Time filter

Source Type

Luijten E.,Northwestern University | Granick S.,Stanford University | Granick S.,Urbana University | Granick S.,Center for Soft and Living Matter
Annual Review of Physical Chemistry | Year: 2015

Burgeoning interest in supracolloidal assembly has reached the point at which the field can seek so-called intelligent design rather than solely rely on evolution. Emphasizing Janus and triblock particles, this review presents a progress report on formulating design rules for the assembly of interesting structures. We discuss how to design building blocks, bearing in mind that patchy particles embody not just geometric shape but also chemical shape, that chemical shape determines particle-particle interactions, and that the assembly process can be designed to proceed in hierarchical stages. Remarks are included about the potential of kinetic and nonequilibrium control, as well as the potential for the augmented use of soft building blocks. Whereas the reverse design problem, in which arbitrarily selected structures can be designed from the bottom up, still stands as a grand challenge, the field has reached the point of understanding necessary, although not always sufficient, conditions. © 2015 by Annual Reviews. All rights reserved.

Kim S.H.,University of Illinois at Urbana - Champaign | Madak-Erdogan Z.,University of Illinois at Urbana - Champaign | Bae S.C.,Center for Soft and Living Matter | Carlson K.E.,University of Illinois at Urbana - Champaign | And 4 more authors.
Journal of the American Chemical Society | Year: 2015

Estrogen conjugates with a polyamidoamine (PAMAM) dendrimer have shown remarkably selective regulation of the nongenomic actions of estrogens in target cells. In response to pH changes, however, these estrogen-dendrimer conjugates (EDCs) display a major morphological transition that alters the accessibility of the estrogen ligands that compromises the bioactivity of the EDC. A sharp break in dynamic behavior near pH 7 occurs for three different ligands on the surface of a PAMAM-G6 dendrimer: a fluorophore (tetramethylrhodamine [TMR]) and two estrogens (17α-ethynylestradiol and diphenolic acid). Collisional quenching and time-resolved fluorescence anisotropy experiments with TMR-PAMAM revealed high ligand shielding above pH 7 and low shielding below pH 7. Furthermore, when the pH was cycled from 8.5 (conditions of ligand-PAMAM conjugation) to 4.5 (e.g., endosome/lysosome) and through 6.5 (e.g., hypoxic environment) back to pH 8.5, the 17α-ethynylestradiol- and diphenolic acid-PAMAM conjugates experienced a dramatic, irreversible loss in cell stimulatory activity; dynamic NMR studies indicated that the hormonal ligands had become occluded within the more hydrophobic core of the PAMAM dendrimer. Thus, the active state of these estrogen-dendrimer conjugates appears to be metastable. This pH-dependent irreversible masking of activity is of considerable relevance to the design of drug conjugates with amine-bearing PAMAM dendrimers. © 2015 American Chemical Society.

News Article | March 18, 2016
Site: phys.org

Prof. Oh-Hoon Kwon (School of Natural Science) is posing for a portrait with the ultrafast laser spectroscopy in the background. Credit: UNIST A new research, affiliated with UNIST has been featured as a 'Hot Article' on the front cover of the March issue of Chemistry: A European Journal. This study has been regarded as "very important" because it offers a new framework for understanding reactions in organic chemistry. The team, made up of five Korean scientists and experts from the IBS Center for Soft and Living Matter, the Korea Advanced Institute of Science and Technology (KAIST), and Ulsan National Institute of Science and Technology (UNIST), reported the basicity enhancement of an alcohol by hydrogen-bonded clustering. In their study, the team addressed the cooperative role of alcohols, the simplest organic protic compounds, in one of elementary reactions in chemistry, the acid-base reaction, in a quantitative manner. According to Prof. Oh-Hoon Kwon (Department of Chemistry, UNIST), the corresponding author of this study, "The motivation of this work, in particular, was the observation that the photoinduced proton transfer can also occur in alcohol with a properly chosen photoacid." The formation of an alkyl oxonium ion has long been proposed as a key reaction intermediate in alcohol dehydration. This was examined by time-resolved fluorescence quenching of a strong photoacid in their study. Through their analysis, the research team revealed, for the first time, that the collaboration of two alcohol molecules through hydrogen bonding is critical to enhancing their reactivity and promotes the resulting alcohol cluster to form an effective Brønsted base when reacting with an acid as strong as sulfuric acid. Prof. Kwon states, "This finding addresses, as in water, the cooperative role of protic solvent molecules to facilitate nonaqueous acid-base reactions." He continues, "However, further systematic investigation on the size variation of clusters formed from diverse alcohols of different basicity and photoacids of different acidity is currently underway." Explore further: Researchers move one step closer to sustainable hydrogen production More information: Sun-Young Park, Young Min Lee, Kijeong Kwac, Yousung Jung, Oh-Hoon Kwon. "Alcohol Dimer is Requisite to Form an Alkyl Oxonium Ion in the Proton Transfer of a Strong (Photo) Acid to Alcohol". Chemistry: A European Journal. (2016)

