1. INTRODUCTION Among the classes of highly porous materials, metalÀorganic frameworks (MOFs) are unparalleled in their degree of tunability and structural diversity as well as their range of chemical and physical properties. MOFs are extended crystalline structures wherein metal cations or clusters of cations (\" nodes \") are connected by multitopic organic \" strut \" or \" linker \" ions or molecules. The variety of metal ions, organic linkers, and structural motifs affords an essentially infinite number of possible combinations. 1 Furthermore, the possibility for postsynthetic modification adds an additional dimension to the synthetic variability. 2 Coupled with the growing library of experimentally determined structures, the potential to computationally predict, with good accuracy, affinities of guests for host frameworks points to the prospect of routinely predesigning frameworks to deliver desired properties. 3,4 MOFs are often compared to zeolites for their large internal surface areas, extensive porosity, and high degree of crystallinity. Correspondingly, MOFs and zeolites have been utilized for many of the same applications

Metal–Organic Framework Materials as Chemical Sensors

▪ Abstract Photoexcitation of a semiconductor with photons above the semiconductor band gap creates electrons and holes that are out of equilibrium. The rates at which the photogenerated charge carriers return to equilibrium via thermalization through carrier scattering, cooling by phonon emission, and radiative and nonradiative recombination are important issues. The relaxation processes can be greatly affected by quantization effects that arise when the carriers are confined to regions of space that are small compared with their deBroglie wavelength or the Bohr radius of bulk excitons. The effects of size quantization in semiconductor quantum wells (carrier confinement in one dimension) and quantum dots (carrier confinement in three dimensions) on the respective carrier relaxation processes are reviewed, with emphasis on electron cooling dynamics. The implications of these effects for applications involving radiant energy conversion are also discussed.

Spectroscopy and hot electron relaxation dynamics in semiconductor quantum wells and quantum dots.

Sustainable technologies applied to energy-related applications should develop a pivotal role in the next decades. In particular, carbon dioxide capture from flue gases emitted by fossil-fueled power plants should play a pivotal role in controlling and reducing the greenhouse effect. Therefore, the development of new materials for carbon capture purposes has merged as central research line, for which many alternatives have been proposed. Ionic liquids (ILs) have emerged as one of the most promising choices for carbon capture, but in spite of their promising properties, some serious drawbacks have also appeared. Deep eutectic solvents (DESs) have recently been considered as alternatives to ILs that maintain most of their relevant properties, such as task-specific character, and at the same time avoid some of their problems, mainly from economic and environmental viewpoints. DES production from low-cost and natural sources, together with their almost null toxicity and total biodegradability, makes these sol...

Deep Eutectic Solvents: Physicochemical Properties and Gas Separation Applications

Microwave-assisted preparation of inorganic nanostructures in liquid phase.

ConspectusThe magic of microwave (MW) heating technique, termed the Bunsen burner of the 21st century, has emerged as a valuable alternative in the synthesis of organic compounds, polymers, inorganic materials, and nanomaterials. Important innovations in MW-assisted chemistry now enable chemists to prepare catalytic materials or nanomaterials and desired organic molecules, selectively, in almost quantitative yields and with greater precision than using conventional heating. By controlling the specific MW parameters (temperature, pressure, and ramping of temperature) and choice of solvents, researchers can now move into the next generation of advanced nanomaterial design and development.Microwave-assisted chemical reactions are now well-established practices in the laboratory setting although some controversy lingers as to how MW irradiation is able to enhance or influence the outcome of chemical reactions. Much of the discussion has focused on whether the observed effects can, in all instances, be rationa...

Microwave-Assisted Chemistry: Synthetic Applications for Rapid Assembly of Nanomaterials and Organics

We report the direct deposition of strained InGaAs‐dot structures with a diameter of about 15 nm on GaAs surfaces by metalorganic chemical vapor deposition growth. High resolution scanning electron micrographs show highly uniform quantum‐sized dots formed by the Stranski–Krastanow growth mode. The sharp photoluminescence emission band of buried dot structures indicates efficient carrier capture and a homogeneous heterointerface. The average dot size and area dot density can be controlled accurately by growth temperature, and InGaAs deposition thickness, respectively.

