Surface protolytic property characterization of hydroxyapatite and titanium dioxide nanoparticles

We provide characterization data of hydroxyapatite (nHAp) and titanium dioxide (nTiO₂) nanoparticles as potential materials for ion sorption, e.g. in targeted therapy, barrier materials for waste repositories or photovoltaics. The study is focused on the determination of the values of protonation and ion exchange constants and site densities (∑SOH, ∑X; [mol kg⁻¹]) of nTiO₂ and nHAp for further Ra kinetics and sorption experiments. These data are very important for further investigation of the materials, which can be used e.g. as drug delivery systems or in engineered barriers of deep geological repositories. The characterization was based on the evaluation of the dependence of titrating agent consumption on pH. Titration results were evaluated on the basis of several model combinations, however the combination of the Chemical Equilibrium Model (CEM) and Ion Exchange Model (IExM) fits best to the experimental titration curves. However, the differences between the two sorbents were relatively large. Due to stability in a broad pH range and available surface sites, nTiO₂ seems to have a wide application range. The applicability of nHAp is not so wide because of its dissolution under pH 5. Both sorbents are virtually able to sorb cationic species on deprotonated edge and layer sites with different capacities, which can be important for sorption and decontaminating applications.

We provide characterization data of hydroxyapatite (nHAp) and titanium dioxide (nTiO₂) nanoparticles as potential materials for ion sorption, e.g. in targeted therapy, barrier materials for waste repositories or photovoltaics.     

New insights for titanium(iv) speciation in acidic media based on UV-visible and 31P NMR spectroscopies and molecular modeling

Titanium chemistry in aqueous acidic media has been extensively investigated over the last decades. Hydrolyzed species such as Ti(OH)³⁺, TiO²⁺, Ti(OH)₂²⁺ or Ti(OH)₃⁺ have been identified and their equilibria have been studied in nitric and perchloric acid. A predominance of the divalent cations was found for low pH (i.e., pH <2). Nonetheless, recent literature reports the existence of small titanium oxo-clusters in aqueous acidic media for large titanium(iv) concentration (typically., >0.1 mol L⁻¹), as stable precursors for the formation of condensed titanium dioxide. The present paper reconsiders firstly previous knowledge about the speciation of titanium(iv) in non-complexing acidic media by giving evidence for the presence of polynuclear hydrolyzed species, even at very low Ti(iv) concentration (i.e., typically <0.1 mmol L⁻¹). UV-visible absorbance spectra recorded for diluted nitric acid solutions (a model of non-complexing acidic medium) containing titanium(iv) were compared to time-dependent density functional theory (TD-DFT) predicted excitation energies. Experimental and predicted maximal absorbance wavelengths showed significantly improved matches when polynuclear species were considered in TD-DFT calculation. Then, 0.1–12.7 mol L⁻¹ phosphoric acid solutions containing titanium(iv) were studied by means of spectroscopic techniques (UV-visible, NMR) in order to identify qualitatively the presence of titanium(iv) complexes and to link this speciation to the acid concentration. Two different titanium(iv) orthophosphate complexes, potentially polynuclear, were detected, and the presence of free titanium(iv) is also expected for low phosphoric acid concentration (i.e., <0.1 mol L⁻¹). A general complexation scheme for a large range of H₃PO₄ concentration was thus formulated.

A spectroscopic study of titanium(iv) speciation in diluted nitric acid (model of non-complexing medium) and 0.1–12.7 mol L⁻¹ phosphoric acid aqueous solutions. Evidence for the presence of polynuclear species is supported by molecular modeling.     

Effect of morphology on larvicidal activity of chemically synthesized zinc oxide nanoparticles against mosquito vectors

