Centimeter-scale mesoporous silica monoliths were synthesized by a multi-step fabrication process by combining cooperative and evaporation-induced self-assembly with high-pressure compaction. The fabricated monoliths were highly permeable with a surface area exceeding 270 m2/g from a continuous SBA-16 cubic mesoporous matrix. This new type of mesoporous solids exhibits excellent mechanical stability comparable to sedimentary rocks, despite having a low density of only ~ 1.1 g/cm3.

Nanoconfined water plays a pivotal role in a vast number of fields ranging from biological and materials sciences to catalysis, nanofluidics and geochemistry. Here, we report the freezing and melting behavior of water (D2O) nanoconfined in architected silica-based matrices including Vycor glass and mesoporous silica SBA-15 and SBA-16 with pore diameters ranging between 4–15 nm, which are investigated using differential scanning calorimetry and 2H nuclear magnetic resonance spectroscopy. The results provide compelling evidence that the extreme dynamical heterogeneity of water molecules is preserved over distances as small as a few angstroms. Solidification progresses in a layer-by-layer fashion with a coexistence of liquid-like and solid-like dynamical fraction at all temperatures during the transition process. The previously reported fragile-to-strong dynamic transition in nanoconfined water is argued to be a direct consequence of the layer-by-layer solidification.

Advancing a mechanistic understanding of the colloidal to solid-phase transformations of silica allows us to tune these meso-scale structures. In this study, we probe the structural transformations associated with the formation of mesoporous silica particles, SBA-15 using in-operando Small Angle X-ray Scattering (SAXS) and Grazing Incidence-Small Angle X-ray Scattering (GI-SAXS). The chemical transformations associated with the hydrolysis and condensation of silica particles is investigated using Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR) measurements. Fast polymerization of Si-O-Si species to form mesoporous silica is noted when SBA-15 is synthesized in the presence of nitrate salts, due to the “salting-in” effect or enhanced solubility of polymers. However, aging the silica particles resulted in plate-like morphologies in the absence of the nitrate salt and spherical morphologies in the presence of nitrate salt. Early onset of nucleation of silica particles in the presence of nitrate salts was captured using GI-SAXS measurements. These studies show that the rational basis for developing new synthesis routes for accelerated kinetics or specific meso-scale structures can be informed by detailed characterization of the evolution in chemistry and meso-scale structure of these materials.

To determine a general correlation between structure and dynamic magnetic properties of porous materials, the frequencies of magnetic spin waves are studied by Brillouin light scattering from nickel inverse opals and backed up by micromagnetic simulations. Within the observed unit cell size regime between 400 and 800 nm, discrete thickness standing modes are found to change with unit cell size. By applying pair correlation functions of the inverse opal solid phase normal to the applied field to an equation for perpendicular standing modes, the directional and unit cell size‐dependent spectral intensities above the surface mode region can be traced. Thus, an accessible general approach for the prediction of standing spin waves in porous materials is obtained.

Spatiotemporal heterogeneity is one of the hallmarks of the relaxation dynamics associated with the glass transition. A key question in this regard is whether the dynamical heterogeneity has a structural origin. We report differential scanning calorimetry (DSC) data that reveal the presence of extreme spatial heterogeneity in the freezing dynamics of water (D2O) and the glass transition dynamics in the supercooled molecular liquid ortho-terphenyl (OTP), when these liquids are confined in nano-architected mesoporous silica with interconnected pores of different geometry. The results demonstrate, for the first time, that despite connectivity between the pores, nanoconfined water and OTP display distinct freezing/melting points and glass transition temperatures characteristic of each pore type. Viewed as a whole, these experimental results point to the coexistence of strong spatial heterogeneities over length scales of a few nanometers in the structure and dynamics of these liquids, suggesting a close mechanistic connection between them.