Highly uniform InGaAs/GaAs quantum dots (∼15 nm) by metalorganic chemical vapor deposition

Self‐alignment of InGaAs quantum dots was achieved by growing the quantum dots on the multiatomic steps in metalorganic chemical vapor deposition. In this technique, first GaAs epilayer with multiatomic step structures along straight lines was grown on a vicinal GaAs substrate under appropriate growth conditions. Then, the InGaAs quantum dots were grown selectively on the multiatomic step edges using strain effects. This growth technique results in spontaneously aligned InGaAs quantum dots without any preprocessing technique prior to the growth.

In situ fabrication of self‐aligned InGaAs quantum dots on GaAs multiatomic steps by metalorganic chemical vapor deposition

Successful fabrication of thin GaAs quantum wires (120–200 A)×(200–300 A) by a novel metal‐organic chemical‐vapor‐deposition growth technique is reported. The GaAs quantum wires were grown on a V groove formed by two GaAs triangular prisms which were selectively grown on SiO2 masked substrates. The V groove has a very sharp corner at the bottom, which results in reduction of the effective width of the quantum wire structures. The measurement of photoluminescence and photoluminescence excitation spectra with polarization dependence indicate the existence of the quantized state in the quantum wires.

Fabrication of GaAs quantum wires on epitaxially grown V grooves by metal‐organic chemical‐vapor deposition

Three different zeolites, which are zeolite A, silicalite-1 and sodalite, were deposited on quartz crystal microbalance (QCM) oscillators with fundamental resonance frequency of 4.7 MHz. Three QCMs, as well as one without zeolites as a reference, were exposed to single gases such as NO, SO 2 and H 2 O in He at 443 K. The frequency shifts and their differential values to time were measured, and both of them are tested to elucidate which is more useful to quanlify and quatify these single gases using principal component analysis (PCA). Based on these results, mixed gases of NO and SO 2 in several compositions in He are examined. Mixed-gas data are also qualified and quantified using PCA. These results suggest that the sensor system with the differential values which represent sorption-kinetics, instead of the frequency shifts representing sorption-equilibria, overcame the disadvantages of the conventional QCM sensors and showed favorable qualification and quantification performances for the gas mixture.

Gas sensing with zeolite-coated quartz crystal microbalances—principal component analysis approach

Continuous synthesis of silver nanoparticles based on a polyol process was conducted using a microwave-assisted flow reactor installed in a cylindrical resonance cavity Silver nitrate (AgNO3) and poly(N-vinylpyrrolidone) (PVP) dissolved in ethylene glycol were used respectively as a silver metal precursor and as a capping agent of nanoparticles Ethylene glycol worked as the solvent and simultaneously as the reductant Silver nanoparticles of narrow size distributions were synthesized steadily for 5 h, maintaining almost constant yield (>93%) and quality The reaction was achieved within 28 s of residence time, although nanoparticles were not formed under this flow rate by conventional heating A narrower particle size distribution was realized by the increased flow rate of the reaction solution Nanoparticles of 98 nm average size with a standard deviation of 09 nm were synthesized at the rate of 100 ml h−l

Masateru Nishioka

Papers

Highly uniform InGaAs/GaAs quantum dots (∼15 nm) by metalorganic chemical vapor deposition

In situ fabrication of self‐aligned InGaAs quantum dots on GaAs multiatomic steps by metalorganic chemical vapor deposition

Fabrication of GaAs quantum wires on epitaxially grown V grooves by metal‐organic chemical‐vapor deposition

Gas sensing with zeolite-coated quartz crystal microbalances—principal component analysis approach

Continuous synthesis of monodispersed silver nanoparticles using a homogeneous heating microwave reactor system.