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Fabricating multifunctional theranostic nanoparticles is highly pursued but still challenging for effective cancer treatment. Herein is reported a new theranostic nanoagent as both an MRI and targeted chemo/photothermal therapeutic agent. Prussian blue nanoparticles (PB) were first decorated with polydopamine (PDA), then conjugated with polyethylene glycol (PEG) and folic acid (FA), and finally loaded with doxorubicin (DOX) (denoted as PB@PDA@PEG-FA-DOX). The nanoagent was estimated to have an average size of 40 nm with a DOX-loading capacity of 36%, photothermal conversion efficiency of 45.7% and a transverse relaxation rate of 0.366 mM−1 s−1. In vitro release investigations showed a dual-responsive release by a mild acid and near-infrared (NIR) laser irradiation. PB@PDA@PEG-FA illustrated negligible cytotoxicity against the HL-7702 cell line and 38.2% cell viability under NIR against the HeLa cell line. PB@PDA@PEG-FA-DOX exhibited 45.2% cell viability. In contrast, the cell viability of PB@PDA@PEG-FA-DOX was dramatically decreased to 18.4% under NIR. Exclusive of folic acid, PB@PDA@PEG-DOX demonstrated 40.5% cell viability. These results demonstrated the potential of the nanoagent for integrated photothermal therapy (PTT) and chemotherapy, also embracing the FA targeting effect. In vivo MRI confirmed the effective nanoparticle accumulation, while infrared thermal images revealed the dramatically increased temperature under NIR at a tumor site. In vivo combination treatment-induced tumors were nearly completely destroyed without significant body weight loss after 14 days. H&E and Ki67 staining indicated remarkable necrosis and weak cell proliferation in the tumor area. Histologic examination revealed a lower toxicity in the vital organs. Therefore, this combination of chemo/photothermal therapy could provide an efficient route for cancer treatment.

Structural dynamics and changes in electronic structures driven by photoexcited carriers are critical issues in both semiconducting and optoelectronic nanodevices. Herein, a phase diagram for the transient states and relevant dynamic processes in multiwalled boron nitride nanotubes (BNNTs) has been extensively studied for a full reversible cycle after a fs-laser excitation in ultrafast TEMs, and the significant structural features and evolution of electronic natures have been investigated using pulsed electron diffraction and femtosecond-resolved electron energy-loss spectroscopy (EELS). It is revealed that nonthermal anisotropic alterations of the lattice apparently precede the phonon-driven thermal transients along the radial and axial directions. Ab initio calculations support these findings and show that electrons excited from the π to π* orbitals in the BN nanotubes weaken the intralayer bonds while strengthening the interlayer bonds along the radial direction. Importantly, time-resolved EELS measurements show contraction of the energy bandgap after fs-laser excitation associated with nonthermal structural transients. This fact verifies that laser-induced bandgap renormalization in semiconductors can essentially be correlated with both the rapid processes of excited carriers and nonthermal lattice evolution.

A simple approach for constructing theranostic nanobeads is developed by using doxorubicin as a phase transfer agent to solubilize small iron oxide nanoclusters. The nanobeads can be specifically internalized into cancer cells with the guidance of an external magnetic field, resulting in good MRI and chemotherapy.

Theranostic nanoprobes integrated with dual-modal imaging and therapeutic functions, such as photodynamic therapy (PDT), have exhibited significant potency in cancer treatments due to their high imaging accuracy and non-invasive advantages for cancer elimination. However, biocompatibility and highly efficient accumulation of these nanoprobes in tumor are still unsatisfactory for clinical application. In this study, a photosensitizer -loaded magnetic nanobead with surface further coated with a layer of cancer cell membrane (SSAP-Ce6@CCM) was designed to improve the biocompatibility and cellular uptake and ultimately achieve enhanced MR/NIR fluorescence imaging and PDT efficacy. Compared with similar nanobeads without CCM coating, SSAP-Ce6@CCM showed significantly enhanced cellular uptake, as evidenced by Prussian blue staining, confocal laser scanning microscopy (CLSM) and flow cytometric analysis. Consequently, SSAP-Ce6@CCM displayed a more distinct MR/NIR imaging ability and more obvious photo-cytotoxicity towards cancer cells under 670 nm laser irradiation. Furthermore, the enhanced PDT effect benefited from the surface coating of cancer cell membrane was demonstrated in SMMC-7721 tumor-bearing mice through tumor growth observation and tumor tissue pathological examination. Therefore, this CCM-disguised nanobead that integrated the abilities of MR/NIR fluorescence dual-modal imaging and photodynamic therapy might be a promising theranostic platform for tumor treatment.