CONSPECTUS: Core principles of chemistry are ubiquitously invoked to shed light on the nature of molecular level interactions in nanoconfined fluids, which play a pivotal role in a wide range of processes in geochemistry, biology, and engineering. A detailed understanding of the physicochemical processes involved in the flow, structural transitions, and freezing or melting behavior of fluids confined within nanometer-sized pores of solid materials is thus of enormous importance for both basic research and technological applications. This Account provides a perspective on new insights into the thermodynamic and kinetic transitions of nanoconfined fluids in their stable and metastable forms. After briefly introducing the unique properties of mesoporous silicas from the SBA, MCM, and FDU families that serve as the confinement matrices, combining highly ordered single and bimodal mesopore architectures with tunable pore sizes in the similar to 2-15 nm range and narrow size distributions, recent studies on melting/freezing behavior of water confined in these host matrices are reviewed. While differential scanning calorimetry (DSC) reveals a linear relationship between melting point depression and pore size (independent of the pore shape), as predicted by the Gibbs-Thomson relation, variable temperature H-2 wide-line nuclear magnetic resonance (NMR) spectroscopy studies confirm the core-shell model of water and give evidence for a layer-by-layer freezing mechanism, which gives rise to an apparent fragile-to-strong transition in the solidification dynamics. In contrast to the freezing/melting behavior of water, the effect of nanoconfinement on the glass transition of supercooled liquids is nonuniversal and the glass transition temperature T-g can either increase or decrease with the dimensionality and extent of confinement. This nonuniversal behavior is exemplified by the two glass-forming molecular liquids, glycerol and ortho-terphenyl (OTP). While glycerol shows an increase in T-g and a pronounced slowdown of the rotational dynamics of the constituent molecules due to a change in the molecular packing between the bulk and the confined liquid, OTP displays a linear and confining-mediadependent depression of T-g with increased confinement that is strongly influenced by the pore-liquid interface characteristics. This Account concludes with a focus on recent experimental evidence of extreme spatial and dynamical heterogeneity in both freezing and glass transition processes. This discovery was enabled by the unique mesoporous structures of SBA-16 and FDU-5, possessing bimodal architectures with two interconnected pore types of different size and shape (spherical and cylindrical). For the very first time, two melting points for water and two glass transitions for supercooled OTP, corresponding to a specific pore type, were observed. Collectively, these observations strongly suggest a close mechanistic connection between the local fluctuations in the structure and dynamics of nanoconfined liquids. While the findings reviewed in this Account provide new insights into thermodynamic and kinetic transitions of fluids, there remain many unanswered questions regarding the effects of nanoconfinement on the fundamental properties of fluids, which offer exciting future opportunities in chemical research.

The origin of the brilliant near angle-independent coloration of the weevil Eupholus chevrolati was investigated by a combination of optical and electron microscopy tools, photonic band structure calculations, and color mixing analysis. Optical microscopy and scanning micro-spectroscopy revealed the presence of micrometer-sized red, yellow, green, and blue reflective pixels covering the entire exoskeleton of the weevil. Scanning electron microscopy in combination with focused ion beam milling showed that each micro-pixel consisted of a diamond-based photonic crystal structure and the different reflective colors were the result of different orientations of the photonic crystal. Color mixing analysis was used to study the collective behavior of the reflective micro-pixels. A pointillist, additive color-mixing scheme of the reflective photonic crystal micro-pixels was determined as the origin of the weevil’s bright and near angle-independent yellow-green coloration.

The phase behavior change when fluids are in a confined system has been an important issue after shale reservoirs became the focus of new oil and gas resources. Most studies on phase behavior of confined fluid systems have focused on modeling pore size dependence upon critical properties with no direct experimental evidence. Direct bubble point measurements of hydrocarbon mixtures in two synthesized mesoporous materials are: provided in this work. Two different synthesized mesoporous silica materials, SBA-15 and SBA-16, having similar pore sites (namely, 4 nm), were used. Well-ordered nanopores with narrow pore size distribution characterized these synthesized mesoporous silica materials. Decane methane and octane methane mixtures in 90:10 molar ratios were employed. The phase diagrams of the hydrocarbon mixtures were generated using a commercial thermodynamic simulator. The bubble point pressure of bulk (no porous medium) mixtures of decane methane and octane methane and the bubble point pressures with mesoporous materials (SBA-15 and SBA-16) were measured experimentally. Experiments were also performed with micrometer-sized sand particles. The bubble point pressure results of the hydrocarbon mixtures in the mesoporous materials were lower than those in the bulk, while the bubble points with sand were closer to those with bulk measurements. The bubble point pressure with SBA-15 having the higher total porosity and inner porosity was slightly lower than that with SBA-16. The differences may also be attributed to the different pore morphologies in the two mesoporous materials.

Silica based crack-free monoliths having the same pore size range as the oil and gas producing north-american shales were synthesized using a new synthesis procedure. Crack-free monoliths were synthesized by controlling the evaporation rate. Evaporation rate of 0.4 g/cm(2) was found optimal for making monoliths in cylindrical enclosures of different sizes for experimentation. The focus of this work was to understand the effects of nano-sized porous media on the saturation pressures of a hydrocarbon mixture of methane and decane. The physicochemical properties of the synthesized monoliths were measured using X-ray diffraction (XRD), nitrogen adsorption/desorption isotherm (BET), pore size distribution curve, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of decane in saturated monoliths revealed different boiling points in comparison to pure decane. The experimentally measured saturation pressures at two different temperatures of the bulk hydrocarbon mixture (decane-methane) matched well with the simulated results. The bubble point pressures of a hydrocarbon mixture in the nano-sized monolith were lower (about 18%) than those in the bulk. (C) 2017 Elsevier Ltd. All rights reserved.

