Sensitive Light Detectors Research Articles

Two-dimensional hybrid perovskite crystals for highly sensitive and stable UV light detector

Two-dimensional metal halide perovskites (2D MHPs) are promising candidates for ultraviolet (UV) light detection due to their narrow band gap and high stability in the air atmosphere. MHP crystals, with fewer defects and grain boundaries than polycrystalline films, are more suitable for photodetectors and other advanced semiconductor devices. In this paper, aimed to fabricate high-performance UV light detector, a series of high-quality and large-sized 2D perovskite crystals with the composition of (BA)2Pb(ClxBr1-x)4 were prepared and the best UV responsibility was found in the (BA)2Pb(Cl0.1Br0.9)4 crystal. Despite the detector was fabricated by the simple silver brushing method, it exhibits high responsivity of 3.19 mA/W, high detection rate of 3.87 × 1011 Jones, and fast response speed to UV light of 340 nm under the bias of 20 V. Moreover, the detector shows remarkable light sensitivity even under extremely weak UV illumination of 5.4 μW/cm2 and satisfactory stability during a long-duration switching operation. The excellent light response performance of the (BA)2Pb(Cl0.1Br0.9)4 detector was ascribed to the very low dark current (0.84 pA) of the detector, which highly relies on the crystal quality of the light-absorbing perovskites. The relationship between the structural and the compositional characteristics of (BA)2Pb(Cl0.1Br0.9)4 and its light response property was analyzed. This work provides a promising candidate material for sensitive UV detection and high-performance photodetectors.

A simple, low-cost instrument for electrochemiluminescence immunoassays based on a Raspberry Pi and screen-printed electrodes

A powerful, yet low-cost and semi-portable electrochemiluminescence (ECL) biosensing device is described. It is constructed around a Raspberry Pi single-board computer, which serves as the controller and user interface. The Pi is interfaced with an expansion board that controls the potential applied to a disposable screen-printed electrode and facilitates data acquisition from a photomultiplier tube (PMT), which detects the ECL emission from the sensor surface. As proof-of-concept, we demonstrate that this arrangement can quantitate tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3]2+]) with an estimated limit of detection (LOD) of 20 pM, and C-reactive protein with an LOD of 50 fg mL−1. The analytical performance of the Raspberry Pi-based setup is comparable to a conventional ECL configuration (computer, potentiostat and photodetector). The Raspberry Pi-based setup can replace a conventional ECL setup, at a fraction of the cost, without sacrificing sensitivity or versatility. The combination of a single-board computer and a sensitive light detector represents a significant step towards translating ECL instruments into mobile, point-of-care diagnostic platforms.

Full Spectrum Flow Cytometry as a Powerful Technology for Cancer Immunotherapy Research.

The Nobel Prize-deserving concept of blocking inhibitory pathways in T cells, to unleash their anti-tumoral capacity, became one of the pillars of cancer treatment in the last decade and has resulted in durable clinical responses for multiple cancer types. Currently, two of the most important goals in cancer immunotherapy are to understand the mechanisms resulting in failure to checkpoint blockade and to identify predictive immunological biomarkers that correlate to treatment response, disease progression or adverse effects. The identification and validation of biomarkers for routine clinical use is not only critical to monitor disease or treatment progression, but also to personalize and develop new therapies. To achieve these goals, powerful research tools are needed. Flow cytometry stands as one of the most successful single-cell analytical tools used to characterize immune cell phenotypes to monitor solid tumors, hematological malignancies, minimal residual disease or metastatic progression. This technology has been fundamental in diagnosis, treatment and translational research in cancer clinical trials. Most recently, the need to evaluate simultaneously more features in each cell has pushed the field to implement more powerful adaptations beyond conventional flow cytometry, including Full Spectrum Flow Cytometry (FSFC). FSFC captures the full emission spectrum of fluorescent molecules using arrays of highly sensitive light detectors, and to date has enabled characterization of 40 parameters in a single sample. We will summarize the contributions of this technology to the advancement of research in immunotherapy studies and discuss best practices to obtain reliable, robust and reproducible FSFC results.

Bioluminescence goes portable: recent advances in whole-cell and cell-free bioluminescence biosensors.