Tumor microenvironment activated nanodevices have remarkable superiority to enhance therapeutic efficacy and minimize side effects, but their practical applications are dramatically reduced by the low abundance and heterogeneous distribution of specific stimuli at the tumor site. Herein, programmable vesicular nanodevices based on the triblock copolymer containing poly(ethylene glycol) (PEG) and poly(caprolactone) (PCL) with peroxalate esters (PO) as hydrogen peroxide-responsive linkage (PEG-PO-PCL-PO-PEG), are developed for co-delivery of hypoxia-activated prodrug (AQ4N) and glucose oxidase (GOD). The obtained nanodevices (PAG) can be activated by the high level of H2 O2 in tumor microenvironment to improve the permeability of membranes for glucose entrance. Afterward, the oxidation of glucose catalyzed by GOD produces amplified H2 O2 amounts which in turn induce complete destruction of PAG for fast release of AQ4N and GOD. Ultimately, the PAG can exert programmable therapeutic effects from the following aspects: 1) starvation therapy by cutting off the energy supply from glucose through GOD catalysis; 2) oxidative cytotoxicity after H2 O2 amplification; 3) chemotherapy of AQ4N activated by the intensified tumor hypoxia microenvironment after oxygen consumption. The stimuli amplification, controlled drug release, synergistic therapy, and corresponding mechanisms of PAG are demonstrated. Therefore, the presented work could provide significant new insights for cancer treatment.

In situ heating transmission electron microscopy observations clearly reveal remarkable interlayer expansion and inner-layer inward contraction in multi-walled boron nitride nanotubes (BNNTs) as the specimen temperature increases. We interpreted the observed inward contraction as being due to the presence of the strong constraints of the outer layers on radial expansion in the tubular structure upon in situ heating. The increase in specimen temperature upon heating can create pressure and stress toward the tubular center, which drive the lattice motion and yield inner diameter contraction for the multi-walled BNNTs. Using a simple model involving a wave-like pattern of layer-wise distortion, we discuss these peculiar structural alterations and the anisotropic thermal expansion properties of the tubular structures. Moreover, our in situ atomic images also reveal Russian-doll-type BN nanotubes, which show anisotropic thermal expansion behaviors.

Epitaxial bilayered thin films of BaxSr1−xTiO3 (BSTO, x = 0.1 and 0.5)/YBa2Cu3O7−δ (YBCO), with different YBCO film thicknesses, have been grown in situ by pulsed-laser deposition on 1.2° vicinal LaAlO3 substrates. The critical thickness for the transformation of the growth mode in YBCO between two-dimensional (2D) step flow and three-dimensional island is experimentally confirmed to be around 180 nm. As the YBCO-film thickness increases from 145 to 250 nm, the tremendous degradation of the film quality, due to the growth-mode change in YBCO, leads to drastic deterioration in the dielectric properties of BSTO thin films, with severe decrease in the figure of merit factor from 148 to 10 in Ba0.1Sr0.9TiO3/YBCO (at 77 K and 100 kHz) and from 56 to 6 in Ba0.5Sr0.5TiO3/YBCO (at 300 K and 100 kHz). As a result, the dielectric properties of BSTO thin films could be significantly enhanced by strictly tailoring the growth mode in YBCO as a 2D step flow for this kind of BSTO/YBCO bilayers.

Double-sided Tl2Ba2CaCu2O8 (Tl-2212) thin films have been prepared on lanthanum aluminate (LaAlO3) substrates by a two-step method in which Tl-free amorphous Ba2CaCu2Ox., precursor films were first deposited on the substrates by pulsed laser deposition (PLD) and the subsequent thalliation, crystallization and oriented growth of the superconducting Tl-2212 films were obtained in a long-duration annealing process in argon atmosphere at temperature around 730-750degreesC. The films were characterized by means of x-ray diffraction (XRD), electron simulated x-ray microanalysis in the energy dispersive mode (EDX), scanning electron microscopy (SEM) and transport measurements. The results show that the as-prepared films are predominately single phase, except for the presence of some submicron particles on the film surface. The films show epitaxial growth with c-axis perpendicular to the substrate surface, as confirmed by XRD. The full width at half maximum (FWHM) of the (0012) peak determined from the rocking curves is 0.92degrees and 1.21degrees for the two sides of a double-sided Tl-2212 film, respectively. The zero-resistance transition temperature (T-C0) is 108.8 K for one side and 106.7 K for the other side of the film. The critical current density (J(C)) is in excess of 106 A cm(-2) for both sides of the films.

