Abdulaziz A. Bagabas

Radially oriented mesoporous TiO2 microspheres with single-crystal–like anatase walls for high-efficiency optoelectronic devices

Uniform mesoporous single-crystal TiO2 spheres with radial channels from driving orientation assembly can be used for energy storage. Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m2/g), a large pore volume (0.164 cm3/g), and highly single-crystal–like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials.

Room-temperature synthesis of zinc oxide nanoparticles in different media and their application in cyanide photodegradation

Cyanide is an extreme hazard and extensively found in the wastes of refinery, coke plant, and metal plating industries. A simple, fast, cost-effective, room-temperature wet chemical route, based on cyclohexylamine, for synthesizing zinc oxide nanoparticles in aqueous and enthanolic media was established and tested for the photodegradation of cyanide ions. Particles of polyhedra morphology were obtained for zinc oxide, prepared in ethanol (ZnOE), while spherical and some chunky particles were observed for zinc oxide, prepared in water (ZnOW). The morphology was crucial in enhancing the cyanide ion photocatalytic degradation efficiency of ZnOE by a factor of 1.5 in comparison to the efficiency of ZnOW at an equivalent concentration of 0.02 wt.% ZnO. Increasing the concentration wt.% of ZnOE from 0.01 to 0.09 led to an increase in the photocatalytic degradation efficiency from 85% to almost 100% after 180 min and a doubling of the first-order rate constant (k).

Visible-light photocatalysis on C-doped ZnO derived from polymer-assisted pyrolysis†

C-doped ZnO with a large surface area was prepared via F127-assisted pyrolysis at 500 °C and used for visible-light-responsive photocatalytic water purification. The band structure of the C-doped ZnO was investigated using valance band XPS and DFT simulation. The C-doped ZnO possessed enhanced absorption of UV and visible light, though it showed lower visible-light-responsive photocatalytic activity than ZnO because of significant recombination of photogenerated charge carriers arising from overloaded C-dopant and oxygen vacancies.

Ordered Macro/Mesoporous TiO2 Hollow Microspheres with Highly Crystalline Thin Shells for High-Efficiency Photoconversion

Well ordered, uniform 3D open macro/mesoporous TiO2 hollow microspheres with highly crystalline anatase thin shells have been successfully synthesized by a simple solvent evaporation-driven confined self-assembly method. The 3D open macro/mesoporous TiO2 hollow microspheres show high energy-conversion efficiency (up to 9.5%) and remarkable photocatalytic activity (with photodegradation of 100% for methylene blue in 12 min under UV light irradiation).

An Efficient and Low-Cost Method for the Purification of Colloidal Nanoparticles**

Efficient purification is critical to the fundamental and practical exploitation of nanoparticles in the technological domain. Whether for lighting, bio-imaging, coatings, photovoltaics, or displays, a routine, low-cost purification method that is directly applicable post-synthesis and in reuse/recycling would be of tremendous benefit to the commercialization of nanoparticle-based devices. Moreover, purification is essential to understanding the functional properties of nanoparticles, which are strongly dependent on purification history. In nonaqueous media, the most common technique for nanoparticle purification is the precipitation–dissolution method. This technique requires significant time and materials, including expensive centrifuges that do not scale well in an industrial setting. Meanwhile, the efficiency of this technique varies with the morphology and the nature of the nanoparticles, in particular giving lower yields with certain smaller and shaped nanoparticles. Other techniques, such as dialysis, ultra-filtration, and diafiltration, remain problematic as they rely on controlled-pore-size materials that are expensive and suffer from fouling. Additionally, these techniques, along with size-exclusion and high-performance liquid chromatography, have high solvent burdens and suffer from slow dynamics. Other interesting techniques involving microemulsions or particular ternary solvent systems may be difficult to generalize. Collectively, the purification techniques developed to date for nanoparticles in nonaqueous media have issues with cost, scale-up, applicability, and/or the lack of green processing. These issues are tremendous obstacles for efficient manufacturing and, by consequence, to the widespread development and implementation of nanoparticle-based technologies. Herein, we report an effective nanoparticle purification method based on reversible electrophoretic deposition, defined here as electropurification, which overcomes most the disadvantages of traditional techniques. Electrophoretic deposition is the deposition of colloidal particles through the application of an electric field, a widelyadopted industrial process used, for example, in automobile coatings. Electrophoretic deposition has also been applied in several embodiments to deposit nanoparticles such as CdSe to form permanent fixed coatings. Herein, however, we describe a method to reversibly deposit nanoparticles onto an electrode surface. We can use the reversible nature of this process, achieved through the addition of particular nonsolvents to the electrodeposition solution, to selectively collect and separate nanoparticles from unwanted impurities in solution. The collected nanoparticles are then redispersed into clean solvent. Figure 1 shows how a simple lab-scale setup can be used to separate and collect nearly 100% of oleic acid (OA)-capped CdTe nanoparticles from solution within a matter of minutes. The setup comprises two electrodes, an aluminum bar and a stainless steel mesh, placed in a glass beaker and connected by a glovebox feed-through to a DC power supply. The initial solution is the unpurified reaction media diluted with about 1.5 volume equivalents of acetone, a non-solvent. This reaction media contains the primary solvent (octadecene) and contaminants, such as excess OA, tributylphosphine (TBP), leftover precursors (cadmium oleate and Te-TBP), and reaction byproducts. Within minutes, an applied DC potential of 500 V causes the nanoparticles to collect on the aluminum anode, leaving a nearly colorless residual solution. The adsorbed nanoparticles are further washed with acetone while still on the electrode. Thus purified, the nanoparticles may be collected either as a solid or redispersed in a good nonpolar solvent, such as chloroform, hexane, or toluene. A real-time video demonstration, showing both the collection and redissolution of CdTe nanoparticles in less than two minutes, is available in the Supporting Information. Figure 2 shows the absorption and emission of electropurified CdTe nanoparticles as compared to those before purification and those conventionally purified by repeated precipitation–dissolution. The essentially identical first exciton and emission peak positions and spectral broadening indicate that there are no significant variations between the electropurified nanoparticles and those purified by conventional precipitation–dissolution. The H NMR spectrum of these electropurified nanoparticles (Figure 3) reveals a clean product. Broad resonances consistent with bound oleic acid are observed at d= 1.1, 1.44, and 2.3, and 5.56 ppm. There is a notable absence of resonances attributable to the cadmium [*] Dr. J. D. Bass, Dr. X. Ai, Dr. P. M. Rice, Dr. T. Topuria, Dr. J. C. Scott, Dr. H.-C. Kim, Dr. Q. Song, Dr. R. D. Miller IBM Almaden Research Center 650 Harry Road, San Jose, CA 95120 (USA) Fax: (+1)408-927-2073 E-mail: jbass@us.ibm.com qsong@us.ibm.com

