes were studied at room temperature. Raman peaks arising from the ZnO nanotubes were analyzed, which correspond well to that of the bulk ZnO sample. The photoluminescence measurements of ZnO nanotubes revealed an intensive UV peak at 377 nm corresponding to the free exciton emission, and a broad peak at about 500 nm arising from defect-related emission.

A high conductive 2D COF polyporphyrin (TThPP) linked by 4-thiophenephenyl groups was synthesized through an in situ chemical oxidative polymerization on the surface of copper foil. The TThPP films were used as the anode of lithium-ion battery, which exhibited high specific capacities, excellent rate performances, and long cycle lives due to the alignment of 2D polyporphyrin nanosheets, and they (i) can highly efficiently adsorb Li atoms, (ii) have short-ended paths for the fast lithium ion diffusion, and (iii) open nanopores holding electrolyte. The reversible capacity is up to 666 mAh/g. This is the first example of an organic 2D COF for an anode of lithium-ion battery and represents an important step toward the use of COFs in the next-generation high-performance lithium-ion battery.

Magnetic nanoparticles that can be transported in subsurface reservoirs at high salinities and temperatures are expected to have a major impact on enhanced oil recovery, carbon dioxide sequestration, and electromagnetic imaging. Herein we report a rare example of steric stabilization of iron oxide (IO) nanoparticles (NPs) grafted with poly(2-acrylamido-2-methylpropanesulfonate-co-acrylic acid) (poly(AMPS-co-AA)) that not only display colloidal stability in standard American Petroleum Institute (API) brine (8% NaCl + 2% CaCl2 by weight) at 90 °C for 1 month but also resist undesirable adsorption on silica surfaces (0.4% monolayer NPs). Because the AMPS groups interacted weakly with Ca(2+), they were sufficiently well solvated to provide steric stabilization. The PAA groups, in contrast, enabled covalent grafting of the poly(AMPS-co-AA) chains to amine-functionalized IO NPs via formation of amide bonds and prevented polymer desorption even after a 40,000-fold dilution. The aforementioned methodology may be readily adapted to stabilize a variety of other functional inorganic and organic NPs at high salinities and temperatures.

in aqueous systems due to their limited solubility in water and well distributed redox potentials. [ 2,[13][14][15][16] In contrast, nonaqueous systems can accommodate organic molecules with good solubility and electrochemical compatibility. [ 17 ] Redox active materials are the most important component for nonaqueous redox fl ow batteries (NRFBs), which dictate the overall performance. The desired materials need well separated anodic and cathodic reversible intrinsic redox reactions to accommodate the reversible electron transfer processes of the catholytes and anolytes. Two options can be considered for the material development. First, the same molecular species could be used on both sides of the NRFBs. This kind of molecules, or so-called universal molecules, should have both anodic and cathodic types of reversible redox reactions within one molecular structure so that they can function both as catholyte and anolyte materials. Vanadium ions [18][19][20] and acetylacetonate-based metal complexes [ 21 ] are examples employing this approach. The most obvious advantage is the mitigation of membrane crossover issue, a major issue for capacity decay of fl ow batteries. [ 22 ] However, such universal molecules, especially organic molecules, usually have complex structures, thus leading to high molecular weight, not favorable for the energy and cost considerations. The second option is to use different molecules as catholyte and anolyte materials, respectively. These molecules are single functional molecules, since they have only one type of intrinsic reversible redox reaction (either anodic or cathodic). In this category, since the intrinsic redox reactions can be fully utilized during the charging and discharging processes, higher energy density can be achieved. Single functional molecules usually have simple chemical structures compared to universal ones, which is favorable for the effi cient molecular design and synthesis.One example of the single functional cathlyte molecules is 2,5-di-tert -butyl-1,4-bis(2-methoxyethoxy)benzene (DBBB), as shown in Figure 2 , which is a redox active organic molecule discovered during our recent investigation of the redox shuttles for the lithium ion batteries. [ 15 ] DBBB is built upon the dimethoxydi-tert -butyl-benzene platform and is a very electrochemically reversible (3.9 V vs Li/Li + ), stable and soluble molecule that later found its way to be a promising catholyte candidate in an all organic NRFB. [ 2 ] Redox shuttle molecules, initially proposed for the overcharge protection for lithium ion batteries, have many similar requirements as catholyte molecules, such as good electrochemical reversibility, high redox potential, good solubility, and excellent electrochemical stability. The knowledge of building reversible redox active molecules is precious to the catholyte molecule development, which could serve as the starting point and dramatically shorten the initial exploration Redox fl ow batteries (RFBs) have been increasingly recognized to have signifi cant potentials for ...

