More detailed details on the dimensions of the dies, additional devices and videos of the running experiments are available in the supporting information.

The origin of the odd-even effect in properties of self-assembled monolayers (SAMs) and/or technologies derived from them is poorly understood. We report that hydrophobicity and, hence, surface wetting of SAMs are dominated by the nature of the substrate (surface roughness and identity) and SAM tilt angle, which influences surface dipoles/orientation of the terminal moiety. We measured static contact angles (θs) made by water droplets on n-alkanethiolate SAMs with an odd (SAM(O)) or even (SAM(E)) number of carbons (average θs range of 105.8-112.1°). When SAMs were fabricated on smooth "template-stripped" metal (M(TS)) surfaces [root-mean-square (rms) roughness = 0.36 ± 0.01 nm for Au(TS) and 0.60 ± 0.04 nm for Ag(TS)], the odd-even effect, characterized by a zigzag oscillation in values of θs, was observed. We, however, did not observe the same effect with rougher "as-deposited" (M(AD)) surfaces (rms roughness = 2.27 ± 0.16 nm for Au(AD) and 5.13 ± 0.22 nm for Ag(AD)). The odd-even effect in hydrophobicity inverts when the substrate changes from Au(TS) (higher θs for SAM(E) than SAM(O), with average Δθs |n - (n + 1)| ≈ 3°) to Ag(TS) (higher θs for SAM(O) than SAM(E), with average Δθs |n - (n + 1)| ≈ 2°). A comparison of hydrophobicity across Ag(TS) and Au(TS) showed a statistically significant difference (Student's t test) between SAM(E) (Δθs |Ag evens - Au evens| ≈ 5°; p < 0.01) but failed to show statistically significant differences on SAM(O) (Δθs |Ag odds - Au odds| ≈ 1°; p > 0.1). From these results, we deduce that the roughness of the metal substrate (from comparison of M(AD) versus M(TS)) and orientation of the terminal -CH2CH3 (by comparing SAM(E) and SAM(O) on Au(TS) versus Ag(TS)) play major roles in the hydrophobicity and, by extension, general wetting properties of n-alkanethiolate SAMs.

Paramagnetic ionic liquids (PILs) provide new capabilities to measurements of density using magnetic levitation (MagLev). In a typical measurement, a diamagnetic object of unknown density is placed in a container containing a PIL. The container is placed between two magnets (typically NdFeB, oriented with like poles facing). The density of the diamagnetic object can be determined by measuring its position in the magnetic field along the vertical axis (levitation height, h), either as an absolute value or relative to internal standards of known density. For density measurements by MagLev, PILs have three advantages over solutions of paramagnetic salts in aqueous or organic solutions: (i) negligible vapor pressures; (ii) low melting points; (iii) high thermal stabilities. In addition, the densities, magnetic susceptibilities, glass transition temperatures, thermal decomposition temperatures, viscosities, and hydrophobicities of PILs can be tuned over broad ranges by choosing the cation−anion pair. The low melting points and high thermal stabilities of PILs provide large liquidus windows for density measurements. This paper demonstrates applications and advantages of PILs in density-based analyses using MagLev.M agnetic levitation (MagLev) is a useful new method for measuring the density of a diamagnetic object. 1−9 MagLev, as developed in our laboratory, relies on paramagnetic solutions (typically generated by dissolving a paramagnetic salt, alone or as a chelate, in water or an organic solvent), placed in a magnetic field gradient, to suspend a diamagnetic object against gravity. 1 This procedure has broad generality but also six limitations: (i) Evaporation of the solvent from a solution of paramagnetic salt will increase the concentration of the paramagnetic species and, thus, the magnetic susceptibility of the solution. This evaporation of solvent complicates the use and storage of paramagnetic solutions and, in some applications, requires calibration or the use of internal standards. (ii) Aqueous solutions of paramagnetic salts cannot be used for density-based measurement of water-miscible or water-soluble analytes. (iii) Paramagnetic salts have high but ultimately finite solubility in water (the limiting solubility of MnCl 2 is ∼4.5 M) and even more limited solubility in organic solvents. Water has limited ability to dissolve the paramagnetic salts at subzero temperatures (<0°C). These limits to solubility constrain the range of densities that can be measured using these solutions. (iv) Some organic solvents used for watermiscible analytes in MagLev (especially CHBr 3 for high-density samples) are toxic and/or flammable. (v) To allow for measurement of water-soluble analytes, the paramagnetic metal ion must be converted into an organic-soluble chelate to give useful solubility; this transformation requires additional synthesis steps. (vi) Measurement of very low (ρ < 1.00 g/cm 3 ) and high (ρ > 3.00 g/cm 3 ) densities is complicated or difficult using simple techniques (although possible with newer...

Magnetic levitation (MagLev) provides a simple method for the separation of crystal polymorphs that differ in density (Δρ) by greater than 0.001 g cm−3. Density‐based separations of multiple crystalline forms were shown for four organic compounds: 5‐methyl‐2‐[(2‐nitro‐ phenyl)amino]‐3‐thiophenecarbonitrile, sulfathiazole, carbamazepine, and trans‐ cinnamic acid.

Magnetic levitation is a useful technique for analysis, separation and enantioenrichment of chiral/racemic products.

Supermolecules with olefins organized by hydrogen-bond donor and acceptor templates and that react in the solid state rapidly form co-crystals via solvent-free and liquid-assisted grinding.

Enlargement of a self-assembled metal-organic rhomboid is achieved via the organic solid state. The solid-state synthesis of an elongated organic ligand was achieved by a template directed [2 + 2] photodimerization in a cocrystal. Initial cocrystals obtained of resorcinol template and reactant alkene afforded a 1:2 cocrystal with the alkene in a stacked yet photostable geometry. Cocrystallization performed in the presence of excess template resulted in a 3:2 cocrystal composed of novel discrete 10-component hydrogen-bonded "superassemblies" wherein the alkenes undergo a head-to-head [2 + 2] photodimerization. Isolation and reaction of elongated photoproduct with Cu(II) ions afforded a metal-organic rhomboid of nanoscale dimensions that hosts small molecules in the solid state as guests.

A simple, flux controlled, technique to circumvent the tedium and wastage in organic synthesis is review. Pot-in-pot reactions, like matryoshka dolls, houses one reaction pot inside another.