Synthesis, characterization, and cancer cell-selective cytotoxicity of mixed-ligand cobalt(III) complexes of 8-hydroxyquinolines and phenanthroline bases.

Transition metal complexes exhibiting selective toxicity towards a broad range of cancer types are highly desirable as potential anticancer agents. Herein, we report the synthesis, characterization, and cytotoxicity studies of six new mixed-ligand cobalt(III) complexes of general formula [Co(B)2(L)](ClO4)2 (1-6), where B is a N,N-donor phenanthroline base, namely, 1,10-phenanthroline (phen in 1, 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 3, 4), and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 5, 6), and L is the monoanion of 8-hydroxyquinoline (HQ in 1, 3, 5) and 5-chloro-7-iodo-8-hydroxyquinoline (CQ in 2, 4, 6). The X-ray single crystal structures of complexes 1 and 2 as PF6- salts revealed a distorted octahedral CoN5O coordination environment. Complexes demonstrated good stability in an aqueous buffer medium and in the presence of ascorbic acid as a reductant. Cytotoxicity studies using a panel of nine cancer cell lines showed that complex 6, with the dppz and CQ ligands, was significantly toxic against most cancer cell types, yielding IC50 values in the range of 2 to 14 µM. Complexes 1, 3, and 5, containing the HQ ligand, displayed lower toxicity compared to their CQ counterparts. The phenanthroline complexes demonstrated marginal toxicity towards the tested cell lines, while the dpq complexes exhibited moderate toxicity. Interestingly, all complexes demonstrated negligible toxicity towards normal HEK-293 kidney cells (IC50 > 100 µM). The observed cytotoxicity of the complexes correlated well with their lipophilicities (dppz > dpq > phen). The cytotoxicity of complex 6 was comparable to that of the clinical drug cisplatin under similar conditions. Notably, neither the HQ nor the CQ ligands alone demonstrated noticeable toxicity against any of the tested cell lines. The Annexin-V-FITC and DCFDA assays revealed that the cell death mechanism induced by the complexes involved apoptosis, which could be attributed to the metal-assisted generation of reactive oxygen species. Overall, the dppz complex 6, with its remarkable cytotoxicity against a broad range of cancer cells and negligible toxicity toward normal cells, holds significant potential for cancer chemotherapeutic applications.

Experimental and Computational Insights into the Overall Water Splitting Reaction by the Fe-Co-Ni-P Electrocatalyst.

Nonprecious transition-metal phosphides (TMPs) are versatile materials with tunable electronic and structural properties that could be promising as catalysts for energy conversion applications. Despite the facts, TMPs are not explored thoroughly to understand the chemistry behind their rich catalytic properties for the water splitting reaction. Herein, spiky ball-shaped monodispersed TMP nanoparticles composed of Fe, Co, and Ni are developed and used as efficient electrocatalysts for hydrogen and oxygen evolution reaction (HER, OER), and overall water splitting in alkaline medium; and their surface chemistry was explored to understand the reaction mechanism. The optimized Fe0.5CoNi0.5P catalyst shows attractive activities of HER and OER with low overpotentials and Tafel slopes, and with high mass activities, turnover frequencies, and exchange current densities. When applied to overall water splitting, the electrolyzer Fe0.5CoNi0.5P||Fe0.5CoNi0.5P cell can reach a 10 mA cm-2 current density at cell voltages of only 1.52 and 1.56 V in 1.0 M and 30 wt % KOH, respectively, much lower than those of commercial IrO2||Pt/C. The optimized electrolyzer with sizable numbers of chemically active sites exhibits superior durability up to 70 h and 5000 cycles in 1.0 M KOH and can attain a current density as high as 1000 mA cm-2, showing a class of efficient bifunctional electrocatalysis. Experimental and density functional theory-based mechanistic analyses reveal that surface reconstruction takes place in the presence of KOH to form the TMP precatalyst, which results in high coverage of oxygen active species for the OER with a low apparent activation energy (Ea) for conversion of *OOH to O2. These also evidenced the thermoneutral adsorption of H* for the efficient HER half-reaction.

Nanostructured mixed transition metal oxide spinels for supercapacitor applications.

