Double perovskite Cs2AgBiBr6 radiation sensor: synthesis and characterization of single crystals

Single crystals of lead-free halide double perovskite Cs2AgBiBr6 sensor material manifest a remarkable potential for application in radiation detection and imaging. In this study, the purity and crystallinity of solution-grown Cs2AgBiBr6 single crystals with cubic Fm$$\overline{3}$$ 3 ¯ m symmetry have been corroborated by powder XRD measurements, while the single crystal XRD patterns reveal the dominant {111} lattice planes parallel to the sample surfaces. A wider range of lower resistivity values (106–109 Ωcm) was obtained from the I-V measurements compared to the 1.55 × 109–6.65 × 1010 Ωcm values from the van der Pauw method, which is typically higher for the Ag than for the carbon paint electrodes. Charge-carrier mobility values estimated from the SCLC method for the carbon paint-Cs2AgBiBr6 (1.90–4.82 cm2V−1 s−1) and the Ag-Cs2AgBiBr6 (0.58–4.54 cm2V−1 s−1) including the density of trap states (109–1010 cm−3) are comparable. Similar values of 1.89 cm2V−1 s−1 and 2.36 cm2V−1 s−1 are derived from the Hall effect measurements for a sample with carbon and Ag electrodes, respectively. The key electrical parameters including the X-ray photoresponse measurements indicate that the Cs2AgBiBr6 samples synthesized in this study satisfy requirements for radiation sensors. Graphical abstract

Investigating a promising iron-doped graphene sensor for SO2 gas: DFT calculations and QTAIM analysis

Examination of a promising iron-doped graphene (FG) sensor for the sulfur oxide (SO2) toxic gas was done in this work at the molecular and atomic scales of density functional theory (DFT). The models were stabilized by performing optimization calculations and their electronic features were evaluated. Two models were obtained by relaxing each of the O or S atoms towards the Fe-doped region of surface. Energy values indicated higher strength for formation of the O@FG model in comparison with the S@FG model. The evaluated quantities and qualities of electronic molecular orbitals indicated the effects of occurrence of adsorption processes on the electronic conductivity property of FG as a required feature of a sensor material. As a consequence, the idea of proposing the investigated FG as a promising sensor of the hazardous SO2 gas was affirmed in this work based on the obtained structural and electronic features.

HEXITEC 2 × 2 tiled hard X-ray spectroscopic imaging detector system

HEXITEC is a spectroscopic imaging X-ray detector technology developed at the STFC Rutherford Appleton Laboratory for X-ray and γ-ray spectroscopic imaging applications. Each module has 80 × 80 pixels on a 250 μm pixel pitch, and has been implemented successfully in a number of applications. This paper presents the HEXITEC 2 × 2 detector system, a tiled array of 4 HEXITEC modules read out simultaneously, which provides an active area of 16 cm2. Systems have been produced using 1 mm thick Cadmium Telluride (CdTe) and 2 mm thick Cadmium Zinc Telluride (CdZnTe) sensor material. In this paper the system and data processing methods are presented, and the performance of the systems are evaluated. The detectors were energy calibrated using an 241Am sealed source. Three types of charge sharing correction were applied to the data-charge sharing addition (CSA), charge sharing discrimination (CSD), and energy curve correction (ECC) which compensates for energy lost in the inter-pixel region. ECC recovers an additional 34 % of counts in the 59.5 keV peak in CdTe compared to the use of CSD; an important improvement for photon-starved applications. Due to the high frame rate of the camera system (6.3 kHz) an additional End of Frame (EOF) correction was also applied to 6.0 % of events to correct for signals that were readout whilst the signal was still forming. After correction, both detector materials were found to have excellent spectroscopic performance with a mean energy resolution (FWHM) of 1.17 keV and 1.16 keV for CdZnTe and CdTe respectively. These results successfully demonstrate the ability to construct tiled arrays of HEXITEC modules to provide larger imaging areas.

Improvement of the detectivity in an Fe-Sn magnetic-field sensor with a large current injection

A ferromagnetic nanocrystalline Fe-Sn is an excellent platform for magnetic-field sensor based on anomalous Hall effect (AHE) owing to simple fabrication and superior thermal stability. For improvement of the magnetic-field sensitivity, doping impurity and increasing injection current are effective approaches. However, in the light of magnetic-field detectivity, the large current may increase the voltage noise. In this study, a maximum allowable current of was improved by employing the overlayer electrode configuration on a Ta-doped Fe-Sn AHE sensor. In noise measurements, the 1/f noise becomes significant with increasing the current at low frequency, resulting in saturation of the detectivity to 240 nTHz-1/2 at 120 Hz. At high frequency, the detectivity reaches 48 nTHz-1/2 at 3.1 mA showing ten times improvement of the detectivity compared with the non-doped Fe-Sn AHE sensor. Material design and device structure optimization will accelerate further improvement of the sensing properties of the Fe-Sn-based AHE sensor.