We report the larvicidal effects of four different morphologies of zinc oxide nanoparticles (ZnO NPs) [star-shaped (S), needle-like (N), plate-like (P) and cubical (C)] on larvae of Aedes albopictus and Anopheles vagus; the mosquitoes causing dengue fever and malaria, respectively. The nanoparticles were characterized by several analytical techniques, and their sizes and shapes were determined. Second instar larvae of the two types of mosquitoes were exposed to several concentrations of nanoparticles (25 mg L⁻¹, 50 mg L⁻¹, 75 mg L⁻¹, 100 mg L⁻¹) at 25 ± 2 °C and 84 ± 5% R.H, separately, for each morphology. Larval mortality was reported at 24 h intervals up to 21 days. The resulting LC₅₀ for Aedes albopictus were, respectively, 38.90 mg L⁻¹, 47.53 mg L⁻¹, 68.38 mg L⁻¹, 50.24 mg L⁻¹ for S-, N-, P- and C-shaped nanoparticles. The LC₅₀ of Anopheles vagus is lower (LC₅₀ 4.78 mg L⁻¹, 6.51 mg L⁻¹, 13.64 mg L⁻¹, 10.47 mg L_⁻¹), respectively, for S-, N-, P- and C-shaped nanoparticles indicating that the nanoparticles are more toxic to Anopheles vagus larvae. The highest larvicidal effect was obtained from star-shaped nanoparticles [Aedes albopictus (38.90 mg L⁻¹) on Anopheles vagus (4.78 mg L⁻¹)], and the lowest was shown by the plate-like nanoparticles [Aedes albopictus (68.38 mg L⁻¹), Anopheles vagus (13.64 mg L⁻¹)]. The rate of development of surviving mosquito larvae was retarded when exposed to ZnO nanoparticles suggesting the possibility for these nanoparticles to kill and delay the growth of Aedes albopictus and Anopheles vagus larvae.

We report the larvicidal impacts of four different morphologies of zinc oxide nanoparticles (ZnO NPs) [star-shaped (S), needle-like (N), plate-like (P), and cubical (C)] on mosquito larvae of Aedes albopictus and Anopheles vagus.     

Rapid and selective electrochemical transformation of ammonia to N2 by substoichiometric TiO2-based electrochemical system

In this study, we have developed a continuous-flow electrochemical system towards the rapid and selective conversion of ammonia to N₂, based on a tubular substoichiometric titanium dioxide (Ti₄O₇) anode and a Pd–Cu co-modified Ni foam (Pd–Cu/NF) cathode, both of which are indispensable. Under the action of a suitable anode potential, the Ti₄O₇ anode enables the conversion of Cl⁻ to chloride radicals (Cl˙), which could selectively react with ammonia to produce N₂. The anodic byproducts, e.g. NO₃⁻, were further reduced to N₂ at the Pd–Cu/NF cathode. EPR and scavenger experiments confirmed the dominant role of Cl˙ in ammonia conversion. Complete transformation of 30 mg L⁻¹ ammonia could be obtained over 40 min of continuous operation under optimal conditions. The proposed electrochemical system also exhibits enhanced oxidation kinetics compared to conventional batch systems. This study provides new insights into the rational design of a high-performance electrochemical system to address the challenging issue of ammonia pollution.

A continuous-flow electrochemical system for rapid and selective conversion of ammonia to N₂ was proposed. The system consists of a tubular substoichiometric titanium dioxide (Ti₄O₇) anode and a Pd–Cu co-modified Ni foam (Pd–Cu/NF) cathode.     

Solvothermal synthesis of Nb-doped TiO2 nanoparticles with enhanced sonodynamic effects for destroying tumors

Titania (TiO₂) nanomaterials have been proved to be biocompatible sonosensitizers for sonodynamic therapy (SDT) of various cancer cells, while they suffer from weak sonodynamic effects due to fast combination of excited carriers. In this work, to improve the therapeutic efficiency, we prepared PEGylated Nb-doped TiO₂ (TiO_2−x:Nb) nanoparticles by a simple solvothermal method and a subsequent surface modification process. The TiO_2−x:Nb nanoparticles exhibited an average size of 11 nm and a polydisperse index of 0.12. The Nb doping had no obvious effect on the phase of TiO₂ matrixes but released electrons to the conduction band of TiO₂, resulting in high concentrations of deficiencies. As a result, the TiO_2−x:Nb nanoparticles exhibited a higher efficiency of singlet oxygen (¹O₂) generation than that of pure TiO₂ nanoparticles upon ultrasound irradiation. Importantly, the TiO_2−x:Nb nanoparticles had high biocompatibility similar to pure TiO₂ nanoparticles, while they could efficiently produce cytotoxic ¹O₂ to destroy cancer cells in vitro in comparison to the partially destroyed cancer cells by pure TiO₂ nanoparticles upon ultrasound irradiation. More importantly, the TiO_2−x:Nb nanoparticles displayed obvious tumor cellular injury in tumor-bearing mice in vivo through high SDT effects. Therefore, the synthesized PEGylated TiO_2−x:Nb nanoparticles in this study exhibited higher therapeutic effects of SDT than that of the pure TiO₂ nanoparticles, and the doping strategy would provide some insights for tuning traditional weak sonosensitizers into efficient ones.

