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A binary oxide, polycrystalline V2O5, has been demonstrated to exhibit visible-light photochromism virtually for the first time. The oxide turns blue-black upon irradiation with visible laser light (514.5 nm) in air due to photoreduction of V⁵⁺, and this effect is confirmed to be irradiation-induced, not heat-induced. This visible-light photochromism is also demonstrated to be repeatable without significant degradation of the effect.

Phase-pure solid solutions with the composition of Sr2NbxTa2-xO7 (SNT, x = 0−2) were prepared at 900 °C for 5 h by the Pechini-type polymerizable complex (PC) technique, based upon polymerization between citric acid and ethylene glycol. The two end compounds, Sr2Ta2O7 (x = 0) and Sr2Nb2O7 (x = 2), produced H2 and O2 in a stoichiometric ratio from pure water under UV light irradiation without a NiO cocatalyst. The photocatalytic activity of SNT for the water decomposition was greatly improved by loading NiO as a cocatalyst for a whole range of x. The photocatalytic activity was dramatically decreased approximately by 1 order of magnitude once Ta has been replaced by Nb, even when the amount of Nb was small. For all of the NiO-loaded SNT samples, water was stoichiometrically decomposed into H2 and O2. While samples prior to the complete crystallization showed very low activities despite their high surface area, the corresponding photocatalytic activities of well-crystallized samples depended primarily on their surface area. The low photocatalytic activities of such premature samples were interpreted as a consequence of the increased number of lattice defects acting as inactivation centers. The maximum photocatalytic activity was obtained for NiO (0.15 wt %)/Sr2Ta2O7 prepared by the PC method at 800 °C for 48 h; the photocatalyst having a specific surface area of 10.4 m²·g^-1 produced H2 and O2 from pure water with specific rates of 3517 and 1733 μmol·h^-1·g^-1, respectively, 3.5 times larger than the best result for a sample prepared by the conventional solid-state reaction method.

Sodium niobate powders were prepared by the amorphous complex method using a water-soluble Nb−malic acid complex and sodium carbonate. Niobium oxide pentahydrate was dissolved in hot oxalic acid solution, followed by the addition of NH3 (30%) until pH = 11, precipitating niobic acid that was added into a solution of dl-malic acid (MA) at a mole ratio of [MA]:[Nb] = 2:1. Na2CO3 was added and the solvent eliminated at 70 °C, forming a yellow gel without any segregation, which was calcined at 300 °C for 3 h. The (Na−Nb−MA) material was thermally treated in the range of temperatures from 400 to 900 °C for 1 h. Although NaNbO3 was obtained at low temperature (450 °C), residual carbon was identified only by UV−Raman spectroscopy in calcined powders up to 550 °C. Crystalline phase was determined by X-ray diffractometry, and the particle size of about 100 nm was estimated from scanning electron microscopy images.

A new nanocrystalline potassium-based lithium manganese oxyiodide has been prepared by using Chimie Douce route at room temperature. According to the electrochemical measurements, this nanocrystalline sample shows a large initial capacity up to ~340 mAh/g at a constant current density of 0.2 mA/cm², which is much larger than that of sodium-based homologue. The X-ray diffraction analysis demonstrates that the amorphous character of the nanocrystalline compounds is maintained before and after chemical lithiation reaction. The local crystal structure around manganese in these materials has been determined by performing the combinative micro-Raman and X-ray absorption spectroscopy. From the Mn K-edge X-ray absorption near-edge structure and micro-Raman results, it becomes certain that manganese ions are stabilized in the rhombohedral layered lattice consisting of edge-shared MnO6 octahedra, and the crystal symmetry is changed into a monoclinic symmetry upon reaction with n-BuLi. The Mn K-edge extended X-ray fine structure analysis reveals that the structural distortion caused by lithiation process is less significant for these nanocrystalline compounds than for the spinel lithium manganate. In this context, the great discharge capacity of the nanocrystalline materials is attributable for the pillaring effect of larger alkali metal ion than lithium ion, providing an expanded interlayer space available for Li insertion. In addition, the I LI-edge X-ray absorption near-edge structure results presented here make it clear that iodine is stabilized as iodate species on the grain boundary or the surface of the nanocrystalline manganese oxyiodide, which helps to maintain the nanocrystalline nature of the present materials before and after Li insertion.

