Yixing Ye

A novel reduction approach to fabricate quantum-sized SnO2-conjugated reduced graphene oxide nanocomposites as non-enzymatic glucose sensors

Quantum-sized SnO2 nanocrystals can be well dispersed on reduced graphene oxide (rGO) nanosheets through a convenient one-pot in situ reduction route without using any other chemical reagent or source. Highly reactive metastable tin oxide (SnO(x)) nanoparticles (NPs) were used as reducing agents and composite precursors derived by the laser ablation in liquid (LAL) technique. Moreover, the growth and phase transition of LAL-induced SnO(x) NPs and graphene oxide (GO) were examined by optical absorption, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and high-resolution transmission electron microscopy. Highly dispersed SnO(x) NPs can also prevent rGO from being restacked into a multilayer structure during GO reduction. Given the good electron transfer ability and unsaturated dangling bonds of rGO, as well as the ample electrocatalytic active sites of quantum-sized SnO2 NPs on unfolded rGO sheets, the fabricated SnO2-rGO nanocomposite exhibited excellent performance in the non-enzymatic electrochemical detection of glucose molecules. The use of LAL-induced reactive NPs for in situ GO reduction is also expected to be a universal and environmentally friendly approach for the formation of various rGO-based nanocomposites.

Reduced graphene oxide anchored magnetic ZnFe2O4 nanoparticles with enhanced visible-light photocatalytic activity

We report a facile approach to immobilize magnetic ZnFe2O4 nanoparticles (NPs) onto a reduced grapheme oxide (rGO) network by using highly reactive ZnOx(OH)y and FeOx colloids as precursors, which were respectively obtained by laser ablation of metallic zinc (Zn) and iron (Fe) targets in pure water. A microstructure investigation of such nanocomposites (NCs) revealed that ZnFe2O4 NPs are well-dispersed onto rGO sheets. Such a structure was helpful for separating the photoexcited electron–hole pairs and accelerating the electrons transfer. Electrochemical impedance measurements indicated the remarkable decrease of the interfacial layer resistance of the composite structure compared to that of pure ZnFe2O4 NPs. As a result of these advantages, such NCs present a prominent enhancement in the photodegradation efficiency for methylene blue dye. Besides, the excellent magnetic properties of the ZnFe2O4 NPs allow the catalysts to be easily separated from the solution by a magnet for recycling. This effort not only provided a new approach to fabricate ZnFe2O4–rGO NCs, also expanded the application of ZnFe2O4 NPs used as visible-light excited photocatalysts in application of organic pollutants degradation.

In situ growth of lamellar ZnTiO3 nanosheets on TiO2 tubular array with enhanced photocatalytic activity

We report a self-sacrificed in situ growth design toward preparation of ZnTiO3-TiO2 heterojunction structure. Highly reactive zinc oxide colloidal particles derived by laser ablation in liquids can react with TiO2 nanotubes to form a lamellar ZnTiO3 nanosheet structure in a hydrothermal-treatment process. Such hybrid structural product was characterized by X-ray diffraction, scanning and transmission electron microscopy, UV-vis diffuse reflection spectroscopy and X-ray photoelectron spectroscopy. The enhanced photocatalytic activity of the hybrid structure toward degradation of methyl orange (MO) and pentachlorophenol (PCP) molecules was demonstrated and compared with single phase TiO2, as a result of the efficient separation of light excited electrons and holes at the hetero-interfaces in the two semiconductors.

Synthesis of Mn-doped α-Ni(OH)2 nanosheets assisted by liquid-phase laser ablation and their electrochemical properties

We designed a new strategy, namely, the laser ablation of a target material in an aqueous ionic solution, to prepare Mn-doped Ni(OH)2 nanosheets based on reactions between the pulsed laser-induced plasma plume of Mn and the surrounding NiCl2 solution. The crystalline phase, morphology and structure of the as-derived products are characterised by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Results indicate the hierarchical assembly of numerous tiny nanosheet building blocks into a Mn-doped α-Ni(OH)2 spherical structure. Importantly, the positive electrode made of Mn-doped α-Ni(OH)2 nanosheets exhibits a high specific capacitance of ~1000 F g(-1) under a current density of 5 A g(-1), concurrently possessing excellent cycling ability. This novel strategy may offer researchers an alternative for designing interesting solid targets and ionic solutions towards the fabrication of other new nanostructures for fundamental research and potential applications.

Layered mesoporous Mg(OH)2/GO nanosheet composite for efficient removal of water contaminants

A layered magnesium hydroxide (Mg(OH)2) nanosheet/graphene oxide (GO) composite was synthesized through laser ablation of the Mg target in an aqueous solution with GO. Its mesoporous structure and application as an adsorbent for the removal of methylene blue (MB) and heavy metal ions from water were investigated. Mg(OH)2 nanosheets were organized in situ from the strong reaction between the laser-ablated Mg species and water molecules. The GO nanosheet served as a heterogeneous nucleation and growth site for sheet-like Mg(OH)2 nanocrystals. The resulting porous Mg(OH)2/GO nanosheet composite had a high specific surface area of 310.8 m2 g−1 and a pore volume of 1.031 cm3 g−1. These characteristics show that the composite could be an excellent adsorbent. The composite exhibited a maximum adsorption capacity of 532 mg g−1 at 298 K for typical contaminants of MB, and over 300 mg g−1 for heavy metal ions Zn2+ and Pb2+.

