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Single impurities in insulators are now often used for quantum sensors and single photon sources, while nanoscale semiconductor doping features are being constructed for electrical contacts in quantum technology devices, implying that new methods for sensitive, non‐destructive imaging of single‐ or few‐atom structures are needed. X‐ray fluorescence (XRF) can provide nanoscale imaging with chemical specificity, and features comprising as few as 100 000 atoms have been detected without any need for specialized or destructive sample preparation. Presently, the ultimate limits of sensitivity of XRF are unknown – here, gallium dopants in silicon are investigated using a high brilliance, synchrotron source collimated to a small spot. It is demonstrated that with a single‐pixel integration time of 1 s, the sensitivity is sufficient to identify a single isolated feature of only 3000 Ga impurities (a mass of just 350 zg). With increased integration (25 s), 650 impurities can be detected. The results are quantified using a calibration sample consisting of precisely controlled numbers of implanted atoms in nanometer‐sized structures. The results show that such features can now be mapped quantitatively when calibration samples are used, and suggest that, in the near future, planned upgrades to XRF facilities might achieve single‐atom sensitivity. [ABSTRACT FROM AUTHOR]

Organic semiconductors are a promising material candidate for X‐ray detection. However, the low atomic number (Z) of organic semiconductors leads to poor X‐ray absorption thus restricting their performance. Herein, the authors propose a new strategy for achieving high‐sensitivity performance for X‐ray detectors based on organic semiconductors modified with high –Z heteroatoms. X‐ray detectors are fabricated with p‐type organic semiconductors containing selenium heteroatoms (poly(3‐hexyl)selenophene (P3HSe)) in blends with an n‐type fullerene derivative ([6,6]‐Phenyl C71 butyric acid methyl ester (PC70BM). When characterized under 70, 100, 150, and 220 kVp X‐ray radiation, these heteroatom‐containing detectors displayed a superior performance in terms of sensitivity up to 600 ± 11 nC Gy−1 cm−2 with respect to the bismuth oxide (Bi2O3) nanoparticle (NP) sensitized organic detectors. Despite the lower Z of selenium compared to the NPs typically used, the authors identify a more efficient generation of electron‐hole pairs, better charge transfer, and charge transport characteristics in heteroatom‐incorporated detectors that result in this breakthrough detector performance. The authors also demonstrate flexible X‐ray detectors that can be curved to a radius as low as 2 mm with low deviation in X‐ray response under 100 repeated bending cycles while maintaining an industry‐standard ultra‐low dark current of 0.03 ± 0.01 pA mm−2. [ABSTRACT FROM AUTHOR]

The development of perovskite solar cells (PSCs) with low recombination losses at low processing temperatures is an area of growing research interest as it enables compatibility with roll‐to‐roll processing on flexible substrates as well as with tandem solar cells. The inverted or p–i–n device architecture has emerged as the most promising PSC configuration due to the possibility of using low‐temperature processable organic hole‐transport layers and more recently, self‐assembled monolayers such as [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz). However, devices incorporating these interlayers suffer from poor wettability of the precursor leading to pin hole formation and poor device yield. Herein, the use of alumina nanoparticles (Al2O3 nanoparticles (NPs)) for pinning the perovskite precursor on Me‐4PACz is demonstrated, thereby improving the device yield. While similar wettability enhancements can also be achieved by using poly[(9,9‐bis(3′‐((N,N‐dimethyl)‐N‐ethylammonium)‐propyl)‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene)]dibromide (PFN‐Br), a widely employed surface modifier, the incorporation of Al2O3 NPs results in significantly enhanced Shockley–Read–Hall recombination lifetimes exceeding 3 μs, which is higher than those on films coated directly on Me‐4PACz and on PFN‐Br‐modified Me‐4PACz. This translates to a champion power conversion efficiency of 19.9% for PSCs fabricated on Me‐4PACz modified with Al2O3, which is a ≈20% improvement compared to the champion device fabricated on PFN‐Br‐modified Me‐4PACz. [ABSTRACT FROM AUTHOR]

