Therapeutic mesopore construction on 2D Nb2C MXenes for targeted and enhanced chemo-photothermal cancer therapy in NIR-II biowindow.

Two-dimensional (2D) MXenes have emerged as a promising planar theranostic nanoplatform for versatile biomedical applications; but their in vivo behavior and performance has been severely influenced and hindered by a lack of necessary surface chemistry for adequate surface engineering. To solve this critical issue, this work employs versatile sol-gel chemistry for the construction of a unique "therapeutic mesopore" layer onto the surface of 2D niobium carbide (Nb2C) MXene. Methods: The in situ self-assembled mesopore-making agent (cetanecyltrimethylammonium chloride, in this case) was kept within the mesopores for efficient chemotherapy. The abundant surface saline chemistry of mesoporous silica-coated Nb2C MXene was further adopted for stepwise surface engineering including PEGylation and conjugation with cyclic arginine-glycine-aspartic pentapeptide c(RGDyC) for targeted tumor accumulation. Results: 2D Nb2C MXenes were chosen based on their photothermal conversion capability (28.6%) in the near infrared (NIR)-II biowindow (1064 nm) for enhanced photothermal hyperthermia. Systematic in vitro and in vivo assessments demonstrate targeted and enhanced chemotherapy and photothermal hyperthermia of cancer (U87 cancer cell line and corresponding tumor xenograft; inhibition efficiency: 92.37%) in the NIR-II biowindow by these mesopore-coated 2D Nb2C MXenes. Conclusion: This work not only significantly broadens the biomedical applications of 2D Nb2C MXene for enhanced cancer therapy, but also provides an efficient strategy for surface engineering of 2D MXenes to satisfy versatile application requirements.

Propagation characteristics of a focused laser beam in a strontium barium niobate photorefractive crystal under reverse external electric field.

The propagation characteristics of a focused laser beam in a SBN:75 photorefractive crystal strongly depend on the signal-to-background intensity ratio (R=Is/Ib) under reverse external electric field. In the range 20>R>0.05, the laser beam shows enhanced self-defocusing behavior with increasing external electric field, while it shows self-focusing in the range 0.03>R>0.01. Spatial solitons are observed under a suitable reverse external electric field for R=0.025. A theoretical model is proposed to explain the experimental observations, which suggest a new type of soliton formation due to "enhancement" not "screening" of the external electrical field.

Optical temperature sensing based on the near-infrared emissions from Nd³âº/Yb³âº codoped CaWO4.

Under a 980 nm diode laser excitation, the near-infrared (NIR) emissions from Nd3+:4F7/2, 4F5/2, and 4F3/2 states in Nd3+/Yb3+ codoped CaWO4 powder were studied at temperatures ranging from 303 to 873 K. As the temperature increased, the NIR luminescence intensity was significantly enhanced and nearly 190-fold enhancement was achieved at 873 K compared with that at 303 K. By using the fluorescence intensity ratio technique, the thermometry behaviors through the NIR emissions were investigated. The results illustrate that the sensitivity and the accuracy achieved here are much higher than temperature sensors based on other rare earth ion doped materials.

Specific features of the influence of high-energy electron beams on the luminescent properties of undoped and Nb, Fe-doped Al2O3 crystals.

The influence of 10 MeV high-current electron beams accelerated by the M-30 microtron on the luminescent properties of the α-Al2O3, Al2O3:Nb and Al2O3:Fe crystals has been studied. The effect of the long-term phosphorescence at room temperature has been found that can be used to monitor electron and gamma accelerator beams.

PMN-PT single-crystal high-frequency kerfless phased array.

This paper reports the design, fabrication, and characterization of a miniature high-frequency kerfless phased array prepared from a PMN-PT single crystal for forward-looking intravascular or endoscopic imaging applications. After lapping down to around 40 µm, the PMN-PT material was utilized to fabricate 32-element kerfless phased arrays using micromachining techniques. The aperture size of the active area was only 1.0 × 1.0 mm. The measured results showed that the array had a center frequency of 40 MHz, a bandwidth of 34% at -6 dB with a polymer matching layer, and an insertion loss of 20 dB at the center frequency. Phantom images were acquired and compared with simulated images. The results suggest that the feasibility of developing a phased array mounted at the tip of a forward-looking intravascular catheter or endoscope. The fabricated array exhibits much higher sensitivity than PZT ceramic-based arrays and demonstrates that PMN-PT is well suited for this application.