Simultaneous doping and growth of Sn-doped hematite nanocrystalline films with improved photoelectrochemical performance

Hematite is an important material used in water splitting and lithium-ion battery electrodes. Electronic conductivity and the visible light-absorption ability of hematite are enhanced by doping impurity ions into the hematite lattice and achieving an appropriate hematite nanostructure. This paper reports the simultaneous doping and growth of tin (Sn)-doped hematite crystalline films on a conducting substrate. The crystalline films were prepared by a hydrothermal process. Laser ablation in liquid induced SnOx colloidal nanoparticles, which were used as the doping source. The obtained compacted films were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and UV-vis spectrophotometry analyses. XRD results showed the Sn-doped α-Fe2O3 crystalline nanoparticles had dominant active (110) planes. Annealing affected the photoelectrochemical (PEC) performance of the Sn-doped hematite photoanode, and the photocurrent density of the photoanode annealed at 750 °C for 2 h reached the highest value at 0.48 mA cm−2 (at 1.23 V vs. reversible hydrogen electrode). Electrochemical impedance spectroscopy measurements revealed that the charge-transfer resistance of Sn-doped hematite films decreased after the annealing treatment. The improved crystallinity and the preferred (110) plane in the doped crystalline film are favor of the migration of electrons and holes to electrode surfaces, the removal of deleterious surface states and increase of the free electron density, which should contribute to the enhanced PEC performance.

Structural and electrochemical evaluation of a TiO2-graphene oxide based sandwich structure for lithium-ion battery anodes

In this paper, we report a rational sandwich composite structure consisting of polyaniline (PANI), amorphous TiO2 (a-TiO2), and a GO network as an anode material for lithium-ion batteries (LIBs). After the synthesis of the a-TiO2–GO composite assisted by laser ablation in liquid, PANI nanorods are vertically grown on the both sides of a-TiO2–GO nanosheets to obtain a stable sandwich structure. The morphology and components of the composites are confirmed by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. As a typical anode material in LIBs, the fabricated sandwich composites display a high rate capability and long cycle life. A first discharge capacity of 1335 mA h g−1 is shown at 50 mA g−1 and a reversible capacity of 435 mA h g−1 is achieved after 250 cycles at 100 mA g−1. Even at a high cycling rate of 10 A g−1, the sandwich products exhibit a stable capacity of 141 mA h g−1. This effort highlights the design of a sandwich structure using amorphous TiO2, GO, and PANI nanorods and its potential benefits for LIB application.

Aqueous dispersed ablated bismuth species and their potential as colloidal Bi precursors in synthetic strategies

Intense scientific efforts have been focused on the exploration of the unusual physical and chemical properties of colloidal nanoparticles (NPs). Here, surfactant-free ablated bismuth colloidal species showing distinctive advantages of high reactivity and reducibility were generated by laser-ablating metal Bi in deionized water. They can further react with water molecules and display self-assembly behaviour to form Bi(OH)3 nanowires at ambient condition. Interestingly, under aging at 60 °C or light irradiation, Bi-based colloids will tend to react and self-assemble into phases of Bi2O3 and Bi2O4 nanocrystals. Furthermore, various bismuth-containing compounds, such as bismuth oxyhalides (BiOX, X = Cl, Br, I), Ag/Au/Pt-modified BiOCl, BiVO4, and Bi2WO6 semiconductors were also successfully produced through the reaction of ablated bismuth colloidal species with corresponding chemical reagents or with ablated V and W colloidal species. These synthetic strategies proved that LAL-induced colloidal species are capable of serving as unique chemical precursors. The relatively slow, dynamic species-by-species reaction greatly favours controllable growth and tunable nanostructure compared with the conventional rapid ion-by-ion reaction. Importantly, this growth route provides more underlying insights regarding the growth and assembly mechanisms of nanocrystals without influence from additional chemical ions or surfactants.

Monodispersed carbon nanodots spontaneously separated from combustion soot with excitation-independent photoluminescence

We present a facile, low-cost procedure by simple one-step combustion of small organic molecules to obtain ultrafine, hydrophobic, and fluorescent carbon nanodots (CNDs). Without further centrifugation and dialysis, we could easily separate CNDs from combustion soot through spontaneous sedimentation. Transmission electron microscopy and photoluminescence characterization demonstrated that the collected CNDs possessed a monodispersed size distribution with a diameter of 1.9 ± 0.5 nm and excitation-independent luminescence properties. Furthermore, after oxidization treatment, the oxidized CNDs displayed good water solubility and the highest fluorescence intensity in neutral solution.

Strong Fe 3+ -O(H)-Pt Interfacial Interaction Induced Excellent Stability of Pt/NiFe-LDH/rGO Electrocatalysts

Agglomeration-triggered deactivation of supported platinum electrocatalysts markedly hinders their application in methanol oxidation reaction (MOR). In this study, graphene-supported nickel–iron layered double hydroxide (NiFe-LDH/rGO), in which Fe3+ was introduced to replace Ni2+ partially in the Ni(OH)2 lattice to provide stronger metal–support bonding sites, was utilized to immobilize Pt nanoparticles (NPs). Given the optimized metal–support interfacial contact (Fe3+-O(H)-Pt) between Pt NPs and NiFe-LDH/rGO nanosheets for Pt/NiFe-LDH/rGO electrocatalysts, the Pt/NiFe-LDH/rGO electrocatalysts displayed dramatically enhanced durability than that of Pt/Ni(OH)2/rGO counterpart as well as commercial Pt/C, and 86.5% of its initial catalytic activity can be maintained even after 1200 cycles of cyclic voltammetry (CV) tests during MOR. First-principle calculations toward the resultant M-O(H)-Pt (M = Fe3+, Ni2+) interfacial structure further corroborates that the NiFe-LDH nanosheets can provide stronger bonding sites (via the Fe3+-O(H)-Pt bonds) to immobilize Pt NPs than those of Ni(OH)2 nanosheets (via the Ni2+-O(H)-Pt bonds).