TiO_2−x:Nb nanoparticles displayed obvious tumor cellular injury in tumor-bearing mice in vivo through high SDT effect.     

Different toxicities of nanoscale titanium dioxide particles in the roots and leaves of wheat seedlings

Despite previous studies on exploring the environmental effects of titanium dioxide nanoparticles particle (nTiO₂) on plants, the detailed impacts of nTiO₂ on the antioxidant system and photosynthesis of plants is still not well understood. This study was aimed at investigating the physiological and biochemical responses to nTiO₂ by oxidative damage, Ti bioaccumulation, cell death, and photosynthesis in wheat. The results showed that 5.0 g nTiO₂ L⁻¹ resulted in a significant decrease in plant growth, chlorophyll contents, and photosynthetic activity. However, the obvious accumulation of reactive oxygen species (ROS) and cell death were observed under nTiO₂ treatments in wheat roots and leaves. In addition, the concentrations of Ti in the roots were significantly higher than that in leaves with increased nTiO₂ concentrations. Significant increase in enzyme activities and the levels of ascorbate were found in leaves exposed to 1.0 and 5.0 g nTiO₂ L⁻¹. Furthermore, the level of D1 and PsbS remarkably decreased in wheat leaves at 5.0 g nTiO₂ L⁻¹. However, the strong phosphorylation of photosystem II (PSII) reaction center protein D1 and D2 was observed at 5.0 g nTiO₂ L⁻¹. Altogether, these findings demonstrated that the roots suffered from more severe toxic damage from nTiO₂ than the leaves and wheat plants respond to nTiO₂ through the different physiological and biochemical mechanisms in the roots and leaves.

Despite previous studies on exploring the environmental effects of titanium dioxide nanoparticles particle (nTiO₂) on plants, the detailed impacts of nTiO₂ on the antioxidant system and photosynthesis of plants is still not well understood.     

Zn2+ removal from the aqueous environment using a polydopamine/hydroxyapatite/Fe3O4 magnetic composite under ultrasonic waves

In this study, an easily magnetically recoverable polydopamine (PDA)-modified hydroxyapatite (HAp)/Fe₃O₄ magnetic composite (HAp/Fe₃O₄/PDA) was suitably synthesized to exploit its adsorption capacity to remove Zn²⁺ from aqueous solution, and its structural properties were thoroughly examined using different analytical techniques. The effect of multiple parameters like pH, ultrasonic power, ultrasonic time, adsorbent dose, and initial Zn²⁺ concentration on the adsorption efficiency was assessed using RSM-CCD. According to the acquired results, by increasing the adsorbent quantity, ultrasonic power, ultrasonic time, and pH, the Zn²⁺ adsorption efficiency increased and the interaction between the variables of ultrasonic power/Zn²⁺ concentration, pH/Zn²⁺ concentration, pH/absorbent dose, and ultrasonic time/adsorbent dose has a vital role in the Zn²⁺ adsorption. The uptake process of Zn²⁺ onto PDA/HAp/Fe₃O₄ followed Freundlich and pseudo-second order kinetic models. The maximum capacity of Zn²⁺ adsorption (q_m) obtained by PDA/HAp/Fe₃O₄, HAp/Fe₃O₄, and HAp was determined as 46.37 mg g⁻¹, 40.07 mg g⁻¹, and 37.57 mg g⁻¹, respectively. Due to its good performance and recoverability (ten times), the HAp/Fe₃O₄/PDA magnetic composite can be proposed as a good candidate to eliminate Zn²⁺ ions from a water solution.

A magnetically recoverable polydopamine (PDA)-modified hydroxyapatite (HAp)/Fe₃O₄ magnetic composite (HAp/Fe₃O₄/PDA) was synthesized to exploit its adsorption capacity to remove Zn²⁺ from aqueous solution and the structural properties were examined.     