We report a facile, solvent-free surfactant-dependent mechanochemical synthesis of highly luminescent CsPbBr3 nanocrystals (NCs) and study their scintillation properties. A small amount of surfactant oleylamine (OAM) plays an important role in the two-step ball milling method to control the size and emission properties of the NCs. The solid-state synthesized perovskite NCs exhibit a high photoluminescence quantum yield (PLQY) of up to 88% with excellent stability. CsPbBr3 NCs capped with different amounts of surfactant were dispersed in toluene and mixed with polymethyl methacrylate (PMMA) polymer and cast into scintillator discs. With increasing concentration of OAM during synthesis, the PL yield of CsPbBr3/PMMA nanocomposite was increased, which is attributed to reduced NC aggregation and PL quenching. We also varied the perovskite loading concentration in the nanocomposite and studied the resulting emission properties. The most intense PL emission was observed from the 2% perovskite-loaded disc, while the 10% loaded disc exhibited the highest radioluminescence (RL) emission from 50 kV X-rays. The strong RL yield may be attributed to the deep penetration of X-rays into the composite, combined with the large interaction cross-section of the X-rays with the high-Z atoms within the NCs. The nanocomposite disc shows an intense RL emission peak centered at 536 nm and a fast RL decay time of 29.4 ns. Further, we have demonstrated the X-ray imaging performance of a 10% CsPbBr3 NC-loaded nanocomposite disc. [ABSTRACT FROM AUTHOR]

Curved X‐ray detectors have the potential to revolutionize diverse sectors due to benefits such as reduced image distortion and vignetting compared to their planar counterparts. While the use of inorganic semiconductors for curved detectors are restricted by their brittle nature, organic–inorganic hybrid semiconductors which incorporated bismuth oxide nanoparticles in an organic bulk heterojunction consisting of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and [6,6]‐phenyl C71 butyric acid methyl ester (PC70BM) are considered to be more promising in this regard. However, the influence of the P3HT molecular weight on the mechanical stability of curved, thick X‐ray detectors remains less well understood. Herein, high P3HT molecular weights (>40 kDa) are identified to allow increased intermolecular bonding and chain entanglements, resulting in X‐ray detectors that can be curved to a radius as low as 1.3 mm with low deviation in X‐ray response under 100 repeated bending cycles while maintaining an industry‐standard dark current of <1 pA mm−2 and a sensitivity of ≈ 0.17 μC Gy−1 cm−2. This study identifies a crucial missing link in the development of curved detectors, namely the importance of the molecular weight of the polymer semiconductors used. [ABSTRACT FROM AUTHOR]

Typically used semiconducting metal oxides (SMOs) consist of several varying factors that affect gas sensor response, including film thickness, grain size, and notably the grain–grain junctions within the active device volume, which complicates the analysis and optimisation of sensor response. In comparison, devices containing a single nanostructured element do not present grain–grain junctions, and therefore present an excellent platform to comprehend the correlation between nanostructure surface stoichiometry and sensor response to the depletion layer (Debye length, LD) variation after the analyte gas adsorption/chemisorption. In this work, nanofabricated devices containing SnO2 and Sn3O4 individual nanobelts of different thicknesses were used to estimate their LD after NO2 exposure. In the presence of 40 ppm of NO2 at 150 °C, LD of 12 nm and 8 nm were obtained for SnO2 and Sn3O4, respectively. These values were associated to the sensor signals measured using multiple nanobelts onto interdigitated electrodes, outlining that the higher sensor signal of the Sn4+ surface (up to 708 for 100 ppm NO2 at 150°) in comparison with the Sn2+ (up to 185) can be explained based on a less depleted initial state and a lower surface electron affinity caused by the Lewis acid/base interactions with oxygen species from the baseline gas. To support the proposed mechanisms, we investigated the gas sensor response of SnO2 nanobelts with a higher quantity of oxygen vacancies and correlated the results to the SnO system. [ABSTRACT FROM AUTHOR]

Organic‐inorganic hybrid semiconductors are an emerging class of materials for direct conversion X‐ray detection due to attractive characteristics such as high sensitivity and the potential to form conformal detectors. However, existing hybrid semiconductor X‐ray detectors display dark currents that are 1000–10 000× higher than industrially relevant values of 1–10 pA mm−2. Herein, ultra‐low dark currents of <10 pA mm−2, under electric fields as high as ≈4 V µm−1, for hybrid X‐ray detectors consisting of bismuth oxide nanoparticles (for enhanced X‐ray attenuation) incorporated into an organic bulk heterojunction consisting of p‐type Poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and n‐type [6,6]‐Phenyl C71 butyric acid methyl ester (PC70BM) are reported. Such ultra‐low dark currents are realized through the enrichment of the hole selective p‐type organic semiconductor near the anode contact. The resulting detectors demonstrate broadband X‐ray response including an exceptionally high sensitivity of ≈1.5 mC Gy−1 cm−2 and <6% variation in angular dependence response under 6 MV hard X‐rays. The above characteristics in combination with excellent dose linearity, dose rate linearity, and reproducibility over a broad energy range enable these detectors to be developed for medical and industrial applications. [ABSTRACT FROM AUTHOR]