Electrical and magnetic transitions in Pr1−x Srx MnO3 and Pr1−x Srx Mn0.95Fe0.05O3 ceramic samples with x = 1/4, 3/8, and 1/ 2h ave been investigated. It is proved that 5% Fe doping in the system suppresses electrical conduction and ferromagnetism severely, but favours antiferromagnetism. The existence of spin clusters at temperatures above the ferromagnetic transition TC is demonstrated in the Fe-dopedx = 1/ 2s ample, which is caused by the Fe-doping-induced magnetic inhomogeneity. The transport behaviour above TC in this sample is governed by variable-range hopping of the magnetic polarons. For the Fe-doped x = 1/ 4s ampl e, the insulator-to-metal (I–M) transition drops behind TC by nearly 80 K; accordingly, two magnetoresistance peaks appear. One is around TC ,a nd the other lies just at the I–M transition temperature. The possible underlying mechanism is discussed qualitatively. (Some figures in this article are in colour only in the electronic version)

The irreversibility line of superconductors is most usually established from magnetization curves. However, many low-${T}_{c}$ materials show extremely reversible magnetization curves, while still having a finite critical current. Confirmation of a reversibility line requires other measurements. We have made measurements of dc magnetization, ac susceptibility, and magnetoresistivity as a function of applied field and temperature on Nb alloy samples in order to investigate the irreversibility line in low-${T}_{c}$ superconductors. The results show that there exists an observable field region below the mean-field critical field ${B}_{c2},$ where the magnetization is reversible during a cycle of increasing and decreasing field, which is in agreement with a previous report by Suenaga et al. In addition to dc magnetization, ac susceptibility and magnetoresistivity measurements were also carried out on the same sample as alternative techniques to probe the irreversibility line to determine the best way of distinguishing a genuine thermally activated reversibility from a finite, but low, critical current density. The results showed that the collapse of the dc magnetic hysteresis, the onset of the diamagnetic ac susceptibility (or the peak of the ac loss) and the zero resistance occur at nearly the same field, namely, the irreversibility field ${B}_{\mathrm{irr}}.$ These experimental observations indicate that the irreversibility line is not unique to high-${T}_{c}$ oxides but also exists in conventional superconducting metallic alloys although much closer to ${B}_{c2}.$ However, it is difficult to reconcile these results with measurements on other low-${T}_{c}$ materials which show zero resistance up to the surface critical field ${B}_{c3}.$

Chevrel phase superconductors with upper critical field values of up to 50 T, are candidate materials for the next generation of high field magnets. We have investigated the effect of doping lead-molybdenum-sulphide with the magnetic ion gadolinium to improve the critical parameters and the flux pinning in this material. Samples were prepared at 1500/spl deg/C to ensure the gadolinium was uniformly distributed throughout the material and then sintered using a hot isostatic press operating at a pressure of 2000 atmospheres. Calorimetric measurements have been completed In magnetic fields up to 15 T as a function of temperature. The temperature dependence of the upper critical field of these isotropic Chevrel phase materials are presented. Upper critical field values of more than 60 T have been determined for both doped and undoped samples. The calorimetric data reported here show that material with low levels of gadolinium doping offers the possibility of strong flux pinning and high critical current densities in high magnetic fields. In highly doped materials, the low critical current density and irreversibility fields found are probably due to a reduction in the fundamental properties and not poor grain boundaries.

The structural and transport properties of LaTiO3+beta/2 epitaxial thin films, grown at different oxygen pressures ranging from 6.6 x 10(-4) to 5 Pa, have been investigated. X-ray diffraction peaks of the films shift to lower angles with increasing oxygen pressure, indicative of a variation of the corresponding lattice spacing. All the films show T 2 dependence of resistivity over a large temperature range of similar to 200 K, suggesting a band-filling-induced metallic Fermi-liquid behaviour. Upturns in resistivity have been revealed at low temperatures, which could be ascribed to the Anderson-localization effect caused by the cation vacancies. Furthermore, for the thin films grown at high oxygen pressures of 0.5 and 5 Pa, the dependence of resistivity on temperature shows a maximum at high temperatures. The maximum seems to support the argument that transition between t-orbital ordering and disordering plays an important role in dominating transport properties at high temperatures. Carrier density deduced from Hall coefficient increases with the decrease of oxygen content, and shows strong temperature dependence. From the experimental data, it can be asserted that in the LaTiO3+beta/2 thin films, besides the band filling effect, localization or disorder caused by La and Ti vacancy effects controls the unique transport properties.