A large-area flexible tactile sensor for multi-touch and force detection using electrical impedance tomography

In this paper, a large-area flexible tactile sensor for multi-touch and force detection based on EIT technology was developed. A novel design of a sensor material made of a porous elastic polymer and ionic liquid was proposed. The proposed conductive flexible materials combining elastic porous structures and conductive liquids provide continuous, linear changes in impedance with respect to touch forces. A deep learning scheme PSPNet based on MobileNet was adopted to postprocess the originally reconstructed images to improve the performance of tactile perception. By using this data-driven method, we can improve the spatial resolution of the tactile sensor to achieve a single-point position detection error of 7.5±4.5 mm without using internal electrodes.

A large-area flexible tactile sensor for multi-touch and force detection using electrical impedance tomography

In this paper, a large-area flexible tactile sensor for multi-touch and force detection based on EIT technology was developed. A novel design of a sensor material made of a porous elastic polymer and ionic liquid was proposed. The proposed conductive flexible materials combining elastic porous structures and conductive liquids provide continuous, linear changes in impedance with respect to touch forces. A deep learning scheme PSPNet based on MobileNet was adopted to postprocess the originally reconstructed images to improve the performance of tactile perception. By using this data-driven method, we can improve the spatial resolution of the tactile sensor to achieve a single-point position detection error of 7.5±4.5 mm without using internal electrodes.

Thermodynamic Studies and Optimization of the Method for Obtaining Neodymium Fluoride for the Production of Magnetic Sensors’ Sensitive Elements

Rare earth metals (REM) with magnetic properties find application in the recently developed high-tech industries. Sensor magnetic systems based on neodymium are increasingly in demand in modern engineering and geological surveys due to their favorable combination of properties of magnetic materials based on rare earth metals. One of the problems is to obtain high-quality materials for the production of such magnetic sensors. It should be noted that the high activity of REM does not allow obtaining master alloys and REM-based alloys from metallic materials; it is advisable to use halide compounds. This work discusses a method for producing neodymium fluoride from its oxide. REM fluorides can be obtained by fluorinating the oxides of these metals. Various fluorine-containing compounds or elemental fluorine are usually used as fluorinating reagents, which have their own advantages and disadvantages. The thermodynamic and technological analysis of neodymium fluoride production processes has shown the most acceptable fluorinating agent is ammonium hydrofluoride, which was used in this work. In order to increase the productivity and degree of chemical transformation, it was proposed to perform heating stepwise; i.e., at the initial stage, heat at a speed of 3 degrees per minute, after which the heating speed was reduced to 2 degrees per minute, and finally the speed was reduced to 1 degree per minute. Due to proposed heating mode, the same productivity and yield of chemical transformation were achieved, with an increased efficiency up to 30%, which can significantly reduce the cost of production. The obtained product is used in the production of neodymium-based alloys by metallothermic reduction of a mixture of fluorides. The sensor material obtained in this way is characterized by a low (less than 0.05%) oxygen content.

Preparation of Eu0.075Tb0.925-Metal Organic Framework as a Fluorescent Probe and Application in the Detection of Fe3+ and Cr2O72−

Luminescent Ln-MOFs (Eu0.075Tb0.925-MOF) were successfully synthesised through the solvothermal reaction of Tb(NO3)3·6H2O, Eu(NO3)3·6H2O, and the ligand pyromellitic acid. The product was characterised by X-ray diffraction (XRD), TG analysis, EM, X-ray photoelectron spectroscopy (XPS), and luminescence properties, and results show that the synthesised material Eu0.075Tb0.925-MOF has a selective ratio-based fluorescence response to Fe3+ or Cr2O72−. On the basis of the internal filtering effect, the fluorescence detection experiment shows that as the concentration of Fe3+ or Cr2O72− increases, the intensity of the characteristic emission peak at 544 nm of Tb3+ decreases, and the intensity of the characteristic emission peak at 653 nm of Eu3+ increases in Eu0.075Tb0.925-MOF. The fluorescence intensity ratio (I653/I544) has a good linear relationship with the target concentration. The detection linear range for Fe3+ or Cr2O72− is 10–100 μM/L, and the detection limits are 2.71 × 10−7 and 8.72 × 10−7 M, respectively. Compared with the sensor material with a single fluorescence emission, the synthesised material has a higher anti-interference ability. The synthesised Eu0.075Tb0.925-MOF can be used as a highly selective and recyclable sensing material for Fe3+ or Cr2O72−. This material should be an excellent candidate for multifunctional sensors.