Black titania nanotubes/spongy graphene nanocomposites for high-performance supercapacitors

A simple method is demonstrated to prepare functionalized spongy graphene/hydrogenated titanium dioxide (FG-HTiO₂) nanocomposites as interconnected, porous 3-dimensional (3D) network crinkly sheets. Such a 3D network structure provides better contact at the electrode/electrolyte interface and facilitates the charge transfer kinetics. The fabricated FG-HTiO₂ was characterized by X-ray diffraction (XRD), FTIR, scanning electron microscopy (FESEM), Raman spectroscopy, thermogravimetric analysis (TGA), UV-Vis absorption spectroscopy, and transmission electron microscopy (TEM). The synthesized materials have been evaluated as supercapacitor materials in 0.5 M H₂SO₄ using cyclic voltammetry (CV) at different potential scan rates, and galvanostatic charge/discharge tests at different current densities. The FG-HTiO₂ electrodes showed a maximum specific capacitance of 401 F g⁻¹ at a scan rate of 1 mV s⁻¹ and exhibited excellent cycling retention of 102% after 1000 cycles at 100 mV s⁻¹. The energy density was 78.66 W h kg⁻¹ with a power density of 466.9 W kg⁻¹ at 0.8 A g⁻¹. The improved supercapacitor performance could be attributed to the spongy graphene structure, adenine functionalization, and hydrogenated titanium dioxide.

A simple method is demonstrated to prepare functionalized spongy graphene/hydrogenated titanium dioxide (FG-HTiO₂) nanocomposites as interconnected, porous 3-dimensional (3D) network crinkly sheets.     

Electrospinning preparation and anti-infrared radiation performance of silica/titanium dioxide composite nanofiber membrane

Silica/titanium dioxide (SiO₂/TiO₂) composite nanofiber membranes with different TiO₂ content were prepared with the technology of electrospinning using ethyl orthosilicate, butyl titanate and polyvinyl pyrrolidone as silicon titanium sources and spinning aids. TGA, XRD, SEM and FT-IR were used to analyze the thermal decomposition process, phase composition, microscopic morphology and infrared properties of the products. The study showed that with the increase of the calcination temperature, the TiO₂ phase gradually changed from amorphous to anatase structure. Above 900 °C, a sample containing rutile TiO₂ with a higher refractive index was obtained. Simultaneously, the continuity of the sample deteriorated, and the mechanical properties deteriorated. The study found that after calcination at 900 °C, the fiber membrane with a TiO₂ content of 12% had the lowest cost and the best overall performance, with tensile strength being 3.09 MPa, and thermal conductivity at 500 °C being 0.0899 W m⁻¹ K⁻¹, which is 20% lower than that of pure SiO₂ fiber membrane. This research provides a reference for the development of high temperature insulation materials with good flexibility.

The silica/titanium dioxide composite fiber membrane is prepared by electrospinning. Based on the shielding effect of rutile titanium dioxide on infrared rays, the fiber membrane has lower infrared transmittance and thermal conductivity.     

Preparation of lysozyme-imprinted nanoparticles on polydopamine-modified titanium dioxide using ionic liquid as a stabilizer

Molecular imprinting of proteins has evolved into an efficient approach for protein recognition and separation. However, maintaining the structural stability of proteins during the preparation process of molecularly imprinted polymers (MIPs) remains challenging. Ionic liquids (ILs), being capable of maintaining the stability of proteins, might enable effective imprinting and accurate recognition of proteins. In this study, lysozyme (Lyz)-imprinted titanium dioxide (TiO₂) nanoparticles, TiO₂@Lyz-MIPs, have been successfully prepared for selective recognition and separation of Lyz. This was achieved by the free radical polymerization of hydroxyethyl acrylate (HEA) and poly(ethylene glycol) dimethacrylate (PEGDMA) on polydopamine (PDA)-modified TiO₂ nanoparticles using an IL, choline dihydrogen phosphate (chol dhp), as the stabilizer of Lyz. It was found that both PDA modification of TiO₂ and the use of chol dhp as stabilizer improved the adsorption capacity of TiO₂@Lyz-MIPs toward Lyz. When the concentration of HEA was 7 mg mL⁻¹, the ratio of monomer to crosslinker was 20 : 1, and the concentration of chol dhp was 12.5 mg mL⁻¹, the highest imprinting factor of 4.40 was achieved. TiO₂@Lyz-MIPs exhibited relatively high adsorption capacity with the maximum adsorption capacity up to 120 mg g⁻¹, which was more than four times higher than that of the non-imprinted polymers (NIPs) counterpart, TiO₂@Lyz-NIPs. The adsorption rate of Lyz by TiO₂@Lyz-MIPs was also much higher than that of TiO₂@Lyz-NIPs. TiO₂@Lyz-MIPs could successfully separate Lyz from diluted egg white, a complex mixture of proteins. Findings from this study indicate that effective recognition cavities toward Lyz were formed on the surface of Lyz-imprinted TiO₂ nanoparticles prepared using IL as the template stabilizer. This approach may facilitate the development of MIPs for efficient protein recognition and separation.