There have been numerous applications of supercapacitors in day-to-day life. Along with batteries and fuel cells, supercapacitors play an essential role in supplementary electrochemical energy storage technologies. They are used as power sources in portable electronics, automobiles, power backup, medical equipment, etc. Among various working electrode materials explored for supercapacitors, nanostructured transition metal oxides containing mixed metals are highly specific and special, because of their stability, variable oxidation states of the constituted metal ions, possibility to tune the mixed metal combinations, and existence of new battery types and extrinsic pseudocapacitance. This review presents the key features and recent developments in the direction of synthesis and electrochemical energy storage behavior of some of the recent morphology-oriented transition metal oxide and mixed transition metal oxide nanoparticles. We also targeted the studies on a few of the recently developed flexible and bendable supercapacitor devices based on these mixed transition metal oxides.

A Superior and Stable Electrocatalytic Oxygen Evolution Reaction by One-Dimensional FeCoP Colloidal Nanostructures.

Transition metal phosphides (TMPs) are expected to be excellent electrocatalysts for oxygen evolution reaction (OER) because of their high stability, highly conducting metalloid nature, highly abundant constituting elements, and the ability to act as a precatalyst due to in situ surface-formed oxy-hydroxide species. Herein, a "one-pot" colloidal approach has been used to develop a rod-shaped one-dimensional non-noble metal FeCoP electrocatalyst, which exhibits an excellent OER activity with an exceptionally high current density of 950 mA cm-2, a turnover frequency value of 7.43 s-1, and a low Tafel slope value of 54 mV dec-1. The FeCoP electrocatalyst affords OER ultralow overpotentials of 230 and 260 mV at current densities of 50 and 100 mA cm-2, respectively, in 1.0 M KOH, and demonstrates a superior catalytic stability of 10,000 cycles and durability up to 60 h at 50 mA cm-2. An insight into the superior and stable electrocatalytic OER performance by the FeCoP nanorods is obtained by extensive X-ray photoelectron spectroscopy, X-ray diffraction, Raman and infrared spectroscopy, and cyclic voltammetry analyses for a mechanistic study. This reveals that a high number of electrocatalytically active sites enhance the oxygen evolution and kinetics by offering metal ion sites for utilitarian in situ surface formation and adsorption of *O, *OH, and *OOH reactive species for OER catalysis.

Superbending (0-180°) and High-Voltage Operating Metal-Oxide-Based Flexible Supercapacitor.

Among various energy storage devices, flexible supercapacitors having high mechanical stability with extreme bending and foldable features are highly attractive for a large number of emerging portable lightweight consumer devices. Here, we report the fabrication of such a superflexible supercapacitor by using novel octahedron-shaped NiCo2O4 nanoparticles as the electrode material for the first time. A new, low-cost hydrothermal method was used to synthesize 50-60 nm monodispersed perfect octahedron nanoparticles without any structural deformation. An all-solid-state symmetric flexible supercapacitor was fabricated by sandwiching the octahedron nanoparticles and [EMIM][BF4] ionic liquid electrolyte between two sheets of newly developed superflexible current collector substrate. The calculated specific capacity and specific capacitance values are found to be 97.9 mAh g-1 and 117.3 F g-1, respectively, at 0.625 A g-1 current density and 3.0 V applied potential. It also offered a high energy density value of 33.54 Wh kg-1 and 10 000 measured cycling stability. The supercapacitor is so flexible that it can be bent or fold up to 180° without any mechanical deformation, and the measured capacitance and energy and power densities remain almost constant at any angle of twisting. For instance, calculated values of capacitances obtained by bending the cell at angles of 180, 150, 135, 90, and 45° are found to be 62, 63.3, 63.73, 64, and 66 F g-1 respectively, in comparison to 67 F g-1 for a nonbending or flat (0°) cell. A faster ion switching between electrode/electrolyte interface, [EMIM][BF4] electrolyte, and octahedron shape of the nanoparticle electrode material is found to be responsible for the outstanding charge storage behavior.

Novel mitochondria targeted copper(ii) complexes of ferrocenyl terpyridine and anticancer active 8-hydroxyquinolines showing remarkable cytotoxicity, DNA and protein binding affinity.

