This article reviews the basic principles of and recent developments in electrochromic, photochromic, and thermochromic materials for applications in smart windows. Compared with current static windows, smart windows can dynamically modulate the transmittance of solar irradiation based on weather conditions and personal preferences, thus simultaneously improving building energy efficiency and indoor human comfort. Although some smart windows are commercially available, their widespread implementation has not yet been realized. Recent advances in nanostructured materials provide new opportunities for next-generation smart window technology owing to their unique structure-property relations. Nanomaterials can provide enhanced coloration efficiency, faster switching kinetics, and longer lifetime. In addition, their compatibility with solution processing enables low-cost and high-throughput fabrication. This review also discusses the importance of dual-band modulation of visible and near-infrared (NIR) light, as nearly 50% of solar energy lies in the NIR region. Some latest results show that solution-processable nanostructured systems can selectively modulate the NIR light without affecting the visible transmittance, thus reducing energy consumption by air conditioning, heating, and artificial lighting.
Ion exchange membranes are used in various membrane-based processes (e.g., electrodialysis, fuel cells). Charged solute transport is largely governed by the charged groups on the polymer backbone. In this review, fundamental relationships describing salt permeability and ionic conductivity, as well as water permeability, in charged polymers are developed within the framework of the Nernst-Planck and solution-diffusion models. The influence of fixed charge groups and polymer structure on water sorption and diffusion is discussed. Current understanding of ion partitioning in charged polymers, focusing on the use of thermodynamic models (i.e., Donnan theory) to describe such phenomena, is summarized. Ion diffusivity data from the literature are interpreted using a model developed by Mackie and Meares to assess relative and absolute effects of the polymer and fixed charge groups on ion diffusivity. Furthermore, membrane requirements for several important technologies are listed. Knowledge gaps and opportunities for fundamental research are also discussed.
Establishing an explicit feedback connection between production management and process control decisions is a key requirement for more nimble and cost effective process operations in today’s variable market conditions. Past research efforts focused on embedding dynamic process information in the production scheduling problem. In this article, we propose a novel framework for closing the scheduling loop, based on considering the process-level events and disturbances that impact the implementation of scheduling decisions. We emphasize the role of a comprehensive fault detection, isolation and reconstruction mechanism as a trigger for rescheduling decisions and for reflecting the process capabilities altered by these events in the rescheduling problem formulation. Our framework is agnostic to the process type, and we present two (continuous process, sequential batch process) case studies to demonstrate its applicability.
Student Award for Outstanding Research Winner in the Ph.D. Category for the 2017 Society for Biomaterials Annual meeting and Exposition, April 5-8, 2017, Minneapolis, Minnesota: Characterization of protein interactions with molecularly imprinted hydrogels that possess engineered affinity for high isoelectric point biomarkersby Clegg, JR; Zhong, JX; Irani, AS; Gu, J; Spencer, DS; Peppas, NA
Molecularly imprinted polymers (MIPs) with selective affinity for protein biomarkers could find extensive utility as environmentally robust, cost-efficient biomaterials for diagnostic and therapeutic applications. In order to develop recognitive, synthetic biomaterials for prohibitively expensive protein biomarkers, we have developed a molecular imprinting technique that utilizes structurally similar, analogue proteins. Hydrogel microparticles synthesized by molecular imprinting with trypsin, lysozyme, and cytochrome c possessed an increased affinity for alternate high isoelectric point biomarkers both in isolation and plasma-mimicking adsorption conditions. Imprinted and non-imprinted P(MAA-co-AAm-co-DEAEMA) microgels containing PMAO-PEGMA functionalized polycaprolactone nanoparticles were net-anionic, polydisperse, and irregularly shaped. MIPs and control non-imprinted polymers (NIPs) exhibited regions of Freundlich and BET isotherm adsorption behavior in a range of non-competitive protein solutions, where MIPs exhibited enhanced adsorption capacity in the Freundlich isotherm regions. In a competitive condition, imprinting with analogue templates (trypsin, lysozyme) increased the adsorption capacity of microgels for cytochrome c by 162% and 219%, respectively, as compared to a 122% increase provided by traditional bulk imprinting with cytochrome c. Our results suggest that molecular imprinting with analogue protein templates is a viable synthetic strategy for enhancing hydrogel-biomarker affinity and promoting specific protein adsorption behavior in biological fluids.