A series of Al-doped Mg1-xAlxB2 samples have been fabricated and systematic study on structure and superconducting properties have been carried out for the samples. In addition to a structural transition observed by XRD, TEM micrographs showed the existence of a superstructure of double c-axis lattice constant along the direction perpendicular to the boron honeycomb sheet. In order to investigate the effect of Al doping on flux pinning and critical current properties in MgB2, measurements on the superconducting transition temperature T-c, irreversible field B-irr and critical current density J(c) were performed too, for the samples with the doping levels lower than 0.15 in particular. These experimental observations were discussed in terms of Al doping induced changes in carrier concentration. (C) 2004 Elsevier B.V. All rights reserved.

A two-step transition model describing phase diffusion and switching process in underdamped Josephson junctions is discussed. The model takes into account the phase particle's escape rate out of the potential well and transition rate from phase diffusion to the running state. Using as examples the experimental switching current distributions of two Nb/AlOx/Nb junctions of different sizes fabricated on the same chip, we extract the transition rate, which turns out to follow the predicted Arrhenius law in the thermal regime but is greatly enhanced when macroscopic quantum tunneling becomes the dominant escape mechanism. Our results show the validity of applying the model to obtain the transition rate out of the phase diffusion state into the running state from measured switching current distribution of underdamped Josephson junctions. The temperature and bias-current dependent data provide strong evidence for phase diffusion in both thermal and quantum regimes.

We have prepared material with high content of 110K superconducting phase by a novel two-step synthetic method. The samples have been characterized by both resistive and a.c. magnetic measurements, secondary electron microscopy, EDX micro-analysis and X-ray diffraction. The 110K superconducting phase has been found to be the Bi 2 Sr 2 Ca 2 Cu 3 O y compound with a layered orthorhombic structure, with a=5.42, b=5.44 and c=36.8 Å respectively.

In YBa 2 Cu 3 O 7−x, the more the oxygen content is the higher is the Tc, the smaller is the lattice parameter c and the unit cell volume V. But in LaBa 2 Cu 3 O 7+x the less the oxygen content is, the higher is the Tc, the larger are c and V. These may be due to oxygen content being less than 7.0 in YBa 2 Cu 3 O 7−x and more than 7.0 in LaBa 2 Cu 3 O 7+x. These results give some informations regarding superconducting mechanism and show that the one-dimensional chain plays an important role.

In this paper the current-voltage (I-V) curves of Bi 2 Sr 2 CaCu 2 O y single crystals both along the c direction and in the a-b plane are measured. There is obvious anisotropy in these two directions. Also there is no hysteresis in the I-V curve along the c axis, which is expected when there is weak coupling along the c direction. The normalized critical current density J c (T)/J c (78 K) vs. T relation is also given.

We have prepared 120 K superconductor in Tl-Ba-Ca-Cu oxide system. This 120 K superconductor has been investigated by x-ray diffraction and EDAX micro-analysis. EDAX analysis shows that the composition of this superconductor is very close to TlBa ( Ca 1−x Cu x) CuO y(x−0.3). Most of the x-ray powder diffractions including all the strong ones can be indexed according to a tetragonal structure with a=5.46 Å and c= 36.2 Å which means that the sample is nearly a single phase material.

The critical current density J c has been measured in a series of Chevrel phase Pb 1− x Gd x Mo 6 S 8 ( x = 0, 0.1, 0.2 and 0.3) bulk samples made using a hot isostatic pressing process. Adding Gd markedly increases the critical temperature, and the upper critical field found using resistivity, susceptibility and heat capacity measurements. The grain boundaries are found to be clean when observed using TEM. However, increasing the level of Gd, causes J c and the irreversibility field B irr to decrease dramatically. In particular, J c becomes more field dependent as more Gd is added. The pinning force density for all samples can be described either by a Kramer relation F p = J c × B ∝ b 1 2 (1 − b) 2 or by an exponential relation J c = α ( T )exp[− B / β ( T )], over a wide field and temperature range. This indicates that one mechanism controls J c in all the samples. This study shows that adding Gadolinium improves the intrinsic properties ( T c , B c2 ( T )) and yet simultaneously degrades the extrinsic properties ( J c , B irr ). It is suggested that the Gadolinium acts as an oxygen getter which improves the intrinsic properties of the grains but causes local compositional variations at the grain boundaries which reduces J c .