Carbon Nanotubes and Graphene Powder based Multifunctional Pressure,Displacement and Gradient of Temperature Sensors

Semiconductors - This work presents the fabrication and investigation of the multiwalled carbon nanotubes (MWCNTs) and graphene pristine powders based multifunctional pressure, displacement and...     

Black Phosphorus@Laser-Engraved Graphene Heterostructure-Based Temperature–Strain Hybridized Sensor for Electronic-Skin Applications

Smart electronic skin (e-skin) requires the easy incorporation of multifunctional sensors capable of mimicking skin-like perception in response to external stimuli. However, efficient and reliable measurement of multiple parameters in a single functional device is limited by the sensor layout and choice of functional materials. The outstanding electrical properties of black phosphorus and laser-engraved graphene (BP@LEG) demonstrates a new paradigm for a highly sensitive dual-modal temperature and strain sensor platform to modulate e-skin sensing functionality. Moreover, the unique hybridized sensor design enables efficient and accurate determination of each parameter without interfering with each other. The cationic polymer passivated BP@LEG composite material on polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) substrate outperforms as a positive temperature coefficient material, exhibiting a high thermal index of 8106 K (25–50  ° C) with high strain sensitivity (i.e., gauge factor, GF) of up to 2765 ( > 19.2%), ultralow strain resolution of 0.023%, and longer durability ( > 18 400 cycles), satisfying the e-skin requirements. Looking forward, this technique provides unique opportunities for broader applications, such as e-skin, robotic appendages, and health monitoring technologies.     

Polyaziridine-Encapsulated Phosphorene-Incorporated Flexible 3D Porous Graphene for Multimodal Sensing and Energy Storage Applications

Heteroatom-incorporated graphene represents a prominent family of materials utilized as active electrodes for multimodal sensing and energy storage applications. Herein, a novel polyaziridine-encapsulated phosphorene (PEP)-incorporated flexible 3D porous graphene (3DPG) electrode is developed using facile, cost-effective laser writing, and drop-casting techniques. Owing to the excellent electrochemical characteristics and surface functionality of the highly stable PEP, the fabricated PEP/3DPG is evaluated as a potential electrode for immunosensing, electrocardiogram (ECG) recording, and microsupercapacitors (MSCs). Under optimized conditions, the produced PEP/3DPG-based carcinoembryonic immunosensor exhibits linear ranges of 0.1–700 pg mL⁻¹ and 1–100 ng mL⁻¹ with a detection limit of 0.34 pg mL⁻¹ and high selectivity. The finger touch-based ECG sensor demonstrates a relatively low and stable impedance at the skin-electrode interface; therefore, the signal-to-noise ratio of the ECG signal received from the fabricated sensor (13.5 dB) is comparable to that of conventional Ag/AgCl electrodes (13.9 dB). Besides, the highest areal capacitance of the prepared MSC reached a magnitude of 16.94 mF cm⁻², which is six times higher than that of a non-doped 3DPG-based MSC. These results demonstrate the effectiveness of the described fabrication procedure and the high utilization potential of the encapsulated phosphorene-doped 3D graphene in multimodal applications.     

Thermal neutron imaging with rare-earth-ion-doped LiCaAlF6 scintillators and a sealed Cf source

Thermal neutron imaging with Ce-doped LiCaAlF₆ crystals has been performed. The prototype of the neutron imager using a Ce-doped LiCaAlF₆ scintillating crystal and a position sensitive photomultiplier tube (PSPMT) which had 64 multi-channel anode was developed. The Ce-doped LiCaAlF₆ single crystal was grown by the Czochralski method. A plate with dimensions of a diameter of 50×2 mm² was cut from the grown crystal, polished, and optically coupled to PSPMT by silicone grease. The ²⁵²Cf source (<1 MBq) was sealed with 43 mm of polyethylene for neutron thermalization. Alphabet-shaped Cd pieces with a thickness of 2 mm were used as a mask for the thermal neutrons. After corrections for the pedestals and gain of each pixel, we successfully obtained two-dimensional neutron images using Ce-doped LiCaAlF₆.     