The unique properties of colloidal semiconductor nano crystals, or quantum dots, have attracted enormous interest in a wide range of applications, including energy, lighting, and biomedical fields. However, widespread implementation is hampered by the difficulty of developing large-scale and inexpensive synthesis routes, mainly due to our limited knowledge of formation reaction parameters. We report here a simple yet powerful method to experimentally determine critically important reaction parameters such as rate constants, activation barriers, equilibrium constants and reaction enthalpies. This method was applied to wurtzite cadmium: selenide nanocrystals, yielding activation energies for growth and dissolution of 14 +/- 6 kJ mol(-1) and 27 +/- 8 kJ mol(-1), respectively, and a reaction enthalpy for nanocrystal growth of -15 +/- 7 kJ mol(-1). Moreover, the Gibbs free energy for growth was found to be negative at low temperatures, whereas dissolution becomes the spontaneous process above 150 degrees C.

Spark plasma sintering (SPS) was used to compact chemically synthesized mesoporous silica powders with ordered hexagonal nanopore channels (~5 nm). Solid compact disks (~19 mm diameter) densified at processing temperatures from 600 to 1000 °C were characterized at multiple length scales using scanning electron microscopy, transmission electron microscopy, Vickers hardness tests, and Brunauer–Emmett–Teller gas adsorption measurements. Microscopy revealed both micro- and nanoporosity in the compacted disks and the hexagonal mesopore channels in the starting powders were retained during SPS at temperatures up to 850 °C under a uniaxial pressure of 10.6 MPa. The degree of macroporosity in SPS samples was correlated to the mechanical properties, surface area, and pore morphology. The macroporosity is retained up to 950 °C under the same pressure, and the degree of macroporosity increases when the mesopores collapse due to individual particle shrinkage. The results of multi-scale characterization of the mesoporous silica compacts were used to shed light on the role of nanostructure and microstructure on the mechanical and physical properties of SPS processed compacted disks.

A mix-and-match sol–gel deposition method allows fabrication of one-dimensional photonic bandgap materials with strategically placed porous layers.

The objective of this project was to develop and demonstrate a new class of tracers that offer great promise for use in characterizing fracture networks in EGS reservoirs. From laboratory synthesis and testing through numerical modeling and field demonstrations, we have demonstrated the amazing versatility and applicability of quantum dot tracers. This report summarizes the results of four years of research into the design, synthesis, and characterization of semiconductor nanocrystals (quantum dots) for use as geothermal tracers.

The artificial beetle is possibly the Holy Grail for practitioners of engineered biomimicry. An artificial beetle could gather and relay data and images from compromised environments on earth and other planets to decision makers. It could also be used for surveillance of foes and friends alike, and will require ethical foresight and oversight. What would it take to develop an artificial beetle? Several biotemplating techniques can be harnessed for the replication of external structural features of beetle bodies, and thus preserve functionalities such as coloration of the exoskeleton and the hydrophobicity of wings. The body cavity must host a power supply, motors to move the wings for flight, sensors to capture ambient conditions and images, and data transmitters and receivers to communicate with a remote command center. All of these devices must be very small and reliable.

A combination of optical absorption and scattering is used to detect tracer species in a strongly scattering medium. An optical setup was developed, consisting of a dual-beam scattering detection scheme in which sample scattering beam overlaps with the characteristic absorption feature of quantum dot tracer species, while the reference scattering beam is outside any absorption features of the tracer. This scheme was successfully tested in engineered breakthrough tests typical of wastewater and subsurface fluid analysis, as well as in batch analysis of oil and gas reservoir fluids and biological samples. Tracers were detected even under highly scattering conditions, conditions in which conventional absorption or fluorescence methods failed.

In fatigue, micrometer and sub-micrometer metal components do not have sufficient space to form persistent slip band (PSB) structures, which bring about the extrusions/intrusions with the size of a few micrometers in bulk metal. The characteristic feature of fatigue behavior at this scale is investigated using resonance vibration fatigue experiments on single crystal gold cantilevers of various sizes. Fatigue damage of extrusion/intrusion is formed on the cantilever surface in all specimens. The width of the extrusion/intrusion decreases with the size of cantilever, from hundreds to tens nanometers, which is much smaller than that in bulk components. And the slip traces formation is spatially periodic. The resolved shear stress to form an extrusion/intrusion is strongly dependent on the specimen size and is much higher than that in the bulk.