Understanding the effect of partial N3–to-O2- substitution and H+-to-K+ exchange on photocatalytic water reduction activity of Ruddlesden-Popper layered perovskite KLaTiO4by Kawashima, K; Hojamberdiev, M; Chen, SS; Yubuta, K; Wagata, H; Domen, K; Teshima, K
Ruddlesden-Popper perovskites, HLaTiO4 and HLaTiO4-xNx were prepared by proton exchange of layered KLaTiO4 synthesized by a solid-state reaction and KLaTiO4-xNx obtained by nitridation, respectively. The influence of nitridation time on crystal structure, morphology, and absorption wavelength and optical band-gap energy of KLaTiO4 crystals was studied. According to the XRD and SEM results, the crystal structure and plate-like morphology of the parent oxide were roughly retained even after nitridation at 800 degrees C for 10 h. The absorption edge wavelength of the KLaTiO4 crystals was found to be at about 350 nm (E-g = 3.54 eV), while the absorption edge wavelength of the KLaTiO4-xNx crystals (after 10 h nitridation) was about 586 nm (E-g = 2.12 eV). To investigate the effect of partial N3–to-O(2-)substitution and H+-to-K+ exchange on photocatalytic water reduction activity of Ruddlesden-Popper layered perovskite KLaTiO4, the photocatalytic activity for water reduction half-reaction over Pt-photodeposited KLaTiO4, KLaTiO4-xNx, HLaTiO4, and HLaTiO4-xNx was evaluated under simulated solar light. Among all the samples, Pt-photodeposited KLaTiO4 exhibited the highest photocatalytic activity for H-2 evolution. In contrast, Pt-photodeposited KLaTiO4-xNx showed a low photostability and photocatalytic activity for H-2 evolution due to the negative impact of the defective layer and reduced titanium species. In addition, perovskite oxynitride [LaTiO4-xNx](-)nanosheets were successfully fabricated by a mechanical exfoliation (sonication) of the KLaTiO4-xNx crystals. The colloidal suspension of the oxynitride nanosheets showed a Tyndall effect, implying their good dispersion and stability in water
In a recent paper [C. E. Bertrand et al., J. Chem. Phys. 145, 014502 (2016)], we have shown that the collective dynamics of methanol shows a fast relaxation process related to the standard density-fluctuation heat mode and a slow non-Fickian mode originating from the hydrogen bonded molecular associates. Here we report on the length scale dependence of this slow relaxation process. Using quasielastic neutron scattering and molecular dynamics simulations, we show that the dynamics of the slow process is affected by the structuring of the associates, which is accessible through polarized neutron diffraction experiments. Using a series of partially deuterated samples, the dynamics of the associates is investigated and is found to have a similar time scale to the lifetime of hydrogen bonding in the system. Both the structural relaxation and the dynamics of the associates are thermally activated by the breaking of hydrogen bonding.
Colloidal silica nanoparticles with average diameters less than 100 nm were made using a modified Stober method involving tetraethylorthosilicate (TEOS) and octadecyl trimethoxysilane (OTMOS) as a surface modifier. We show that the hydrophobicity of the nanoparticles could be tuned in this one-step reaction by introducing methanol as a co-solvent with ethanol and optimizing the ammonium hydroxide concentration and time elapsed between TEOS and OTMOS addition. Using this approach, silica nanoparticles could be made directly with the proper surface hydrophobicity to stabilize invert (water-in-oil) emulsions with shear-thinning rheological behavior as needed in oil drilling applications. Particle characterization data from transmission and scanning electron microscopy (TEM and SEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), and contact angle measurements are presented.
Ring-Opening Polymerization of Epoxides: Facile Pathway to Functional Polyethers via a Versatile Organoaluminum Initiatorby Rodriguez, CG; Ferrier, RC; Helenic, A: Lynd, NA
We report a new class of organoaluminum-based initiator for anionic ring-opening polymerization of epoxides that is simple to synthesize from readily available precursors. The resultant organometallic initiator was the triethylaluminum adduct of (2-dibenzylamino)ethoxy-diethylaluminum (TAxEDA) [(AlEt3)center dot(O(AlEt2) CH2CH2N(Bn)(2))], which was isolated by direct crystallization from the reaction medium and then compositionally and structurally characterized by NMR spectroscopy and XRD. We studied the reactivity and versatility of the new initiator through the polymerization of propylene oxide, butylene oxide, epichlorohydrin, and allyl glycidyl ether into homopolymer, statistical copolymer, and block copolymer architectures with heterobifunctional end-groups consisting of dibenzylamine and hydroxyl functionalities. The TAxEDA-initiated polymerizations were consistent with a controlled, living, anionic mechanism that was tolerant of chemical functionality and exhibited no chain transfer to monomer that limits the traditional anionic ring-opening polymerization of substituted epoxides.
Improved activation of adsorbed O-2 by co-adsorbed H2O on the Pd-Au(111) surface has been observed. When co-adsorbed with H2O, O-2 admolecules on the Pd-Au surface are more strongly bound via their interactions with H2O. This interaction leads to large enhancements in the dissociation of O-2 as determined via the generation of CO2 upon exposure to CO.
Control of Primary Particle Spacing in Gold Nanoparticle Clusters for Both High NIR Extinction and Full Reversibilityby Moaseri, E; Stover, RJ; Changalvaie, B; Cepeda, AJ; Truskett, TM; Sokolov, KV; Johnston, KP
Reversible NIR-active nanoparticle clusters with controlled size from 20 to 100 nm were assembled from 5 nm gold nanoparticles (Au NP), with either citrate (CIT) or various binary ligands on the surface, by tuning the electrostatic repulsion and the hydrogen bonding via pH. The nanoclusters were bound together by vdW forces between the cores and the hydrogen bonds between the surface ligands and dissociated to primary nanoparticles over a period of 20 days at pH 5 and at pH 7. When high levels of citrate ligands were used on the primary particle surfaces, the large particle spacings in the nanoclusters led to only modest NIR extinction. However, a NIR extinction (E-1000/525) ratio of up to similar to 0.4 was obtained for nanoclusters with binary ligand mixtures composed of citrate and either cysteine (CYS), glutathione (GSH), or thioctic acid zwitterion (TAZ) while maintaining full reversibility to primary particles. The optimum ligand ratio for both an E-1000/525 of similar to 0.4 and full reversibility decreased with increasing length of the secondary ligand (1.5/1 for CYS/CIT, 0.75/1 for GSH/CIT, and 0.5/1 for TAZ/CIT) because a longer secondary ligand maintains a sufficient interparticle spacing required for dissociation more effectively. Interestingly, the zeta potential and the first-order rate constant for nanocluster dissociation were similar for all three systems at the optimum ligand ratios. After incubation in 10 mM GSH solution (intracellular concentration), only the TAZ/CIT primary nanoparticles were resistant to protein opsonization in 100% fetal bovine serum, as the bidentate binding and zwitterion tips of TAZ resisted GSH exchange and protein opsonization, respectively.