Metal complexes with organelle specificity and potent but selective cytotoxicity are highly desirable. In this work, we report the synthesis, characterization and cytotoxicity of six novel copper(ii) complexes of the formula [Cu(R-tpy)(N-O)]NO3 (1-6), where R-tpy is 4'-phenyl-2,2':6',2''-terpyridine (Ph-tpy; 1-3) or 4'-ferrocenyl-2,2':6',2''-terpyridine (Fc-tpy; 4-6), N-O is the anion of 8-hydroxyquinoline (HQ in 1, 4), 5-chloro-7-iodo-8-hydroxyquinoline (CQ in 2, 5) or 5-nitro-8-hydroxyquinoline (NQ in 3, 6). The complex [Cu(Fc-tpy)2](ClO4)2 (7) has also been prepared as a control and structurally characterized. The optimized geometries and the frontier orbitals of the complexes have been obtained from DFT calculations. The ferrocenyl appended complexes having the anticancer active CQ (in 5) and NQ (in 6) ligands show remarkable cytotoxicity, giving the respective IC50 values of 0.75 µM and 0.52 µM in HeLa and 1.3 µM and 2.6 µM in MCF-7 cancer cells. The phenyl appended complexes 2 and 3 are less active than their ferrocenyl analogues in both the cells while the complexes of HQ (in 1, 4) are the least active. Interestingly, complexes 4-6 are significantly less toxic to MCF-10A normal cells. The DCFDA, annexin-V-FITC and propidium iodide nuclear staining assays reveal an apoptotic mechanism of cell death which is attributable to the metal-assisted generation of reactive oxygen species. Imaging experiments on HeLa cells reveals that complex 5 accumulates primarily inside the mitochondria. The complexes bind to calf thymus DNA with moderate affinity giving Kb values in the range of 6.3 × 104-7.4 × 104 M-1 and to HSA protein with significant affinity giving KHSA values in the range of 8.6 × 104-1.3 × 105 M-1. Their affinity for DNA suggests that mitochondrial DNA could be the target while their affinity for HSA suggests that they could be transported by HSA in the blood. This work is the first report to show that the ferrocenyl appended copper(ii) complexes of hydroxyquinoline ligands are remarkably cytotoxic to cancer cells but significantly less toxic to normal cells.

Development of SnS2/RGO nanosheet composite for cost-effective aqueous hybrid supercapacitors.

The development of low cost supercapacitor cells with unique capacitive properties is essential for many domestic and industrial purposes. Here we report the first ever application of SnS2-reduced graphene oxide (SnS2/RGO) layered nanocomposite as a superior electrode material for symmetric aqueous hybrid supercapacitors. We synthesized SnS2/RGO nanocomposite comprised of nanosheets of SnS2 and graphene oxide via a one-pot hydrothermal approach. in situ as-synthesized SnS2/RGO is devised for the first time to give high specific capacitance 500 Fg-1, energy density 16.67 Wh kg-1 and power density 488 W kg-1. The cell retains 95% charge/discharge cycle stability up to 1000 cycles. In-short, the SnS2/RGO nanosheet composite presented is a novel and advanced material for application in high stability moderate value hybrid supercapacitors. All the currently available surveys in literature state the potential applicability of SnS2 as the anode material for reversible lithium/sodium ion batteries (LIBs/NIBs) but there is a lack of equivalent studies on electrochemical capacitors. We filled up this knowledge gap by the use of the same material in a cost-effective, highly active hybrid supercapacitor application by utilizing its pseudocapacitance property combined with the layered capacitance property of graphene sheets.

Photoinduced ultrafast charge separation in colloidal 2-dimensional CdSe/CdS-Au hybrid nanoplatelets and corresponding application in photocatalysis.

Multicomponent hybrid nanocrystals (HNC) consisting of a semiconductor and metallic domains are an important class of nanostructured materials demonstrating useful applications and interesting basic knowledge. In this scenario, Au nanoparticle (NP) islands of ∼2 nm have been grown on unique two dimensional (2D) CdSe/CdS core@shell hexagonal nanoheteroplatelets of 20 nm diameter to form unprecedented 2D CdSe/CdS-Au HNCs and detailed optical characterization has been carried out to determine the dimensionality based electron transfer dynamics on the ultrafast scale. Steady state optical absorption studies show that upon growing Au NPs onto the 2D nanoplates, a new band appears in the red region of the spectra (500-800 nm), which suggests a strong interaction between the exciton of the core-shell and the plasmon of the metal NPs. Fluorescence studies showed the quenching of emission of the semiconductor domains upon the growth of the metallic domains. Detailed optical and TRPL studies suggested efficient charge transfer from the 2D CdSe/CdS to the Au domains, irrespective of excitation wavelength. Femtosecond transient absorption studies suggest that the electron transfer from the 2D hybrid nanocrystals to the metal domain is on an ultrafast time scale (∼800 fs). No evidence is observed for charge transfer from the 2 nm Au domains to the semiconductor seeds. The broad absorption in the visible region of the hybrid nanocrystals and the ultrafast charge transfer facilitates very efficient photo-catalytic reactions under direct sun light, as a case study.