PbZrO3 (PZ) nanoparticles were synthesized through a halide- and organic-free hydrogen peroxide method at 700 °C for 2 h. Stoichiometric amounts of zirconyl nitrate and lead nitrate were dissolved in a diluted H2O2 (aqueous) solution, which was slowly dropped into a solution of H2O2 and NH3 (pH = 11). The precipitate of Pb−Zr, obtained from an exothermic oxy-reduction reaction, was filtered and washed to eliminate all nitrate ions. The precipitate was dried, ground, and calcined between 300 and 1000 °C, for 5 min to 8 h. Tetragonal, lead-rich zirconia solid solution (t-Z) was identified by thermogravimetry−differential thermal analysis, X-ray diffraction, and Raman spectroscopy as an intermediate phase during the calcination process, followed by the crystallization of the orthorhombic PZ phase. The average particle size was estimated to be 50 nm from scanning electron microscopy pictures. The change in the amount of residual t-Z phase in PZ powders was estimated from the Raman spectra.

Lithium niobate powders were prepared from LiCl and a new water-soluble complex synthesized with dl-malic acid (MA) and NbCl5, using neither dry solvents nor an inert atmosphere. A stable aqueous solution was prepared containing niobium chloride and MA, with a molar ratio of [MA]:[Nb] = 2:1 at pH = 7. UV−Raman spectroscopy of the Nb−MA aqueous solution indicated the coordination of the Nb with the deprotonated alcohol and with the carboxylic groups of the MA molecule. Continuous heating of a mixed aqueous solution containing MA, ammonia, Li, and Nb ions at 70 °C produced a pale yellow powder which was heat treated at 350 °C for 5 h to sublimate NH4Cl, eliminating more than 99.5 wt % of the chlorine. The Nb−Li−MA heated-treated powder was calcined under different conditions of temperature and time. The formation of pure LiNbO3, free from amorphous carbon, which occurred at temperatures greater than 650 °C, was confirmed by a combined analysis using X-ray diffraction and UV−Raman spectroscopy.

PbTiO3 has been successfully synthesized at reduced temperatures (500−700 °C) using neither organics (including alkoxides) nor undesirable halides. Water-soluble peroxytitanic complexes [Ti(OH)3O2]^- were prepared by the reaction between titanium metal and hydrogen peroxide at pH = 11. A solution of lead nitrate was added to the peroxytitanic acid solution and an amorphous precipitate of lead and titanium was formed, which was filtered and washed to eliminate the nitrate ion. The precipitate was calcined between 200 and 700 °C in a closed alumina boat. The precipitate was characterized by ICP, TG, Raman spectroscopy, XRD, and SEM, and the calcined lead titanate was characterized by BET, Raman spectroscopy, XRD, and SEM. The amorphous precipitate showed a small weight loss (11.45%). Powders calcined at temperatures higher than 500 °C showed pure tetragonal PbTiO3 perovskite phase on the XRD patterns and Raman spectra and a large surface area in the range of 6−22 m² g^-1. The average diameter of the particles was calculated from the SEM image as 100 nm.

A novel tantalic acid-based polymerizable complex (PC) route to LiTaO3 was developed that uses neither alkoxides nor chlorides of Ta. Moisture-insensitive Ta2O5 was chosen as a starting source of Ta, and it was converted to a Ta−oxalate solution by means of the classic KHSO4−oxalic acid method of Schoeller. Tantalic acid precipitated upon addition of ammonia solution to the Ta−oxalate solution. The freshly precipitated tantalic acid was soluble in a hot oxalic acid aqueous solution, and it was quite stable against hydrolysis. This water-resistant Ta precursor mixed with citric acid (CA), ethylene glycol (EG), and Li2CO3 was polymerized at 130 °C to produce a yellowish transparent polyester-type resin without undergoing precipitation, which after decomposition on heating at 350 °C was used as a powder precursor for LiTaO3. Phase-pure LiTaO3 in powder form was successfully synthesized at a reduced temperature (500 °C). The final LiTaO3 powder calcined at 500−700 °C had a considerably large surface area in the range of 22−37 m²/g when compared with 1.4 m²/g for the conventional solid-state reaction powder of the same compound.