Crystal growth and characterization of Tm doped mixed rare-earth aluminum perovskite

In this work, we present results of structural characterization and optical properties including radio luminescence of (Lu_xGd_yY_0.99?x?yTm_0.01)AP single crystal scintillators for (x, y) = (0.30, 0.19), (0, 0.19) and (0, 0) grown by the micro-pulling-down (μ-PD) method. The grown crystals were single phase materials with perovskite structure (Pbnm) as confirmed by XRD and had a good crystallinity. The distribution of the crystal constituents in growth direction was evaluated, and significant segregation of Lu and Gd was detected in (Lu_0.30Gd_0.19Y_0.50Tm_0.01)AP sample. The crystals demonstrated 70% transmittance in visible wavelength range and some absorption bands due to Tm³⁺, Gd³⁺ and color centers were exhibited in 190–900 nm. The radioluminescence measurement under X-ray irradiation demonstrated several emission peaks ascribed to 4f–4f transitions of Tm³⁺ and Gd³⁺. The ratio of emission intensity in longer wavelength range was increased when Y was replaced by Lu or Gd.     

Growth and characterization of strontium metaborate scintillators

The undoped and 0.5% Ce³⁺-doped strontium metaborate SrB₂O₄ single crystals has been grown successfully by micro-pulling down method with radio frequency (RF) heating system, and scintillation characteristics including optical properties and radiation response were studied for these crystals. The Ce³⁺-doped SrB₂O₄ crystal showed absorption band around 240–320 nm, which is corresponding to the 4f-5d transition of Ce³⁺. Intense emission band at 375 nm due to the Ce³⁺ 5d–4f transition was observed under ²⁴¹Am 5.5 MeV α-ray excitation. The scintillation decay time showed fast (50 ns) and slow (1430 ns) components ascribed to the Ce³⁺ 5d–4f transition and lattice defect in the crystal, respectively. The scintillation light yield of Ce³⁺-doped SrB₂O₄ was calculated to be about 1000 ph/n under ²⁵²Cf irradiation.     

Crystal growth and scintillation characteristics of the Nd doped LiLuF4 single crystals

Sixty millimeter diameter single crystal of Nd³⁺ doped LiLuF₄ was successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous luminescence characteristics were found from X-ray rocking curve and cathode-ray luminescence respectively. X-ray excited luminescence spectrum was measured and the significant 4f²5d-4f³ luminescence at 182 nm was observed in the grown crystal. The pulse height spectrum was taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray showing the light yield of 420 ± 30 photons/MeV. The decay curve under α-ray irradiation was also investigated and described by two component decay kinetics which consists of the decay constants of 34 and 450 ns.     

Crystal growth and optical properties of the Nd doped LuF3 single crystals

Thirty millimeter diameter single crystal of Nd³⁺ doped LuF₃ was grown using LiF as solvent. The single phase crystallization was confirmed by the powder X-ray diffraction, and high structural perfection was demonstrated by X-ray rocking curve (XRC) measurements. FWHM of XRC for 220 reflection was 32 arcsec. No remarkable absorption due to unfavorable impurities was observed from optical absorption measurements in the VUV spectral region. The crystal showed the VUV luminescence peaking around 178 nm that is consistent with the 4f²5d-4f³ transition of Nd³⁺ ion. The luminescence intensity of Nd:LuF₃ under X-ray irradiation was significantly higher than that of reported VUV scintillators such as Nd:LaF₃ or Nd:LiLuF₄.     

Basic study of single crystal fibers of Pr:Lu3Al5O12 scintillator for gamma-ray imaging applications

Single-crystalline fibers were grown from 0.25, 0.70, and 1.50 mol% Pr-doped Lu₃Al₅O₁₂ (LuAG) melts by the micro-pulling down (μ-PD) method with a diameter of 0.3-0.5 mm and a length of about 200 mm. They were cut to 10 mm long specimens, and their scintillation properties, including light yield and decay time profile, were examined. These results were compared with corresponding properties of the specimens (0.8×0.8×10 mm³) cut from the bulk crystals produced by conventional Czochralski (CZ) growth. The μ-PD-grown fibers demonstrated relatively low light yield and had the same decay time constant when compared with those of the samples cut from the CZ-grown crystals. The fiber crystals were used to assemble scintillating arrays with dimensions of Ø 0.5×10 mm²×20 pixels and Ø 0.3×10 mm²×30 pixels coated by a BaSO₄ reflector. After optical coupling with a position sensitive photomultiplier tube, the fiber-based arrays demonstrated acceptable imaging capability with a spatial resolution of about 0.5 mm.