Grzybowski B.A.,Center for Soft and Living Matter | Huck W.T.S.,Radboud University Nijmegen
Nature Nanotechnology | Year: 2016

For some decades now, nanotechnology has been touted as the 'next big thing' with potential impact comparable to the steam, electricity or Internet revolutions-but has it lived up to these expectations? While advances in top-down nanolithography, now reaching 10-nm resolution, have resulted in devices that are rapidly approaching mass production, attempts to produce nanoscale devices using bottom-up approaches have met with only limited success. We have been inundated with nanoparticles of almost any shape, material and composition, but their societal impact has been far from revolutionary, with growing concerns over their toxicity. Despite nebulous hopes that making hierarchical nanomaterials will lead to new, emergent properties, no breakthrough applications seem imminent. In this Perspective, we argue that the time is ripe to look beyond individual nano-objects and their static assemblies, and instead focus on systems comprising different types of 'nanoparts' interacting and/or communicating with one another to perform desired functions. Such systems are interesting for a variety of reasons: they can act autonomously without external electrical or optical connections, can be dynamic and reconfigurable, and can act as 'nanomachines' by directing the flow of mass, energy or information. In thinking how this systems nanoscience approach could be implemented to design useful-as opposed to toy-model-nanosystems, our choice of applications and our nanoengineering should be inspired by living matter.

Mahato P.,Kyushu University | Yanai N.,Kyushu University | Yanai N.,Japan Science and Technology Agency | Sindoro M.,Urbana University | And 3 more authors.
Journal of the American Chemical Society | Year: 2016

Photon upconversion (UC) based on triplet-triplet annihilation (TTA) has the potential to enhance significantly photovoltaic and photocatalytic efficiencies by harnessing sub-bandgap photons, but the progress of this field is held back by the chemistry problem of how to preorganize multiple chromophores for efficient UC under weak solar irradiance. Recently, the first maximization of UC quantum yield at solar irradiance was achieved using fast triplet energy migration (TEM) in metal-organic frameworks (MOFs) with ordered acceptor arrays, but at the same time, a trade-off between fast TEM and high fluorescence efficiency was also found. Here, we provide a solution for this trade-off issue by developing a new strategy, triplet energy migration, annihilation and upconverted singlet energy collection (TEM-UPCON). The porous structure of acceptor-based MOF crystals allows triplet donor molecules to be accommodated without aggregation. The surface of donor-doped MOF nanocrystals is modified with highly fluorescent energy collectors through coordination bond formation. Thanks to the higher fluorescence quantum yield of surface-bound collectors than parent MOFs, the implementation of the energy collector greatly improves the total UC quantum yield. The UC quantum yield maximization behavior at ultralow excitation intensity was retained because the TTA events take place only in the MOF acceptors. The TEM-UPCON concept may be generalized to collectors with various functions and would lead to quantitative harvesting of upconverted energy, which is difficult to achieve in common molecular diffusion-based systems. © 2016 American Chemical Society.

Lach Sl.,Center for Soft and Living Matter | Yoon S.M.,Center for Soft and Living Matter | Grzybowski B.A.,Center for Soft and Living Matter
Chemical Society Reviews | Year: 2016

Under non-equilibrium conditions, liquid droplets coupled to their environment by sustained flows of matter and/or energy can become active systems capable of various life-like functions. When fueled by even simple chemical reactions, such droplets can become tactic and can perform "intelligent" tasks such as maze solving. With more complex chemistries, droplets can support basic forms of metabolism, grow, self-replicate, and exhibit evolutionary changes akin to biological cells. There are also first exciting examples of active droplets connected into larger, tissue-like systems supporting droplet-to-droplet communication, and giving rise to collective material properties. As practical applications of droplets also begin to appear (e.g., in single-cell diagnostics, new methods of electricity generation, optofluidics, or sensors), it appears timely to review and systematize progress in this highly interdisciplinary area of chemical research, and also think about the avenues (and the roadblocks) for future work. © 2016 The Royal Society of Chemistry.