Synthesis, crystal structure and photocatalytic properties of an unprecedented arsenic-disubstituted Lindqvist-type peroxopolyoxoniobate ion: {As2Nb4(O2)4O14H1.5}(4.5-).

An unprecedented arsenic-disubstituted Lindqvist-type peroxopolyoxoniobate Cs2.5Na2{As2Nb4(O2)4O14H1.5}·11H2O has been successfully synthesized and characterized. The photocatalytic activity of the cluster for H2 evolution from water is investigated by irradiating with a 300 W Xe lamp, which shows a certain photocatalytic water splitting activity.

Cell membrane deformation induced by a fibronectin-coated polystyrene microbead in a 200-MHz acoustic trap.

The measurement of cell mechanics is crucial for a better understanding of cellular responses during the progression of certain diseases and for the identification of the cell's nature. Many techniques using optical tweezers, atomic force microscopy, and micro-pipettes have been developed to probe and manipulate cells in the spatial domain. In particular, we recently proposed a two-dimensional acoustic trapping method as an alternative technique for small particle manipulation. Although the proposed method may have advantages over optical tweezers, its applications to cellular mechanics have not yet been vigorously investigated. This study represents an initial attempt to use acoustic tweezers as a tool in the field of cellular mechanics in which cancer cell membrane deformability is studied. A press-focused 193-MHz single-element lithium niobate (LiNbO3) transducer was designed and fabricated to trap a 5-µm polystyrene microbead near the ultrasound beam focus. The microbeads were coated with fibronectin, and trapped before being attached to the surface of a human breast cancer cell (MCF-7). The cell membrane was then stretched by remotely pulling a cell-attached microbead with the acoustic trap. The maximum cell membrane stretched lengths were measured to be 0.15, 0.54, and 1.41 µm at input voltages to the transducer of 6.3, 9.5, and 12.6 Vpp, respectively. The stretched length was found to increase nonlinearly as a function of the voltage input. No significant cytotoxicity was observed to result from the bead or the trapping force on the cell during or after the deformation procedure. Hence, the results convincingly demonstrated the possible application of the acoustic trapping technique as a tool for cell manipulation.

Anisotropy of the acoustic plate modes in ST-quartz and 128°Y-LiNbO(3).

Orientation dependences of the phase velocity vn, coupling coefficient Kn(2), and power flow angle Ψ(n) for zero-order and high-order acoustic modes are calculated numerically in ST-quartz and 128°Y-LiNbO(3) plates with normalized thickness h/λ = 0.1, 0.25, 0.5, 1.0, 1.25, 1.5, and 1.67 (n is the mode order, θ is the angle between propagation direction and the x-axis, h is the thickness, and λ is the wavelength). Results of the calculations are experimentally verified using 128°YLiNbO(3) plates with h/λ = 1.0, 1.67 and θ = 0°, 30°, 60°, 90° as examples.

LiNbO3 coating on concrete surface: a new and environmentally friendly route for artificial photosynthesis.

The addition of a photocatalyst to ordinary building materials such as concrete creates environmentally friendly materials by which air pollution or pollution of the surface can be diminished. The use of LiNbO3 photocatalyst in concrete material would be more beneficial since it can produce artificial photosynthesis in concrete. In these research photoassisted solid-gas phases reduction of carbon dioxide (artificial photosynthesis) was performed using a photocatalyst, LiNbO3, coated on concrete surface under illumination of UV-visible or sunlight and showed that LiNbO3 achieved high conversion of CO2 into products despite the low levels of band-gap light available. The high reaction efficiency of LiNbO3 is explained by its strong remnant polarization (70 µC/cm(2)), allowing a longer lifetime of photoinduced carriers as well as an alternative reaction pathway. Due to the ease of usage and good photocatalytic efficiency, the research work done showed its potential application in pollution prevention.

Effects of the duty ratio on the niobium oxide film deposited by pulsed-DC magnetron sputtering methods.

Niobium oxide (Nb2O5) films were deposited on p-type Si wafers and sodalime glasses at a room temperature using in-line pulsed-DC magnetron sputtering system with various duty ratios. The different duty ratio was obtained by varying the reverse voltage time of pulsed DC power from 0.5 to 2.0 micros at the fixed frequency of 200 kHz. From the structural and optical characteristics of the sputtered NbOx films, it was possible to obtain more uniform and coherent NbOx films in case of the higher reverse voltage time as a result of the cleaning effect on the Nb2O5 target surface. The electrical characteristics from the metal-insulator-semiconductor (MIS) fabricated with the NbOx films shows the leakage currents are influenced by the reverse voltage time and the Schottky barrier diode characteristics.