Exploration of magnetically separable Ag@AgxNiy core/graded-alloy-shell nanostructures.

We report novel bimetallic Ag@AgxNiy core@graded-alloy-shell nanoparticles (CGAS NPs), i.e. single Ag core NPs shelled by an AgxNiy graded alloy and stabilized by the CTAB surfactant employing a novel synthesis method. These Ag@AgxNiy CGAS NPs demonstrated superior catalytic performance in the synthesis of biologically active 3-amino alkylated indoles under green conditions.

Tandem Photocatalysis of Graphene-Stacked SnS2 Nanodiscs and Nanosheets with Efficient Carrier Separation.

Being an optical semiconductor, tin disulfide (SnS2) attracts increasing interest in the fields of heterogeneous photocatalysis and photovoltaics. However, support from a graphene sheet in the form of a nanocomposite is expected to increase the stability and effectiveness of a SnS2 material in potential applications. We report here novel nanocomposites of graphene-oxide-stacked hexagonal-shaped pristine SnS2 nanodiscs (NDs of two different sizes) and nanosheets synthesized using an in situ one-pot hydrothermal synthesis process and the application of the nanocomposite as an efficient heterogeneous photocatalyst. The as-synthesized morphology-oriented nanoparticles and nanocomposites were comprehensively characterized, and finally, excellent photocatalytic activity of reduced graphene oxide/SnS2 nanocomposites under visible-light irradiation was analyzed using UV-vis spectroscopy, high-performance liquid chromatography, and gas chromatography. While precisely manipulating the nanocomposite formation, we observed efficient visible-light-driven photocatalytic application of graphene-stacked SnS2 NDs in the quantitative synthesis of aniline (99.9% yield, absolute selectivity) from nitrobenzene (>99.9% conversion), in the reduction of toxic Cr(VI) to nontoxic Cr(III), and in the degradation of mutagenic organic dyes. A possible synergetic electrical and chemical coupling leads to effective carrier separation in the semiconductor and charge transport in the nanocomposite, which finally gives rise to efficient tandem photocatalysis reactions.

Multiply twinned AgNi alloy nanoparticles as highly active catalyst for multiple reduction and degradation reactions.

Size dependent surface characteristics of nanoparticles lead to use of these nanomaterials in many technologically important fields, including the field of catalysis. Here Ag(1-x)Ni(x) bimetallic alloy nanoparticles have been developed having a 5-fold twinned morphology, which could be considered as an important alloy because of their excellent and unique catalytic and magnetic properties. Alloying between Ag and Ni atoms on a nanoscale has been confirmed with detailed X-ray diffraction, high resolution transmission electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and magnetization measurements. Although introduced for the first time as a catalyst due to having high active surface sites, the as-synthesized nanoparticles showed one of the best multiple catalytic activity in the industrially important (electro)-catalytic reduction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) to corresponding amines with noticeable reduced reaction time and increased rate constant without the use of any large area support. Additionally the same catalyst showed enhanced catalytic activity in degradation of environment polluting dye molecules. The highest ever activity parameter we report here for Ag0.6Ni0.4 composition is 156 s(-1)g(-1) with an apparent rate constant of 31.1 × 10(-3) s(-1) in a 4-NP reduction reaction where the amount of catalyst used was 0.2 mg and the time taken for complete conversion of 4-NP to 4-aminophenol was 60 s. Similarly, an incredible reaction rate constant (115 s(-1)) and activity parameter (576.6 s(-1)g(-1)) were observed for the catalytic degradation of methyl orange dye where 15 s is the maximum time for complete degradation of the dye molecules. The high catalytic performance of present AgNi alloy NPs over the other catalysts has been attributed to size, structural (twinned defect) and electronic effects. This study may lead to use of these bimetallic nanostructures with excellent recyclable catalytic efficiency in many more applications.

New synthesis of two-dimensional CdSe/CdS core@shell dot-in-hexagonal platelet nanoheterostructures with interesting optical properties.