A high‐rate capability carbon‐encapsulated polyaniline (PANI) composite is fabricated by a novel electrodeposition method of polyaniline on a carbon nanotube (CNT) forest, grown on carbon paper. This is followed by coating of an amorphous carbon layer via hydrothermal carbonization (HTC) of glucose, forming a three‐layer structure. We demonstrate that a slow scan rate, voltage‐restricted electrodeposition process can be used to produce a uniform PANI coating on individual CNTs throughout the network. The CNT forest structure offers excellent electronic and structural connection for the PANI nanofiber network, while the coating of amorphous carbon reduces electrode resistance, promoting enhanced electrochemical performance and reinforced structural stability during charging and discharging. The as‐prepared CNT/PANI/HTC composite exhibited a high specific capacitance of 571 F g−1 at 1 A g−1, and 557 F g−1 at 100 A g−1,whilst demonstrating a record rate capability of 98% capacitance retention, when the current density is increased 100‐fold. This advanced rate performance indicates that a slow electrodeposition process produces an electrochemically stable three‐layer composite with enhanced diffusion kinetics. Hence, the method developed in this work establishes further control on the electrochemical deposition of energy storage materials, for high‐rate capability. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) can be used in many different applications. Field emission (FE) measurements were used together with Raman spectroscopy to show a correlation between the microstructure and field emission parameters. However, field emission characterization does not suffer from fluorescence noise present in Raman spectroscopy. In this study, Raman spectroscopy is used to characterize vertically aligned CNT forest samples based on their D/G band intensity ratio (ID/IG), and FE properties such as the threshold electric field, enhancement coefficient, and anode to CNT tip separation (ATS) at the outset of emission have been obtained. A relationship between ATS at first emission and the enhancement factor, and, subsequently, a relationship between ATS and the ID/IG are shown. Based on the findings, it is shown that a higher enhancement factor (∼3070) results when a lower ID/IG is present (0.45), with initial emissions at larger distances (∼47 μm). For the samples studied, the morphology of the CNT tips did not play an important role; therefore, the field enhancement factor (β) could be directly related to the carbon nanotube structural properties such as breaks in the lattice or amorphous carbon content. Thus, this work presents FE as a complementary tool to evaluate the quality of CNT samples, with the advantages of a larger probe size and an averaging over the whole nanotube length. Correspondingly, one can find the best field emitter CNT according to its ID/IG. [ABSTRACT FROM AUTHOR]

Micro-supercapacitors are an important class of energy storage devices for portable, self-powered and miniaturized electronics such as sensors, biomedical implants and RFID tags. To address the issue of limited energy density of micro-supercapacitors, pseudocapacitive transition-metal oxides have been used as electrodes at the cost of lower power capability due to their low electronic conductivity. In this work, high-energy-density and high-power-density nickel(II) oxide (NiO) micro-supercapacitors, fabricated through inkjet printing, are demonstrated. The nanoparticle-based thin film NiO electrodes showed up to 14 orders of magnitude higher electrical conductivity than single crystal NiO. The enhanced conductivity of the electrodes was reflected in the low relaxation time constant of just 30 ms, which is among the lowest achieved for any supercapacitor. A magnesium perchlorate-based aqueous electrolyte with extended operating voltage window was developed to enable the operation of the devices up to 1.5 V. The devices showed remarkable areal and volumetric specific capacitances of up to 155 mF cm−2 and 705 F cm−3 respectively, surpassing the state-of-the-art inkjet-printed supercapacitors but also a few of the best micro-supercapacitors known to date. This work provides a compelling platform to simplify the fabrication process of micro-supercapacitors, with focus on digital design, scalable manufacturing, and direct integration with printed electronics. [ABSTRACT FROM AUTHOR]

SnO 2 -based varistors have been considered promising technological devices. However their practical application is usually stated as limited to high voltage circuits based on the high breakdown electric field exhibited by these ceramics. Recently, authors have shown that the insertion of one-dimensional (1D) SnO 2 belts allows overcoming this limitation. In this work, we present a detailed study of the growth mechanism of the belts inside varistors using electron microscopy techniques. We were able to show that mass transport has an intrinsic dependence on the sintering time and requires similar crystalline structure between the belts and the matrix. Dual beam and high-resolution transmission electron microscopy techniques permitted determining that 3D growth of belts occurs by coalescence. [ABSTRACT FROM AUTHOR]