The transport of engineered nanoparticles in porous media is of interest in numerous applications including electromagnetic imaging of subsurface reservoirs, enhanced oil recovery, and CO 2 sequestration. A series of poly(2-acrylamido-2methyl-1-propanesulfonic acid-co-acrylic acid) (poly(AMPS-co-AA)) random copolymers were grafted onto iron oxide (IO) nanoparticles (NPs) to provide colloidal stability in American Petroleum Institute (API) standard brine (8 wt/wt % NaCl and 2 wt/wt %CaCl 2 , anhydrous basis). A combinatorial approach, which employed grafting poly(AMPS-co-AA) with wide ranges of compositions onto platform amine-functionalized IO NPs via a 1-ethyl-3-(3-(dimethylamino)propyl)carbondiimidecarbondiimide (EDC) catalyzed amidation, was used to screen a large number of polymeric coatings. The ratio of AMPS/AA was varied from 1:1 to 20:1 to balance the requirements of particle stabilization, low adsorption/retention (provided by 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)), and permanent attachment of stabilizer (provided by acrylic acid (AA)). The resulting nanoparticles remained stable in aqueous suspension despite the extremely high salinity conditions and exhibited low adsorption on silica microspheres. Greater than 91% of applied IO-NP mass was transported through columns packed quartz sand, and the mobility of IO NP increased by ca. 6% when the AMPS to AA ratio was increased from 1:1 to 3:1, consistent with batch adsorption data. In both static batch reactor and dynamic column tests, the observed attachment of IO NPs was attributed to divalent cation (Ca 2+ ) mediated bridging and hydrophobic interactions. Collectively, the rapid, high throughput combinatorial approach of grafting and screening (via batch adsorption) provides for the development of high mobility NPs for delivery in various porous media under high salinity conditions.

Reversible conductance transitions are demonstrated on the molecular scale in a complex of 3-nitrobenzal malononitrile and 1, 4-phenylenediamine, by application of local electric field pulses. Both macroscopic and local current-voltage (I/V) measurements show similar electrical bistability behavior. The mechanism of the electrical bistability is discussed.

Development of simple, cost-effective, and sensitive fluorescence-based sensors for explosives implies broad applications in homeland security, military operations, and environmental and industrial safety control. However, the reported fluorescence sensory materials (e.g., polymers) usually respond to a class of analytes (e.g., nitroaromatics), rather than a single specific target. Hence, the selective detection of trace amounts of trinitrotoluene (TNT) still remains a big challenge for fluorescence-based sensors. Here we report the selective detection of TNT vapor using the nanoporous fibers fabricated by self-assembly of carbazole-based macrocyclic molecules. The nanoporosity allows for time-dependent diffusion of TNT molecules inside the material, resulting in further fluorescence quenching of the material after removal from the TNT vapor source. Under the same testing conditions, other common nitroaromatic explosives and oxidizing reagents did not demonstrate this postexposure fluorescence quenching; rather, a recovery of fluorescence was observed. The postexposure fluorescence quenching as well as the sensitivity is further enhanced by lowering the highest occupied molecular orbital (HOMO) level of the nanofiber building blocks. This in turn reduces the affinity for oxygen, thus allocating more interaction sites for TNT. Our results present a simple and novel way to achieve detection selectivity for TNT by creating nanoporosity and tuning molecular electronic structure, which when combined may be applied to other fluorescence sensor materials for selective detection of vapor analytes.

A high performance Li-S battery with novel fluoroether-based electrolyte was reported. The fluorinated electrolyte prevents the polysulfide shuttling effect and improves the Coulombic efficiency and capacity retention of the Li-S battery. Reversible redox reaction of the sulfur electrode in the presence of fluoroether TTE was systematically investigated. Electrochemical tests and post-test analysis using HPLC, XPS, and SEM/EDS were performed to examine the electrode and the electrolyte after cycling. The results demonstrate that TTE as a cosolvent mitigates polysulfide dissolution and promotes conversion kinetics from polysulfides to Li2S/Li2S2. Furthermore, TTE participates in a redox reaction on both electrodes, forming a solid electrolyte interphase (SEI) which further prevents parasitic reactions and thus improves the utilization of the active material.