Molecular imprinting of proteins has evolved into an efficient approach for protein recognition and separation.     

Deposition of platinum on boron-doped TiO2/Ti nanotube arrays as an efficient and stable photocatalyst for hydrogen generation from water splitting

An efficient photocatalyst of boron-doped titanium dioxide/titanium nanotube array-supported platinum particles (Pt–B/TiO₂/Ti NTs) was fabricated for photocatalytic water splitting for hydrogen production through a two-step route. First, B/TiO₂/Ti NTs were prepared by anodic oxidation using hydrofluoric acid as electrolyte and boric acid as a B source. Then, Pt particles were deposited on the surface of B/TiO₂/Ti NTs by photo-assisted impregnation reduction. The structure and properties of Pt–B/TiO₂/Ti NTs were characterized by various physical measurements which showed the successful fabrication of Pt–B/TiO₂/Ti NTs. The Pt–B/TiO₂/Ti NTs, with a B-doping content of 15 mmol L⁻¹, showed the highest photocatalytic activity and exhibited a photocatalytic hydrogen-production rate of 384.9 μmol g⁻¹ h⁻¹, which was 9.2-fold higher than that of unmodified TiO₂/Ti NTs (41.7 μmol g⁻¹ h⁻¹). This excellent photocatalytic performance was ascribed mainly to the synergistic effect of Pt and B, which could enhance the photocatalytic activity of TiO₂/Ti NTs.

Pt–B/TiO₂/Ti NTs, prepared by anodic oxidation and photo-deposition methods, showed excellent photocatalytic activity.     

Synthesis of Fe3O4@PVBC–TMT nanoparticles for the efficient removal of heavy metals ions

Core–shell magnetic Fe₃O₄@PVBC–TMT (Fe₃O₄@polyvinylbenzyl chloride–trithiocyanuric acid) nanoparticles containing trithiocyanuric acid groups were fabricated and employed for the fast removal of heavy metals from an aquatic environment. The morphology, structure and properties of Fe₃O₄@PVBC–TMT nanoparticles were characterized by a series of modern analytical tools. The adsorption behavior of the Fe₃O₄@PVBC–TMT nanoparticles for heavy metals ions in aqueous solutions was investigated by batch experiments. The maximum removal capacities of the Fe₃O₄@PVBC–TMT nanoparticles toward Mn²⁺, Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ ions were 127.4, 146.6, 180.5, 311.5, and 528.8 mg g⁻¹, respectively. Importantly, it is found that Pb²⁺ ions can be completely and quickly removed by the Fe₃O₄@PVBC–TMT nanoparticles. The equilibrium was established within 6 min, and the removal efficiencies were found to be 99.9%, 99.8% and 99.5% for Pb²⁺ ions at the initial concentrations of 100 mg L⁻¹, 200 mg L⁻¹ and 300 mg L⁻¹, respectively. It is hoped that the core–shell magnetic Fe₃O₄@PVBC–TMT nanoparticles may find application in wastewater treatment.

Core–shell Fe₃O₄@PVBC–TMT nanoparticles were fabricated and served as a valid magnetic adsorbent for the removal of heavy metals ions.     