Emami F.S.,Northwestern University | Vahid A.,Northwestern University | Wylie E.K.,Northwestern University | Szymkuc S.,Polish Academy of Sciences | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2015

A thermodynamically guided calculation of free energies of substrate and product molecules allows for the estimation of the yields of organic reactions. The non-ideality of the system and the solvent effects are taken into account through the activity coefficients calculated at the molecular level by perturbed-chain statistical associating fluid theory (PC-SAFT). The model is iteratively trained using a diverse set of reactions with yields that have been reported previously. This trained model can then estimate a priori the yields of reactions not included in the training set with an accuracy of ca. ±15 %. This ability has the potential to translate into significant economic savings through the selection and then execution of only those reactions that can proceed in good yields. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen K.,Urbana University | Wang B.,Urbana University | Wang B.,Stanford University | Granick S.,Urbana University | Granick S.,Center for Soft and Living Matter
Nature Materials | Year: 2015

In contrast to Brownian transport, the active motility of microbes, cells, animals and even humans often follows another random process known as truncated Lévy walk. These stochastic motions are characterized by clustered small steps and intermittent longer jumps that often extend towards the size of the entire system. As there are repeated suggestions, although disagreement, that Lévy walks have functional advantages over Brownian motion in random searching and transport kinetics, their intentional engineering into active materials could be useful. Here, we show experimentally in the classic active matter system of intracellular trafficking that Brownian-like steps self-organize into truncated Lévy walks through an apparent time-independent positive feedback such that directional persistence increases with the distance travelled persistently. A molecular model that allows the maximum output of the active propelling forces to fluctuate slowly fits the experiments quantitatively. Our findings offer design principles for programming efficient transport in active materials. © 2015 Macmillan Publishers Limited. All rights reserved.

PubMed | Urbana University, Northwestern University and Center for Soft and Living Matter
Type: Journal Article | Journal: Nature materials | Year: 2016

Active materials represent a new class of condensed matter in which motile elements may collectively form dynamic, global structures out of equilibrium. Here, we present a general strategy to reconfigure active particles into various collective states by introducing imbalanced interactions. We demonstrate the concept with computer simulations of self-propelled colloidal spheres, and experimentally validate it in a two-dimensional (2D) system of metal-dielectric Janus colloids subjected to perpendicular a.c. electric fields. The mismatched, frequency-dependent dielectric responses of the two hemispheres of the colloids allow simultaneous control of particle motility and colloidal interactions. We realized swarms, chains, clusters and isotropic gases from the same precursor particle by changing the electric-field frequency. Large-scale polar waves, vortices and jammed domains are also observed, with the persistent time-dependent evolution of their collective structure evoking that of classical materials. This strategy of asymmetry-driven active self-organization should generalize rationally to other active 2D and three-dimensional (3D) materials.

PubMed | Urbana University and Center for Soft and Living Matter
Type: | Journal: Nature communications | Year: 2016

Super-resolution stimulated emission depletion (STED) microscopy is adapted here for materials characterization that would not otherwise be possible. With the example of organic light-emitting diodes (OLEDs), spectral imaging with pixel-by-pixel wavelength discrimination allows us to resolve local-chain environment encoded in the spectral response of the semiconducting polymer, and correlate chain packing with local electroluminescence by using externally applied current as the excitation source. We observe nanoscopic defects that would be unresolvable by traditional microscopy. They are revealed in electroluminescence maps in operating OLEDs with 50nm spatial resolution. We find that brightest emission comes from regions with more densely packed chains. Conventional microscopy of an operating OLED would lack the resolution needed to discriminate these features, while traditional methods to resolve nanoscale features generally cannot be performed when the device is operating. This points the way towards real-time analysis of materials design principles in devices as they actually operate.

Loading Center for Soft and Living Matter collaborators
Loading Center for Soft and Living Matter collaborators