Precursor solutions containing citric acid (CA), ethylene glycol (EG), and barium and titanium ions, previously used in the Pechini-type polymerizable complex (PC) processing of BaTiO3, have been extensively characterized by Raman and ¹³C NMR spectroscopy. The simultaneous presence of Ba and Ti ions has brought about the unusual dissociation of proton from the alcohol OH group of CA, thereby creating an alkoxide oxygen atom with a strong nucleophilic nature, which prompts rearrangement of CA to form a barium−titanium mixed-metal CA complex with a stoichiometry close to Ba/Ti/CA = 1:1:3. The solution spectroscopy data have been compared with those obtained for an isolated mixed-metal CA complex from a solution with a chemical formula of BaTi(C6H6O7)3·4H2O. The Raman spectrum of BaTi(C6H6O7)3·4H2O has shown that the two terminal COOH groups of each CA coordinate in a monodentate fashion either to Ba or to Ti, while the central COOH group is not coordinating. The solid-state ¹³C NMR spectrum of the same complex has indicated that the alcohol OH in CA is fully deprotonated to form an alkoxide oxygen atom, in agreement with the solution ¹³C NMR data. A proposed model for the coordination structure of BaTi(C6H6O7)3 species, inferred from all these spectroscopic data, has displayed the presence of three fused six-memberd chelate rings arising from the full alkoxylation of CA ligands.

Phase-pure BaTi4O9 powders were prepared at temperatures higher than 700 °C by the Pechini-type polymerizable complex (PC) technique, based upon polyesterification between citric acid and ethylene glycol. BaTi4O9 was subsequently converted to nanocomposite materials by modifying its surface with ultrafine particles of RuO2, and the nanocomposite was used as photocatalyst for the decomposition of water into H2 and O2. The RuO2/PC-BaTi4O9 material prepared at 800 °C showed a photocatalytic activity ~5 times higher than that of a sample prepared by a solid-state reaction at 1100 °C. The activity did not scale simply with the specific surface area of the samples; e.g. the sample having a surface area of 20.4 m²/g (prepared at 700 °C ) showed, unexpectedly, a ~50% reduction in the activity when compared with that of a sample having a surface area of 7.6 m²/g (prepared at 800 °C ). The anomalous reduction in the activity was interpreted as a consequence of the increased number of lattice defects acting as inactivation centers. The average emission lifetime estimated from an emission decay curve decreased from 4.0 to 2.5 ns with a decrease in the preparation temperature from 900 to 700 °C, suggesting that the number of lattice defects is increased as the temperature is lowered.

To investigate the effects of enalapril, an angiotensin-converting enzyme inhibitor, on nitrate tolerance during continuous nitrate therapy, coronary artery diameters and platelet cyclic guanosine monophosphate (cGMP) levels were measured before and 2 minutes after intracoronary injection of nitroglycerin 200 @mg in 60 patients with coronary artery disease and were compared among 20 patients treated with nitrates (nitrate group), 20 patients treated with both nitrates and enalapril (enalapril group), and 20 untreated patients (control group). The percent increase in platelet cGMP and coronary dilatation in the nitrate group was significantly less than in the control group, but the percent increase in the enalapril group was significantly greater than that in the nitrate group. These results indicate that enalapril may be helpful as concomitant therapy to maintain the effect of nitrates during continuous nitrate therapy. (Am Heart J 1997;134:614-21.)

A polymerized complex (PC) technique was applied to the preparation of a highly active photocatalyst, K2La2Ti3O10, with a layered perovskite type structure to decompose H2O into H2 and O2. The catalyst prepared by the PC technique had a higher photocatalytic activity than that prepared by conventional solid-state reaction method.

Perovskite PbTiO3 powders were prepared by a polymerized complex technique at relatively low temperatures, viz. 400−600 °C. Heating of a mixed solution of citric acid (CA), ethylene glycol (EG), and Pb and Ti ions with a molar ratio of Pb/Ti/CA/EG = 1/1/10/40 at 130 °C produced a yellowish transparent polymeric gel without any precipitation, which after pyrolysis at 300 °C was converted to a powder precursor for PbTiO3. We suggest, based on the results of Raman and ¹³C NMR spectroscopies, that a heterometallic (Pb,Ti)−CA3 chelate complex formed in a starting Pb/Ti/CA/EG solution and it was thermally stable upon polymerization at 130 °C. Chemical analyses showed no PbO loss during calcination of powder precursors at 400−700 °C, which led to the conclusion that a solid-state reaction between isolated PbO and TiO2 particles was not responsible for PbTiO3 formation, but PbTiO3 formed directly by thermal decomposition of the powder precursor above 400 °C.