Facile organic surfactant removal of various dimensionality nanomaterials using low-temperature photochemical treatment

Deep ultraviolet (DUV)-treatment is an efficient method for the removal of high-energy-barrier polymeric or aliphatic organic ligands from nanomaterials. Regardless of morphology and material, the treatment can be used for nanoparticles, nanowires, and even nanosheets. The high-energy photon irradiation from low-pressure mercury lamps or radio frequency (RF) discharge excimer lamps could enhance the electrical conductivity of various nanomaterial matrixes, such as Ag nanoparticles, Bi₂Se₃ nanosheets, and Ag nanowires, with the aliphatic alkyl chained ligand (oleylamine; OAm) and polymeric ligand (polyvinyl pyrrolidone; PVP) as surfactants. In particular, Ag nanoparticles (AgNPs) that are DUV-treated with polyvinyl pyrrolidone (PVP) for 90 min (50–60 °C) exhibited a sheet resistance of 0.54 Ω □⁻¹, while thermal-treated AgNP with PVP had a sheet resistance of 7.5 kΩ □⁻¹ at 60 °C. The simple photochemical treatment on various dimensionality nanomaterials will be an efficient sintering method for flexible devices and wearable devices with solution-processed nanomaterials.

Deep ultraviolet (DUV)-treatment is an efficient method for the removal of high-energy-barrier polymeric or aliphatic organic ligands from nanomaterials.     

A mitochondrion-targeted dual-site fluorescent probe for the discriminative detection of SO32− and HSO3− in living HepG-2 cells

Sulfur dioxide, known as an environmental pollutant, produced during industrial productions is also a common food additive that is permitted worldwide. In living organisms, sulfur dioxide forms hydrates of sulfite (SO₂·H₂O), bisulfite (HSO₃⁻) and sulfite (SO₃²⁻) under physiological pH conditions; these three exist in a dynamic balance and play a role in maintaining redox balance, further participating in a wide range of physiological and pathological processes. On the basis of the differences in nucleophilicity between SO₃²⁻ and HSO₃⁻, for the first time, we built a mitochondrion-targeted dual-site fluorescent probe (Mito-CDTH-CHO) based on benzopyran for the highly specific detection of SO₃²⁻ and HSO₃⁻ with two diverse emission channels. Mito-CDTH-CHO can discriminatively respond to the levels of HSO₃⁻ and SO₃²⁻. Besides, its advantages of low cytotoxicity, superior biocompatibility and excellent mitochondrial enrichment ability contribute to the detection and observation of the distribution of sulfur dioxide derivatives in living organisms as well as allowing further studies on the physiological functions of sulfur dioxide.

Rational design and sensing mechanism of a dual-site fluorescence probe for HSO₃⁻ and SO₃²⁻.     

Highly selective non-enzymatic electrochemical sensor based on a titanium dioxide nanowire–poly(3-aminophenyl boronic acid)–gold nanoparticle ternary nanocomposite

A novel three component (titanium dioxide nanowire (TiO₂ NW), poly(3-aminophenyl boronic acid) (PAPBA) and gold nanoparticles (Au NPs)) based ternary nanocomposite (TNC) (designated as TiO₂ NW/PAPBA–Au TNC) was prepared by a simple two-stage synthetic approach and utilized for the fabrication of a non-enzymatic (enzyme-free) glucose (NEG) sensor. In stage 2, the PAPBA–Au NC was formed by oxidative polymerization of 3-APBA using HAuCl₄ as oxidant on the surface of pre-synthesized TiO₂ NW via electrospinning (stage 1). The formation of PAPBA–Au NC as the shell on the surface of the TiO₂ NW (core) was confirmed by field emission scanning electron microscopy (FE-SEM). Notably, we obtained a good peak to peak separation, and a high peak current for the redox Fe(CN)₆^3−/4− process indicating excellent electron transfer capability at the glassy carbon electrode (GCE)/TiO₂ NW/PAPBA–Au TNC interface. Also, the fabricated TiO₂ NW/PAPBA–Au TNC provides excellent electrocatalytic activity towards glucose detection in neutral (pH = 7.0) phosphate buffer solution. The detection of glucose was monitored using differential pulse voltammetry. The obtained sensitivity and detection limits are superior to many of the TiO₂ based enzymatic and non-enzymatic glucose sensors reported in the literature. Furthermore, the TiO₂ NW/PAPBA–Au TNC sensor is preferred because of its high selectivity to glucose in the presence of co-existing interfering substances and practical application for monitoring glucose in human blood serum samples.