Preparation and enhanced visible-light photocatalytic activity of graphitic carbon nitride/bismuth niobate heterojunctions.

A series of graphitic carbon nitride/bismuth niobate (g-C3N4/Bi5Nb3O15) heterojunctions with g-C3N4 doping level of 10-90 wt% were prepared by a facile milling-heat treatment method. The phase and chemical structures, surface compositions, electronic and optical properties as well as morphologies of the prepared g-C3N4/Bi5Nb3O15 were well-characterized. Subsequently, the photocatalytic activity and stability of g-C3N4/Bi5Nb3O15 were evaluated by the degradation of aqueous methyl orange (MO) and 4-chlorophenol (4-CP) under the visible-light irradiation. At suitable g-C3N4 doping levels, g-C3N4/Bi5Nb3O15 exhibited enhanced visible-light photocatalytic activity compared with pure g-C3N4 or Bi5Nb3O15. This excellent photocatalytic activity was revealed in terms of the extension of visible-light response and efficient separation and transportation of the photogenerated electrons and holes due to coupling of g-C3N4 and Bi5Nb3O15. Additionally, the active species yielded in the pure g-C3N4- and g-C3N4/Bi5Nb3O15-catalyzed 4-CP photodegradation systems were investigated by the free radical and hole scavenging experiments.

Control of the properties of micro-structured waveguides in lithium niobate crystal.

We study numerically depressed-index cladding, buried, micro-structured optical waveguides that can be formed in a lithium niobate crystal by femtosecond laser writing. We demonstrate to which extent the waveguiding properties can be controlled by the waveguide geometry at the relatively moderate induced refractive index contrasts that are typical of the direct femtosecond inscription.

Observation of a cascaded process in intracavity terahertz optical parametric oscillators based on lithium niobate.

Cascaded difference frequency generation has been observed in intracavity optical parametric oscillators based on bulk lithium niobate and producing nanosecond pulses of terahertz radiation. Two idler waves are generated, namely: the primary idler wave associated with the parametric down conversion process itself; and a secondary idler wave, due to difference frequency generation. Experimental investigations of the frequency, temporal evolution, propagation direction, intensity, phase matching and oscillation threshold of the generated down-converted waves are reported. The overall generation efficiency for the terahertz radiation is enhanced, thereby overcoming the Manley-Rowe limit. Advantages of the present approach over schemes based on periodically poled lithium niobate are identified.

Evaluation of photocatalytic activities of supported catalysts on NaX zeolite or activated charcoal.

This study aimed to evaluate the photocatalytic activity of ZnO and Nb2O5 catalysts, both supported on NaX zeolite and activated charcoal (AC). The synergistic effect between oxide and support and the influence of solution pH (3, 7 and 9) on photocatalytic degradation of reactive blue 5G (C.I. 222) were analyzed. The catalysts Nb2O5/NaX, Nb2O5/AC and ZnO/NaX, ZnO/AC with 5 and 10% (wt%) were prepared by wet impregnation. The results showed that the catalysts exhibit quite different structural and textural properties. The synergic effect between ZnO and NaX support was higher than that with the activated charcoal, showing that these catalysts were more efficient. The most photoactive catalyst was 10% ZnO/NaX which showed 100% discoloration of the dye solution at pH 3, 7 and 9 after 0.5, 5 and 2h of irradiation, respectively. The hydrolytic nature of zeolite favored the formation of surface hydroxyl radicals, which increased the activity of the photocatalyst. Thus, catalysts supported on NaX zeolite are promising for use in photocatalysis.

Investigation of a planar optical waveguide in 2D PPLN using helium implantation technique.

In this work, we report the investigation of a planar waveguide in a 2D periodically-poled lithium niobate (PPLN). The waveguide is fabricated by helium (He(+)) implantation at 2 MeV and a fluence of 1.5 x 10(16) ions/cm(2). Second harmonic generation (SHG) at 532 nm using a Q-switched laser and a CW laser diode at 1064 nm, was measured as a function of angular distribution and temperature. The experimental results show higher gain in SHG conversion efficiency in the waveguide than in the bulk 2D PPLN. In particular, SHGs from 2D reciprocal lattice vectors (RLV) are observed and studied.

Observation of surface dark photovoltaic solitons.