This paper presents the results of a thorough study conducted on the action mechanism of one-dimensional single-crystalline SnO 2 nanobelts in decreasing the breakdown electric field (E b ) in SnO 2 -based varistors. The proposed method has general validity in that our investigation was focused on the traditional varistor composition SnO 2 -CoO-Cr 2 O 3 -Nb 2 O 5 . To accomplish our study objective, two methods of decreasing E b value were compared; one involving the increase in average grain size of the varistor through the sintering time and the other one related to the addition of nanobelts. The morphological results show that the method involving the increase in average grain size is limited by the formation of intragranular pores. Furthermore, despite contributing successfully towards decreasing the E b value (which underwent a decline from 3990 V cm −1 to 1133 V cm −1 with an increase in sintering time from 1 h to 2 h), the reduction obtained by this method is found to be much lower compared to that obtained via the nanobelts insertion method (E b = 270 V cm −1 ). Impedance spectroscopy results showed that the insertion of nanobelts caused a decline in the grain boundary resistance while surface potential measurements proved that this decline in resistance is attributed to the absence of potential barriers along the belts which leads to the formation of a lower resistance percolation path in the varistor. [ABSTRACT FROM AUTHOR]

In this study, individual nanofabricated SnO micro-disks, previously shown to exhibit exceptional sensitivity to NOx, are investigated to further our understanding of gas sensing mechanisms. The SnO disks presenting different areas and thickness were isolated and electrically connected to metallic electrodes aided by a Dual Beam Microscope (SEM/FIB). While single micro-disk devices were found to exhibit short response and recovery times and low power consumption, large interconnected arrays of micro-disks exhibit much higher sensitivity and selectivity. The source of these differences is discussed based on the gas/solid interaction and transport mechanisms, which showed that thickness plays a major role during the gas sensing of single-devices. The calculated Debye length of the SnO disk in presence of NO2 is reported for the first time. [ABSTRACT FROM AUTHOR]

We report a facile, solvent-free surfactant-dependent mechanochemical synthesis of highly luminescent CsPbBr 3 nanocrystals (NCs) and study their scintillation properties. A small amount of surfactant oleylamine (OAM) plays an important role in the two-step ball milling method to control the size and emission properties of the NCs. The solid-state synthesized perovskite NCs exhibit a high photoluminescence quantum yield (PLQY) of up to 88% with excellent stability. CsPbBr 3 NCs capped with different amounts of surfactant were dispersed in toluene and mixed with polymethyl methacrylate (PMMA) polymer and cast into scintillator discs. With increasing concentration of OAM during synthesis, the PL yield of CsPbBr 3 /PMMA nanocomposite was increased, which is attributed to reduced NC aggregation and PL quenching. We also varied the perovskite loading concentration in the nanocomposite and studied the resulting emission properties. The most intense PL emission was observed from the 2% perovskite-loaded disc, while the 10% loaded disc exhibited the highest radioluminescence (RL) emission from 50 kV X-rays. The strong RL yield may be attributed to the deep penetration of X-rays into the composite, combined with the large interaction cross-section of the X-rays with the high-Z atoms within the NCs. The nanocomposite disc shows an intense RL emission peak centered at 536 nm and a fast RL decay time of 29.4 ns. Further, we have demonstrated the X-ray imaging performance of a 10% CsPbBr 3 NC-loaded nanocomposite disc., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Typically used semiconducting metal oxides (SMOs) consist of several varying factors that affect gas sensor response, including film thickness, grain size, and notably the grain-grain junctions within the active device volume, which complicates the analysis and optimisation of sensor response. In comparison, devices containing a single nanostructured element do not present grain-grain junctions, and therefore present an excellent platform to comprehend the correlation between nanostructure surface stoichiometry and sensor response to the depletion layer (Debye length, LD) variation after the analyte gas adsorption/chemisorption. In this work, nanofabricated devices containing SnO2 and Sn3O4 individual nanobelts of different thicknesses were used to estimate their LD after NO2 exposure. In the presence of 40 ppm of NO2 at 150 °C, LD of 12 nm and 8 nm were obtained for SnO2 and Sn3O4, respectively. These values were associated to the sensor signals measured using multiple nanobelts onto interdigitated electrodes, outlining that the higher sensor signal of the Sn4+ surface (up to 708 for 100 ppm NO2 at 150°) in comparison with the Sn2+ (up to 185) can be explained based on a less depleted initial state and a lower surface electron affinity caused by the Lewis acid/base interactions with oxygen species from the baseline gas. To support the proposed mechanisms, we investigated the gas sensor response of SnO2 nanobelts with a higher quantity of oxygen vacancies and correlated the results to the SnO system.