In-situ transmission electron microscopy of liposomes in an aqueous environment.

The characterization of liposomes was undertaken using in-situ microfluidic transmission electron microscopy. Liposomes were imaged without contrast enhancement staining or cryogenic treatment, allowing for the observation of functional liposomes in an aqueous environment. The stability and quality of the liposome structures observed were found to be highly dependent on the surface and liposome chemistries within the liquid cell. The successful imaging of liposomes suggests the potential for the extension of in-situ microfluidic TEM to a wide variety of other biological and soft matter systems and processes.

Synthesis and structural characterization of a family of modified hafnium tert-butoxide for use as precursors to hafnia nanoparticles.

A series of modified, hafnium tert-butoxide ([Hf(OBu(t))4]) compounds (1-26) were crystallographically characterized, and representative species were then used to produce HfO2nanoparticles. This systematically varied family of [Hf(OR)4] compounds was developed from the reaction of [Hf(OBu(t))4] with a series of (i) Lewis basic solvents, tetrahydrofuran, pyridine, or 1-methylimidazole; (ii) simple phenols, HOC6H4(R)-2 or HOC6H3(R)2-2,6 where R = CH3, CH(CH3)2, or C(CH3)3; and (iii) complex polydentate alcohols, tetrahydrofuran methanol (H-OTHF), pyridinecarbinol (H-OPy), and tris(hydroxymethylethane) (THME-H3). The solvent-modified products were crystallographically characterized as [Hf(OBu(t))4(solv)n] (1-3). The phenoxide (OAr)-exchanged [Hf(OBu(t))4] products isolated from toluene were characterized as dimeric [Hf(OAr)n(OBu(t))4-n]2 (4 and 5) or [Hf(µ-OH)(OAr)3(HOBu(t))]2 (6 and 7) for the less sterically demanding OAr ligands and [Hf(OAr)n(OBu(t))4-n(HOBu(t))] (8 and 9) monomers for the larger OAr ligands. When Lewis basic solvents were employed, solvated monomers of varied OAr substitutions were observed as [Hf(OAr)n(OBu(t))4-n(solv)x], where solv = THF (10, 11, and 13-15) and py (16 and 19-21). The nuclearities of the remaining complex polydentate alcohol derivatives ranged from monomers (24, OPy) to dimers (22, OTHF; 23, OPy) to tetramers (25 and 26, THME). On the basis of their nuclearities, select members of this family of [Hf(OR)4] compounds (monomer, [Hf(OBu(t))4], 8; dimer, 19a, 22; tetramer, 25) were used to determine the validity of using [Hf(OR)4] precursors for the production of hafnia (HfO2) nanoparticles under solvothermal (oleylamine/oleic acid) conditions. After a 650 °C thermal treatment, the resulting powder X-ray diffraction pattern for each powder was found to be consistent with HfO2 (PDF 00-040-1173), and after a 1000 °C treatment, larger particles of HfO2 (PDF 00-043-1017) were reported. Transmission electron microscopy images confirmed that nanomaterials had formed. Because identical processing conditions had been employed for each HfO2 nanomaterial, the morphological variations observed in this study may be attributed to the individual precursors ("precursor structure affect").

Tin(II) amide/alkoxide coordination compounds for production of Sn-based nanowires for lithium ion battery anode materials.

A series of tin(II) amide alkoxides ([(OR)Sn(NMe(2))](n)) and tin(II) alkoxides ([Sn(OR)(2)](n)) were investigated as precursors for the production of tin oxide (SnO(x)) nanowires. The precursors were synthesized from the metathesis of tin dimethylamide ([Sn(NMe(2))(2)](2)) and a series of aryl alcohols {H-OAr = H-OC(6)H(4)(R)-2: R = CH(3) (H-oMP), CH(CH(3))(2) (H-oPP), C(CH(3))(3) (H-oBP)] or [H-OC(6)H(3)(R)(2)-2,6: R = CH(3) (H-DMP), CH(CH(3))(2) (H-DIP), C(CH(3))(3) (H-DBP)]}. The 1:1 products were all identified as the dinuclear species [(OAr)Sn(µ-NMe(2))](2) where OAr = oMP (1), oPP (2), oBP (3), DMP (4), DIP (5), DBP (6). The 1:2 products were identified as either a polymer ([Sn(µ-OAr)(2)](∞) (where OAr = oMP (7), oPP (8)), dinuclear [(OAr)Sn(µ-OAr)](2) (where OAr = oBP (9), DMP (10) or DIP/HNMe(2) (11)), or mononuclear [Sn(DBP)(2)] (12) complexes. These novel families of compounds (heteroleptic 1-6, and homoleptic 7-12) were evaluated for the production of SnO(x) nanowires using solution precipitation (SPPT; oleylamine/octadecene solvent system) or electrospinning (ES; THF solvent) processing conditions. The SPPT route that employed the heteroleptic precursors yielded mixed phases of Sn(o):romarchite [1 (100:0); 2 (80:20); 3 (68:32); 4 (86:14); 5 (66:35); 6 (88:12)], with a variety of spherical sized particles [1 (350-900 nm); 2 (150-1200 nm); 3 (250-950 nm); 4 (20-180 nm); 5 (80-400 nm); 6 (40-200 nm)]. For the homoleptic precursors, similar phased [7 (80:20); 8 (23:77); 9 (15:85); 10 (34:66); 11 (77:23); 12 (77:23)] spherical nanodots were isolated [7 (50-300 nm); 8: (irregular); 10 (200-800 nm); 11 (50-150 nm); 12 (50-450 nm)], except for 9 which formed polycrystalline rods [Sn(o):romarchite (15:85)] with aspect ratios >100. From ES routes, the heteroleptic species were found to form 'tadpole-shaped' materials whereas the homoleptic species formed electrosprayed nanodots. The one exception noted was for 7, where, without use of a polymer matrix, nanowires of Sn(o), decorated with micron sized 'balls' were observed. Due to the small amount of material generated, PXRD patterns were inconclusive to the identity of the generated material; however, cyclic voltammetry on select samples was used to tentatively identify the final Sn(o) (from 7) with the other sample identified as SnO(x) (from 1).

