This study describes the development of a mild room-temperature chemical dehydration method that effectively removes water from fragile living botanical leaf species without collapsing or physically degrading their macrostructure. The dehydrated plant materials retain an extensive vascular and cellular structure that was subsequently used as templating surfaces for metal oxide growth. The facile room-temperature chemical dehydration process used 2,2-dimethoxypropane (DMP) in acid-catalyzed reactions with water to yield methanol and acetone. The resulting chemically dehydrated botanical materials are relatively robust and retain their intricate internal cellular and vascular structures with little reduction in physical size despite the removal of over 70% of their original mass. Dehydrated botanical templates from several different leaf species were used to produce titania and silica structures. Water reactive titanium and silicon alkoxide precursors were incorporated into the DMP dried templates through a simple benchtop liquid absorption method. Subsequent hydrolysis, pyrolysis, and calcination in air removed the template’s cellulose framework and yielded crystalline anatase TiO2 at 475 °C or crystobalite SiO2 at 1000 °C. The oxide monoliths retain large portions of the original plant’s macroscopic and microscopic cellular structure. Challenges related to using botanical materials as inorganic structure templates are highlighted. DMP dehydration methods provide access to a potentially very diverse set of living botanical species as templates to inorganic materials with nature-inspired structures.Keywords: chemical dehydration; precursor; silica; templating; titania;

We report a straight-forward, solvent-free moderate temperature synthetic method for the production of several phosphorus-rich transition-metal phosphides (orthorhombic FeP2, cubic CoP3, cubic NiP2, monoclinic CuP2, and monoclinic PdP2). Notably, this synthetic approach provides facile access to the high-temperature/high-pressure cubic phase of NiP2. The general synthetic strategy involves the direct reaction of anhydrous metal dichloride pressed pellets with molecular P4 vapor or solid−solid reactions between the metal dichloride and red phosphorus that are intimately mixed into pellets. Both of these reaction strategies involve the evolution of a volatile PCl3 byproduct and produce crystalline MPx (x ≥ 2) at moderate temperatures of 500−700 °C. The pellets remain intact throughout the synthesis, and the macrostructure of the MPx products resembles that of the reactant pellets. By varying the phosphorus source, the percentage of the pellet precursor mass that is retained in the final metal phosphide pellet products changes, which influences the morphology and microstructure of the final phosphide pellet.

This paper describes the use of solvothermally moderated metal azide decomposition as a route to nanocrystalline mid to late transition metal nitrides. This method utilizes exothermic solid-state metathesis reaction precursor pairs, namely, metal halides (NiBr2, FeCl3, MnCl2) and sodium azide, but conducts the metathesis reaction and azide decomposition in superheated toluene. The reaction temperatures are relatively low (<300 °C) and yield thermally metastable nanocrystalline hexagonal Ni3N and Fe2N, and tetragonal MnN. These solvothermally moderated metal nitride metathesis reactions require several days to produce high yields of the intended nitrides. The products are aggregated nanoparticulates with room temperature magnetic properties consistent with their known bulk structures, for example, Fe2N and Ni3N are known ferromagnets. The stirred reactions with dispersed fine reagent powders benefit from solvothermal moderation more effectively than submerged pressed reagent pellets. Pellet reactions produced manganese nitrides with lower nitrogen content and higher aggregation than loose powder reactions, consistent with the occurrence of significant local exothermic heating in the pellet metathesis reactions.

Nanocrystalline InN powders have been synthesized through metal azide decomposition in superheated toluene and refluxing hexadecane solvents near 280 °C. The metal azide intermediates were formed in situ through the metathesis reaction of InBr3 and NaN3. The InN products from toluene consist of ∼10 nm hexagonal (wurtzite) structured crystallites in aggregated arrangements. InN from hexadecane and lower temperature toluene reactions produced more poorly crystalline InN that appears to contain a cubic (zinc blende) component. Coordinating amine solvents led to decomposition of the nitride to indium metal. Several reactions were undertaken to produce mixed metal nitrides of the form Ga1−zInzN where z is 0.5 and 0.75. The mixed metal nitride products are analytically consistent with composite versus solid-solution formation, however some metal mixing is observed. Data from X-ray diffraction, electron microscopy, thermal analysis, elemental analysis, and several spectroscopic methods are combined to form a consistent picture of the bulk and surface structures for these nanocrystalline InN materials.

The solid-state hydrolysis and air calcination of aluminum-doped TiCl3 leads to crystalline anatase TiO2 that is stable on heating to 1000 °C, in contrast to control studies with related AlCl3 and TiCl3 physical mixtures that produce rutile TiO2 under the same conditions.

Many transition-metal azides are thermodynamically unstable with respect to the elements and thus, may serve as energetic precursor sources in nanoscale metal particle synthesis. This report describes the use of silver azide (AgN3) in nonaqueous, solvothermal decomposition reactions to produce crystalline sub-micron silver particles and interconnected structures. The thermal decomposition of AgN3 directly produces silver and N2 and no secondary chemical reducing agent is required. This solvothermal conversion was examined in toluene, tetrahydrofuran (THF), and trioctylamine below 250 °C. The coordinating solvents produced the smallest particles (150–500 nm), while the toluene reaction products were near 1 μm in size. The addition of soluble elemental sulfur to the THF reaction results in the growth of silver sulfide particles near 1 μm in size. The silver and Ag2S products are crystalline by X-ray diffraction and show some faceting by scanning electron microscopy.

There is increasing interest in high surface area carbon nitride materials as potential coordinatively active analogs of amorphous carbon systems. It is generally difficult to produce extended carbon structures with high nitrogen contents. This article describes a facile molecular decomposition process that produces bulk quantities of an amorphous nitrogen-rich carbon nitride material, C3N4+x where 0.5 < x < 0.8, in only a few seconds without the use of complex experimental apparatus. The trichloromelamine molecular precursor [(C3N3)(NHCl)3] rapidly decomposes when heated externally above 185 °C or when brought into contact with a heated filament. Morphological studies show that the rapid synthesis process produces a porous, sponge-like material containing spherical nanofeatures (<300 nm). These amorphous carbon nitrides were analyzed by IR, NMR, optical, and X-ray photoelectron spectroscopy, which indicate that the carbon centers have primarily sp2 hybridization, triazine (C3N3) rings are retained in the product, and nitrogen species bridge triazines. These C3N4+x materials are also luminescent in the blue region even after annealing to 400 °C. They exhibit thermal and chemical stability with no significant decomposition until 600 °C or reactivity with concentrated aqueous base.

We report the lowest-temperature chemical vapor deposition process for the growth of amorphous carbon nitride (CNx) films. The precursor, triazidotriazine or (C3N3)(N3)3, contains only CN or NN bonds, and evaporates and decomposes to carbon nitride films by 250 °C. Infrared and X-ray photoelectron spectroscopy (XPS) show that the amorphous films have primarily sp2-bonded structures with some retention of the precursor aromatic triazine ring (C3N3) character. Auger and XPS results show that the film composition is near CN1.5 (C3N4.5). Electron microscopy demonstrates that the CNx films have small particle domains near 50 nm and some porosity. The films exhibit strong UV absorption and weak photoluminescent emission below 500 nm.