Template-free solvothermal synthesis of hollow hematite spheres and their applications in gas sensors and Li-ion batteries

Abstract

Magnetite (Fe 3 O 4 ) hollow spheres were prepared by solvothermal reaction of ethanol solution containing Fe-acetate and L-lysine, and were subsequently transformed into hematite (Fe 2 O 3 ) hollow spheres with nanoscale (20-30 nm) thin shells by heat treatment at 500 C for 2 h. Both the as-prepared and heat-treated hollow spheres contained another small sphere within each shell, which was attributed to the following solvothermal self-assembly reactions: (1) the nucleation of Fe 3 O 4 spheres, (2) lysine capping on the nuclei, (3) the growth of lysine-capped particles by cross-linking between lysine molecules, and (4) the formation of Fe shell layers by the interaction between Fe ions and outer lysine molecules. In the assembly reaction, L-lysine with amino and carboxyl radicals played the key role. The heat-treated Fe 2 O 3 hollow spheres showed significantly enhanced C 2 H 5 OH sensing characteristics and promising Li-ion intercalation behaviors. Experimental PreparationThe Fe 3 O 4 hollow spheres were prepared by solvothermal selfassembly reaction. In 50 ml of anhydrous ethanol was dissolved 0.0870 g of iron(II) acetate (Fe(CH 3 CHOO) 2 , 99.995%, Sigma-Aldrich Co.). After adding 0.0146 g of L(+)-lysine (C

Monolayer Co3O4 Inverse Opals as Multifunctional Sensors for Volatile Organic Compounds

“…[18,19] Therefore, the selectived etection of methyl benzenes in the present study is attributed to the distinctive catalytic activity of Co 3 O 4 .R epresentative indoor air pollutantsa re volatile organic compounds such as benzene, xylene, toluene, ethanol, and HCHO. Most n-typeo xide semiconductor gas sensors show higher responses to the more reactive ethanol and HCHO [47][48][49][50][51][52] but lower responses to benzene and methylb enzenes, which have low reactivity.T hus, the selective detection of methyl benzenes with low cross-responses to ubiquitous indoor pollutants such as ethanol andH CHO in the present study is very useful for indoor pollutantm onitoring. In particular,t he operation of am onolayer Co 3 O 4 IO thin film sensora t two or three different sensing temperatures by meanso fp ulse heatingw ith different heatingv oltages can be used to discriminate between methyl benzenes and ethanol as well as to detect multiple indoor pollutant gases.…”

NO sensing by single crystalline WO3 nanowires

“…Nanostructured materials offer many advantages such as high surface-to-volume ratio, minimum power consumption, and they can be readily incorporated into microelectronic devices [11]; therefore, a transition from bulk materials [12] to thin films [13,14] and nanostructured materials [10,15,16] is taking place in the last decade. The application of nanostructured materials, such as single crystalline nanowires [17][18][19][20][21][22][23][24][25], nanotubes [26][27][28][29] and polycrystalline nanofibers [30][31][32][33][34][35], nanostructured hollow spheres [36][37][38][39] and hemispheres [40][41][42], has contributed significantly to the development of highly sensitive and selective chemical sensors.…”

Li‐ion batteries: basics, progress, and challenges

“…Again, one popular strategy is to prepare iron oxide materials in nanoscale with tailored morphologies and synthesize iron oxide/carbon composites to accommodate the volume changes as well as improve conductivity. Various iron oxides with different nanostructures have been synthesized, including nanoparticles [92], nanowires [93][94][95], nanobelts [94,96], nanorods [97][98][99], nanotubes [100,101], nanoflakes [102], nanodisks [103] and nanorings [104], nanocubes [105][106][107], nanospheres [108][109][110][111], nanospindles [108,112], nanourchins [113], and nanoflowers [103,108,[114][115][116][117][118][119]. Hollow structured iron oxides are of great interest as the space could, ideally, accommodate the volume expansion during Li insertion [108,[115][116][117][118][119].…”