Thermally tunable surface wettability of electrospun fiber mats: polystyrene/poly(N-isopropylacrylamide) blended versus crosslinked poly[(N-isopropylacrylamide)-co-(methacrylic acid)].

This work reports on thermally tunable surface wettability of electrospun fiber mats of: polystyrene (PS)/poly(N-isopropylacrylamide) (PNIPA) blended (bl-PS/PNIPA) and crosslinked poly[(N-isopropylacrylamide)-co-[methacrylic acid)] (PNIPAMAA) (xl-NIPAMAA). Both the bl-PS/PNIPA and xl-PNIPAMAA fiber mats demonstrate reversibly switchable surface wettability, with the bl-PS/PNIPA fiber mats approaching superhydrophobic ≥150° and superhydrophilic contact angle (CA) values at extreme temperatures. Weight loss studies carried out at 10 °C indicate that the crosslinked PNIPAMAA fiber mats had better structural integrity than the bl-PS/PNIPA fiber mats. PNIPA surface chemistry and the Cassie-Baxter model were used to explain the mechanism behind the observed extreme wettability.

Synthesis, characterization, and electrochemical properties of a series of sterically varied iron(II) alkoxide precursors and their resultant nanoparticles.

A new family of iron(II) aryloxide [Fe(OAr)(2)(py)(x)] precursors was synthesized from the alcoholysis of iron(II) mesityl [Fe(Mes)(2)] in pyridine (py) using a series of sterically varied 2-alkyl phenols (alkyl = methyl (H-oMP), isopropyl (H-oPP), tert-butyl (H-oBP)) and 2,6-dialkyl phenols (alkyl = methyl (H-DMP), isopropyl (H-DIP), tert-butyl (H-DBP), phenyl (H-DPhP)). All of the products were found to be mononuclear and structurally characterized as [Fe(OAr)(2)(py)(x)] (x = 3 OAr = oMP (1), oPP (2), oBP (3), DMP (4), DIP (5); x = 2 OAr = DBP (6), DPhP (7)). The use of tris-tert-butoxysilanol (OSi(OBu(t))(3) = TOBS) led to isolation of [Fe(TOBS)(2)(py)(2)] (8). The new Fe(OAr)(2)(py)(x) (1-6) were found, under solvothermal conditions, to produce nanodots identified by PXRD as the γ-maghemite phase. The model precursor 3 and the nanoparticles 6n were evaluated using electrochemical methods. Cyclic voltammetry for 3 revealed multiple irreversible oxidation peaks, which have been tentatively attributed to the loss of alkoxide ligand coupled with the deposition of a solid Fe-containing coating on the electrode. This coating was stable out to the voltage limits for the acetonitrile solvent.

Series of comparable dinuclear group 4 neo-pentoxide precursors for production of pH dependent group 4 nanoceramic morphologies.

A series of similarly structured Group 4 alkoxides was used to explore the cation effect on the final ceramic nanomaterials generated under different pH solvothermal (SOLVO) conditions. The synthesis of [Ti(µ-ONep)(ONep)(3)](2) (1, ONep = OCH(2)C(CH(3))(3)) and {[H][(µ-ONep)(3)M(2)(ONep)(5)(OBu(t))]} where M = Zr (2) and Hf (3, OBu(t) = OC(CH(3))(3)) were realized from the reaction of M(OBu(t))(4) (M = Ti, Zr, Hf) and H-ONep. Crystallization of 1 from py led to the isolation of [Ti(µ-ONep)(ONep)(3)](2)(µ-py) (1a) whereas the dissolution of 2 or 3 in py yielded {(µ(3)-O)(µ(3)-OBu(t))[(µ-ONep)M(ONep)(2)](3)} M = Zr (2a) and Hf (3a). The structurally similar congener set of 1-3 was used to investigate variations of their resultant nanomaterials under solvothermal conditions at high (10 M KOH), low (conc. (aq) HI), and neutral (H(2)O) pH conditions. Reproducible nanodots, -squares, and -rods of varied aspect ratios were isolated based on cation and the reaction pH. The hydrolysis products were reasoned to be the "seed" nucleation sites in these processes, and studying the hydrolysis behavior of 1-3 led to the identification of [Ti(6)(µ(3)-O)(7)(µ-O)(µ-ONep)(2)(ONep)(6)](2) (1b) for 1 but yielded 2a and 3a for 2 and 3, respectively. A correlation was found to exist between these products and the final nanomaterials formed for the acidic and neutral processes. The basic route appears to be further influenced by another property, possibly associated with the solubility of the final nanoceramic material.