A new strategy for the synthesis of fluorescent monodispersed 2-dimensional (2D) CdSe/CdS core/shell hexagonal platelet nanocrystals has been demonstrated. Because of the stronger affinity of the -NH2 group of oleylamine to the (0001Se) facet comprising three dangling bonds in CdSe seeds, oleylamine acts as the sole surfactant responsible for hindering the growth of the CdS shell in the 0001 and 0001[combining macron] facets and for helping the shell growth anisotropically in the 〈100〉 direction. The as-synthesized products were thoroughly characterized using XRD, TEM/HRTEM, HAADF and STEM for determining the crystal structure, growth mechanism and the position of the seed inside a core/shell nanocrystal. Optical absorption, PL, PLE and TRPL studies revealed efficient photoexcitation and the possibility of polarized emission from 2D core/shell nanocrystals.

Morphology controlled synthesis of nanoporous Co3O4 nanostructures and their charge storage characteristics in supercapacitors.

Cubic spinel Co3O4 nanoparticles with spherical (0D) and hexagonal platelet (2D) morphologies were synthesized using a simple solvothermal method by tuning the reaction time. XRD and HRTEM analyses revealed pure phase with growth of Co3O4 particles along [111] and [110] directions. UV-vis studies showed two clear optical absorption peaks corresponding to two optical band gaps in the range of 400-500 nm and 700-800 nm, respectively, related to the ligand to metal charge transfer events (O(2-) → Co(2+,3+)). Under the electrochemical study in two electrode assembly system (Co3O4/KOH/Co3O4) without adding any large area support or a conductive filler, the hexagonal platelet Co3O4 particles exhibited comparatively better characteristics with high specific capacitance (476 F g(-1)), energy density 42.3 Wh kg(-1) and power density 1.56 kW kg(-1) at current density of 0.5 Ag(-1), that suited for potential applications in supercapacitors. The observed better electrochemical properties of the nanoporous Co3O4 particles is attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.

Development and properties of surfactant-free water-dispersible Cu2ZnSnS4 nanocrystals: a material for low-cost photovoltaics.

A simple, yet novel hydrothermal method has been developed to synthesize surfactant-free Cu2ZnSnS4 nanocrystal ink in water. The environmentally friendly, 2-4 nm ultrafine particles are stable in water for several weeks. Detailed X-ray diffraction (XRD) and high-resolution transmission electron microscopy revealed the formation of single-crystalline-kesterite-phase Cu2ZnSnS4. Elemental mapping by scanning electron microscopy/energy dispersive spectrometry corroborated the presence of all four elements in a stoichiometric ratio with minor sulfur deficiency. Finally, Raman spectroscopy ruled out the possible presence of impurities of ZnS, Cu2SnS3, SnS, SnS2, Cu(2-x)S, or Sn2S3, which often interfere with the XRD and optical spectra of Cu2ZnSnS4. X-ray photoelectron spectroscopic studies of the as-synthesized samples confirmed that the oxidation states of the four elements match those of the bulk sample. Optical absorption analyses of thin film and solution samples showed high absorption efficiency (>10(4) cm(-1)) across the visible and near-infrared spectral regions and a band gap E(g) of 1.75 eV for the as-synthesized sample. A non-ohmic asymmetric rectifying response was observed in the I-V measurement at room temperature. The nonlinearity was more pronounced for this p-type semiconductor when the resistance was measured against temperature in the range 180-400 K, which was detected in the hot-point probe measurement.

Octapod-shaped colloidal nanocrystals of cadmium chalcogenides via "one-pot" cation exchange and seeded growth.

The growth behavior of cadmium chalcogenides (CdE = CdS, CdSe, and CdTe) on sphalerite Cu(2-x)Se nanocrystals (size range 10-15 nm) is studied. Due to the capability of Cu(2-x)Se to undergo a fast and quantitative cation exchange reaction in the presence of excessive Cd(2+) ions, no Cu(2-x)Se/CdE heterostructures are obtained and instead branched CdSe/CdE nanocrystals are built which consist of a sphalerite CdSe core and wurtzite CdE arms. While CdTe growth yields multiarmed structures with overall tetrahedral symmetry, CdS and CdSe arm growth leads to octapod-shaped nanocrystals. These results differ significantly from literature findings about the growth of CdE on sphalerite CdSe particles, which until now had always yielded tetrapod-shaped nanocrystals.

Phosphine-free synthesis of p-type copper(I) selenide nanocrystals in hot coordinating solvents.

We report a phosphine-free synthesis of p-type copper(I) selenide nanocrystals by a colloidal approach in a mixture of oleylamine and 1-octadecene. The nanocrystals had a cuboctahedral shape and cubic berzelianite phase. Films of these nonstoichiometric copper-deficient Cu(2-x)Se nanocrystals were highly conductive and showed high absorption coefficient in the near-infrared region. These nanocrystals could be used as hole-injection layers in optoelectronic devices.