Surface dark solitons in photovoltaic nonlinear media are reported. Taking advantage of diffusion and photovoltaic nonlinearities we demonstrated the surface dark solitons and their behaviors near surface theoretically and experimentally in LiNbO3 crystal. It is very interesting that surface dark soliton is just half of dark soliton in bulk. Another interesting thing is that transverse modulation instability can be perfectly suppressed by surface dark soliton in virtue of surface. In addition, surface waveguides were written successfully utilizing surface dark soliton.

Electro-optically tunable, multi-wavelength optical parametric generators in aperiodically poled lithium niobates.

We report on the design and demonstration of electro-optically tunable, multi-wavelength optical parametric generators (OPGs) based on aperiodically poled lithium niobate (APPLN) crystals. Two methods have been proposed to significantly enhance the electro-optic (EO) tunability of an APPLN OPG constructed by the aperiodic optical superlattice (AOS) technique. This is done by engineering the APPLN domain structure either in the crystal fabrication or in the crystal design process to increase the length or block-number difference of the two opposite-polarity domains used in the structure. Several orders of magnitude enhancement on the EO tuning rate of the APPLN OPGs constructed by the proposed techniques for simultaneous multiple signal wavelength generation over a conventional one has been demonstrated in a near infrared band (1500-1600 nm).

Modulation characteristics of DC Josephson current through Nb tunnel junction by applying external magnetic field in perpendicular direction.

Perpendicular magnetic field dependences of the Josephson current through tunnel junction were first measured. Niobium/aluminum-oxide/niobium (200/5/150 nm in thickness) superconducting tunnel junctions were fabricated by DC-magnetron apparatus with a load-lock chamber. Josephson current Ic through the superconducting junction is usually changed by the external magnetic field in one direction to check the barrier uniformity. To obtain more information of the barrier uniformity, we have changed the external magnetic field in two directions (Hx and Hy: parallel field to the junction plane) parallel to the junction plane. The shape of Ic-Hx curve and Ic-Hy curve were the Fraunhofer pattern in the Ic-Hx-Hy dependence of the junction with uniform barrier. This Ic-Hx-Hy dependence has no hysteresis. In this study, we have first applied the external magnetic field Hz perpendicular to the junction plane and have obtained Ic-Hz characteristics using three pairs of Helmholtz coils. In the case that the perpendicular field Hz < 2400 A/m, the Ic-Hz characteristics have a little hysteresis. The shape of Ic-Hz characteristics was similar to the Fraunhofer pattern. In the case that the perpendicular field Hz > 2400 A/m, the Ic-Hz characteristics have strong hysteresis. The Josephson current Ic always disappeared in the case that Hz > 7000 A/m. Two recovering methods of this current Ic were (a) alternating Hz field and (b) heating the sample to the room temperature and again cooling to the liquid He temperature.

Preparation and properties of visible light responsive Y3+ doped Bi5Nb3O15 photocatalysts for Ornidazole decomposition.

Nanoparticle of Bi(5)Nb(3)O(15) doped with Y(3+) was prepared for the first time by the sol-gel method combined with impregnation. The degradation of Ornidazole reacting with Y(3+)-Bi(5)Nb(3)O(15) was investigated to explore the feasibility of using Y(3+)-Bi(5)Nb(3)O(15) to treat antibiotics in wastewater. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV-vis diffuse reflectance spectrum and X-ray photoelectron spectroscopy. The results showed that the Y(3+)-Bi(5)Nb(3)O(15) exhibited single-crystalline orthorhombic structure with small particle size (20-100 nm); additionally, its UV-vis absorbance edges significantly shift to the visible-light region. The as-prepared nanoparticles exhibited a high photocatalytic activity in the decomposition of Ornidazole and several possible pathways of degradation of Ornidazole were proposed according to the results of ultra-performance liquid chromatography tandem mass spectrometry.

Modified detector tomography technique applied to a superconducting multiphoton nanodetector.

We present an experimental method to characterize multi-photon detectors with a small overall detection efficiency. We do this by separating the nonlinear action of the multiphoton detection event from linear losses in the detector. Such a characterization is a necessary step for quantum information protocols with single and multiphoton detectors and can provide quantitative information to understand the underlying physics of a given detector. This characterization is applied to a superconducting multiphoton nanodetector, consisting of an NbN nanowire with a bowtie-shaped subwavelength constriction. Depending on the bias current, this detector has regimes with single and multiphoton sensitivity. We present the first full experimental characterization of such a detector.