Significant Formation of Adipic Acid by Direct Oxidation of Cyclohexane Using Supported Nano‐Gold Catalysts

Adipic acid (AA) is one of the highest volume chemicals in world use with a wide range of commercial applications. This paper demonstrates the possibility of producing significant proportions of AA by the selective oxidation of cyclohexane (CH) in one step using various supported gold‐nanoparticle (AuNP) catalysts. The catalysts were characterized by ICP, BET, XRD, X‐ray photoelectron microscopy, and TEM. The catalytic activity tests were carried out in the liquid phase using autoclaves in the temperature range of 100–170 °C at 10 bar. A CH conversion of over 25 %, with 26% selectivity of AA and 70% selectivity of KA oil (cyclohexanone+cyclohexanol), was achieved over a nano‐gold/TiO2 (anatase) catalyst. The superior performance of this catalyst is attributed to the smaller size of AuNPs, which has an average particle size of 2 nm. Good correlation between activity and Au particle size could be achieved. Overall, the particle size of the AuNPs showed a strong influence on catalytic performance.

Microwave-assisted synthesis of monodispersed CdTe nanocrystals

High quality and monodispersed CdTe nanocrystals with tunable emission spectra ranging from 516 nm to 650 nm were synthesized by a highly reproducible microwave method.

Laser-induced photocatalytic inactivation of coliform bacteria from water using pd-loaded nano-WO3

Abstract Nano palladium-loaded on nano tungsten trioxide ( n -Pd/ n -WO 3 ), with 10% wt Pd loading, was prepared by the impregnation evaporation method. The n -WO 3 support was prepared by dehydration of tungstic acid (H 2 WO 4 ). The n -Pd/ n -WO 3 was characterized by Raman spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). This material was tested as a photocatalyst for inactivation and killing of coliform bacteria, by applying 355-nm pulsed UV laser radiations, generated from the third harmonic of Nd:YAG laser, to a model water sample, prepared using bacteria strains of Escherichia coli . The killing effect of n -Pd/ n - WO 3 on coliform bacteria was characterized by means of selective culture media. The photocatalysis process did result in a very high irreversible injury (99%) under investigated conditions. This process is cost-effective because no bacteria re-growth was recorded under optimum environment conditions. The disinfection rate of water was estimated by exponential decay. The conventional titania (TiO 2 ) semiconductor and commercially available WO 3 display a lower decay rate than that for n -Pd/ n -WO 3 .

A study of laser-induced blue emission with nanosecond decay of silicon nanoparticles synthesized by a chemical etching method

Silicon nanoparticles (Si NPs), exhibiting a strong visible photoluminescence (PL), have found many applications in optoelectronics devices, biomedical tags and flash memories. Chemical etching is a well-known method for synthesizing orange-luminescent, hydride-capped silicon nanoparticles (H/Si NPs). However, a blueshift in emission wavelength occurs when reducing the particle size to exciton Bohr radius or less. In this paper, we attempted to synthesize and characterize H/Si NPs that emit lower wavelengths at room temperature. We proved that our method succeeded in synthesizing H/Si NPs with emission in the blue region. The wavelength-resolved and time-resolved studies of the PL were executed for H/Si NPs in methanol (MeOH), pyridine (py) and furan, using the 355 nm pulsed radiation from a Nd:YAG laser. In addition, excitation wavelength-dependent and PL studies were executed using the spectrofluorometer with a xenon (Xe) broad band light source. We noticed solvent-dependent PL spectra with sharp peaks near 420 nm and a short lifetime less than 100 ns. The morphology and particle size were investigated by high resolution transmission electron microscope (HRTEM). Particles as small as one nanometer were observed in MeOH and py suspensions while two-nanometer particles were observed in the furan suspension.

Cyclo­hexyl­ammonium nitrate

In the title salt, C6H14N+·NO3 −, the cyclohexyl ring adopts a chair conformation. The ammonium group occupies an equatorial position and the crystal struture is stabilized by intermolecular N—H⋯O hydrogen-bonding interactions, resulting in a three-dimensional network.