Fluorescent asymmetrically cobalt-tipped CdSe@CdS core@shell nanorod heterostructures exhibiting room-temperature ferromagnetic behavior.

A colloidal two-step seeded-growth approach has been devised to selectively synthesize three-component magnetic/semiconductor hybrid nanocrystals (HNCs) with a matchstick-like profile and tunable geometric parameters. The newly developed heterostructures individually comprise a single metallic Co head connected to either apexes of one rod-shaped section made of a CdSe core eccentrically embedded in a CdS shell. The specific topological arrangement realized arises from the peculiar anisotropic reactivity of the noncentrosymmetric CdSe@CdS core@shell nanorods that have been used as substrates to seed heterogeneous nucleation of Co in a surfactant-free environment from an organometallic precursor. The HNCs retain appreciable fluorescent emission in spite of photoexcited charge transfer from the semiconductor to the metal domain and exhibit unusual ferromagnetic-like behavior at room temperature.

Bioconjugation of rod-shaped fluorescent nanocrystals for efficient targeted cell labeling.

In the present work, we report a three-step approach for the functionalization of CdSe/CdS core/shell and CdSe/CdS/ZnS double-shell quantum rods (QRs) with either biotin or folic acid. We carried out an in vitro study on cultured cells and fixed tissue sections in which the biofunctionalized QRs were compared with the more traditional CdSe/ZnS quantum dots (QDs), which were also functionalized with either biotin or folic acid. The QR and the QD samples exhibited the same specificity toward the targeting cells. In addition, due to the enhanced photoluminescence of the QRs with respect to QDs, a lower amount of rods was required to image cells. In immuno-localization experiments on rat brain tissue sections, biotin-functionalized QRs have shown the typical protein localization patterns expected both for neuronal enolase NSE and actin, confirming the specificity of the interaction of QRs with avidin, and the feasibility of these materials as fluorescent probes in tissue staining. In this specific targeting study, we could assess via the MTT test, a cell viability assay, the lower toxicity of the CdSe/CdS/ZnS QRs with respect to CdSe/CdS QRs.

CdSe/CdS/ZnS double shell nanorods with high photoluminescence efficiency and their exploitation as biolabeling probes.

We report the synthesis, the structural and optical characterization of CdSe/CdS/ZnS "double shell" nanorods and their exploitation in cell labeling experiments. To synthesize such nanorods, first "dot-in-a-rod" CdSe(dot)/CdS(rod) core/shell nanocrystals were prepared. Then a ZnS shell was grown epitaxially over these CdSe/CdS nanorods, which led to a fluorescence quantum yield of the final core-shell-shell nanorods that could be as high as 75%. The quantum efficiency was correlated with the aspect ratio of the nanorods and with the thickness of the ZnS shell around the starting CdSe/CdS rods, which varied from 1 to 4 monolayers (as supported by a combination of X-ray diffraction, elemental analysis with inductively coupled plasma atomic emission spectroscopy and high resolution transmission electron microscopy analysis). Pump-probe and time-resolved photoluminescence measurements confirmed the reduction of trapping at CdS surface due to the presence of the ZnS shell, which resulted in more efficient photoluminescence. These double shell nanorods have potential applications as fluorescent biological labels, as we found that they are brighter in cell imaging as compared to the starting CdSe/CdS nanorods and to the CdSe/ZnS quantum dots, therefore a lower amount of material is required to label the cells. Concerning their cytotoxicity, according to the MTT assay, the double shell nanorods were less toxic than the starting core/shell nanorods and than the CdSe/ZnS quantum dots, although the latter still exhibited a lower intracellular toxicity than both nanorod samples.

Superparamagnetic nanocrystalline ZnFe2O4 with a very high Curie temperature.

Studies on the magnetic properties of nanocrystalline ZnFe2O4 synthesized by an autocombustion method are reported. Superparamagnetic behavior is observed for the nanocrystalline materials with particle sizes of 8 nm and 17 nm, with superparamagnetic blocking temperatures of 65 K and 75 K, respectively. Magnetic hysteresis with very large coercivities of 533 Oe and 325 Oe, respectively, are observed at 12 K. Studies on the temperature variation of the magnetization above room temperature indicate that the Curie temperature is as high as approximately 800 K when compared to the paramagnetic nature of bulk zinc ferrite at room temperature.