A highly selective and sensitive enzymeless electrochemical glucose sensor was fabricated based on a novel ternary nanocomposite composed of titanium dioxide nanowire, poly(3-aminophenyl boronic acid) and gold nanoparticles.     

Low temperature scalable synthetic approach enabling high bifunctional electrocatalytic performance of NiCo2S4 and CuCo2S4 thiospinels

Ternary metal sulfides are currently in the spotlight as promising electroactive materials for high-performance energy storage and/or conversion technologies. Extensive research on metal sulfides has indicated that, amongst other factors, the electrochemical properties of the materials are strongly influenced by the synthetic protocol employed. Herein, we report the electrochemical performance of uncapped NiCo₂S₄ and CuCo₂S₄ ternary systems prepared via solventless thermolysis of the respective metal ethyl xanthate precursors at 200 and 300 °C. The structural, morphological and compositional properties of the synthesized nanoparticles were examined by powder X-ray diffraction (p-XRD), transmission electron microscopy (TEM), high-resolution TEM, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) techniques. Electrochemical studies indicate that NiCo₂S₄ nanoparticles synthesized at 300 °C exhibit superior energy storage characteristics with a high specific capacitance of ca. 2650 F g⁻¹ at 1 mV s⁻¹, as compared to CuCo₂S₄ nanoparticles, which showcased a specific capacitance of ca. 1700 F g⁻¹ at the same scan rate. At a current density of 0.5 A g⁻¹, NiCo₂S₄ and CuCo₂S₄ nanoparticles displayed specific capacitances of 1201 and 475 F g⁻¹, respectively. In contrast, CuCo₂S₄ nanoparticles presented a higher electrocatalytic activity with low overpotentials of 269 mV for oxygen evolution reaction (OER), and 224 mV for the hydrogen evolution reaction (HER), at 10 mA cm⁻². The stability of the catalysts was examined for 2000 cycles in which a negligible change in both OER and HER activities was observed.

A scalable solventless approach is employed to prepare NiCo₂S₄ and CuCo₂S₄ with bare surface for enhanced supercapacitance and water splitting. The particles exhibit good energy storage and electrocatalytic activity as well as stability.     

Fabrication of biocompatible magneto-fluorescence nanoparticles as a platform for fluorescent sensor and magnetic hyperthermia applications

Multifunctional nanoparticles with special magnetic and optical properties have been attracting a great deal of attention due to their important applications in the bioanalytical and biomedical fields. In this study, we report the fabrication of biocompatible magneto-fluorescence nanoparticles consisting of carbon dots (CDots) and silica-coated cobalt–manganese nanoferrites (Co_0.5Mn_0.5Fe₂O₄) (CoMnF@Si@CDots) (MagSiCDots) by a facile hydrothermal method. The as-prepared MagSiCDots have a particle size of 100–120 nm and show a negative zeta potential of −35.50 mV at a neutral pH. The fluorescence spectrum of the MagSiCDots nanoparticles consists of sharp excitation at 365 nm and broad blue light emission with a maximum wavelength of 442.5 nm and the MagSiCDots exhibit superparamagnetic behaviour with a saturation magnetization of 11.6 emu g⁻¹. The potential of MagSiCDots as a fluorescent sensor and be used for magnetic hyperthermia applications. It is seen that the fluorescent intensity of a colloidal solution (a hydrogen sulfide (H₂S) solution containing MagSiCDots nanoparticles) has a linear relationship with the H₂S concentration range of 0.2–2 μM. The limit of detection (LOD) of H₂S by our MagSiCDots particles is 0.26 μM and they remain stable for at least 90 min. To test the suitability of the MagSiCDots nanoparticles for use in hyperthermia application, induction heating using an AMF was done. It was observed that these nanoparticles had a specific absorption rate (SAR) of 28.25 W g⁻¹. The in vitro and in vivo cytotoxicity of MagSiCDots were tested on HeLa cells lines. The results show a cell viability of about 85% when exposed to 100 μg mL⁻¹ concentration of the particles. The in vivo cytotoxicity using zebrafish assay also confirmed the non-toxicity and biocompatibility of the nanoparticles to living cells. The reported data demonstrate that by combining CoMnF@Si and fluorescent CDots into a single system, not only nontoxic multifunctional nanomaterials but also multimodal nanoparticles for several applications, such as hazard gas detection and acting as a biocompatible heat source for therapeutic treatment of cancer, are provided.

Multifunctional nanoparticles with special magnetic and optical properties have been attracting a great deal of attention due to their important applications in the bioanalytical and biomedical fields.     

Improved pseudocapacitive charge storage in highly ordered mesoporous TiO2/carbon nanocomposites as high-performance Li-ion hybrid supercapacitor anodes

A Li-ion hybrid supercapacitor (Li-HSCs), an integrated system of a Li-ion battery and a supercapacitor, is an important energy-storage device because of its outstanding energy and power as well as long-term cycle life. In this work, we propose an attractive material (a mesoporous anatase titanium dioxide/carbon hybrid material, m-TiO₂-C) as a rapid and stable Li⁺ storage anode material for Li-HSCs. m-TiO₂-C exhibits high specific capacity (∼198 mA h g⁻¹ at 0.05 A g⁻¹) and promising rate performance (∼90 mA h g⁻¹ at 5 A g⁻¹) with stable cyclability, resulting from the well-designed porous structure with nanocrystalline anatase TiO₂ and conductive carbon. Thereby, it is demonstrated that a Li-HSC system using a m-TiO₂-C anode provides high energy and power (∼63 W h kg⁻¹, and ∼4044 W kg⁻¹).

A mesoporous TiO₂/carbon nanocomposite prepared by block copolymer self-assembly improves pseudocapacitive behavior and achieves high energy/power density Li-ion hybrid supercapacitors.     

A stable TiO2–graphene nanocomposite anode with high rate capability for lithium-ion batteries

A rapid microwave hydrothermal process is adopted for the synthesis of titanium dioxide and reduced graphene oxide nanocomposites as high-performance anode materials for Li-ion batteries. With the assistance of hydrazine hydrate as a reducing agent, graphene oxide was reduced while TiO₂ nanoparticles were grown in situ on the nanosheets to obtain the nanocomposite material. The morphology of the nanocomposite obtained consisted of TiO₂ particles with a size of ∼100 nm, uniformly distributed on the reduced graphene oxide nanosheets. The as-prepared TiO₂–graphene nanocomposite was able to deliver a capacity of 250 mA h g⁻¹ ± 5% at 0.2C for more than 200 cycles with remarkably stable cycle life during the Li⁺ insertion/extraction process. In terms of high rate capability performance, the nanocomposite delivered discharge capacity of ca. 100 mA h g⁻¹ with >99% coulombic efficiency at C-rates of up to 20C. The enhanced electrochemical performance of the material in terms of high rate capability and cycling stability indicates that the as-developed TiO₂–rGO nanocomposites are promising electrode materials for future Li-ion batteries.

A rapid microwave hydrothermal process is adopted for the synthesis of titanium dioxide and reduced graphene oxide nanocomposites as high-performance anode materials for Li-ion batteries.     

A comparison study of MnO2 and Mn2O3 as zinc-ion battery cathodes: an experimental and computational investigation

The high specific capacity, low cost and environmental friendliness make manganese dioxide materials promising cathode materials for zinc-ion batteries (ZIBs). In order to understand the difference between the electrochemical behavior of manganese dioxide materials with different valence states, i.e., Mn(iii) and Mn(iv), we investigated and compared the electrochemical properties of pure MnO₂ and Mn₂O₃ as ZIB cathodes via a combined experimental and computational approach. The MnO₂ electrode showed a higher discharging capacity (270.4 mA h g⁻¹ at 0.1 A g⁻¹) and a superior rate performance (125.7 mA h g⁻¹ at 3 A g⁻¹) than the Mn₂O₃ electrode (188.2 mA h g⁻¹ at 0.1 A g⁻¹ and 87 mA h g⁻¹ at 3 A g⁻¹, respectively). The superior performance of the MnO₂ electrode was ascribed to its higher specific surface area, higher electronic conductivity and lower diffusion barrier of Zn²⁺ compared to the Mn₂O₃ electrode. This study provides a detailed picture of the diversity of manganese dioxide electrodes as ZIB cathodes.

MnO₂ and Mn₂O₃ cathodes for zinc ion batteries were experimentally and computationally explored.