Recent advancements in synthetic biology, organic chemistry, and computational models have allowed the application of bioluminescence in several fields, ranging from well established methods for detecting microbial contamination to in vivo imaging to track cancer and stem cells, from cell-based assays to optogenetics. Moreover, thanks to recent technological progress in miniaturized and sensitive light detectors, such as photodiodes and imaging sensors, it is possible to implement laboratory-based assays, such as cell-based and enzymatic assays, into portable analytical devices for point-of-care and on-site applications. This review highlights some recent advances in the development of whole-cell and cell-free bioluminescence biosensors with a glance on current challenges and different strategies that have been used to turn bioassays into biosensors with the required analytical performance. Critical issues and unsolved technical problems are also highlighted, to give the reader a taste of this fascinating and challenging field.

A portable and high-sensitivity optical sensing system for detecting fluorescently labeled enterohaemorrhagic Escherichia coli Shiga toxin 2B-subunit.

We developed a stand-alone, real-time optical detection device capable of reading fluorescence intensities from cell samples with high sensitivity and precision, for use as a portable fluorescent sensor for sensing fluorescently labeled enterohemorrhagic Escherichia coli (EHEC) Shiga toxins (Stxs). In general, the signal intensity from the fluorescently labeled Stxs was weak due to the small number of molecules bound to each cell. To address this technical challenge, we used a highly sensitive light detector (photomultiplier tube: PMT) to measure fluorescence, and designed a portable optical housing to align optical parts precisely; the housing itself was fabricated on a 3D printer. In addition, an electric circuit that amplified PMT output was designed and integrated into the system. The system shows the toxin concentration in the sample on a liquid crystal display (LCD), and a microcontroller circuit is used to read PMT output, process data, and display results. In contrast to other portable fluorescent detectors, the system works alone, without any peripheral computer or additional apparatus; its total size is about 17 × 13 × 9 cm3, and it weighs about 770 g. The detection limit was 0.01 ppm of Alexa Fluor 488 in PBS, which is ten thousand times lower than those of other smartphone-based systems and sufficiently sensitive for use with a portable optical detector. We used the portable real-time optical sensing system to detect Alexa Fluor 488–tagged Stx2B-subunits bound to monocytic THP-1 cells expressing the toxin receptor globotriaosylceramide (Gb3). The device did not detect a signal from Gb3-negative PD36 cells, indicating that it was capable of specifically detecting Stxs bound to cells expressing the toxin receptor. Following the development of a rapid and autonomous method for fluorescently tagging cells in food samples, the optical detection system described here could be used for direct detection of Shiga toxins in food in the field.

In-situ one pot synthesis of graphene-ZnO nanohybrid and its application to UV light detection

The development of molecular/nanoscale level assemblies allows the foundation of many potential novel applications. Chemical approach is one of the most favoured techniques to manipulate the nano-materials in a controllable manner. Herein, we report a simple and reliable one pot technique for preparing graphene-ZnO nanohybrid by coordinating zinc metal ions from precursor, which further led to the growth of ZnO nanoparticles on graphene sheets. The developed heterostructures were characterized through X-ray diffractometry, Fourier transformed infra-red (FTIR) spectroscopy, UV-visible spectroscopy and field emission scanning electron microscopy (FESEM). Morphological details revealed the dense loading of ZnO nanoparticles onto the surface of graphene. The nanohybrid was found to be electrically more responsive to the incident UV light compared to ZnO nanoparticles alone. The proposed method can lead to the fabrication of highly sensitive flexible light detector.

Estudio de la señal de salida y diseño de la red de polarización de tubos fotomultiplicadores

Se realiza un análisis de los factores intervinientes en la formación de la señal de los tubos fotomultiplicadores. Estos dispositivos son detectores de luz extremadamente sensibles, muy utilizados en aplicaciones de conteo de fotones. Se aborda el estudio y diseño de la red de polarización de los tubos fotomultiplicadores, sentando las bases para pruebas de desempeño. A través del análisis detallado del funcionamiento de los tubos fotomultiplicadores y su electrónica de polarización, se espera que el usuario pueda separar la respuesta del circuito de polarización de la información que llevan los pulsos de salida.

Light on the cell cycle of the non-photosynthetic bacterium Ramlibacter tataouinensis

Ramlibacter tataouinensis TTB310, a non-photosynthetic betaproteobacterium isolated from a semi-arid region of southern Tunisia, forms both rods and cysts. Cysts are resistant to desiccation and divide when water and nutrients are available. Rods are motile and capable of dissemination. Due to the strong correlation between sunlight and desiccation, light is probably an important external signal for anticipating desiccating conditions. Six genes encoding potential light sensors were identified in strain TTB310. Two genes encode for bacteriophytochromes, while the four remaining genes encode for putative blue light receptors. We determined the spectral and photochemical properties of the two recombinant bacteriophytochromes RtBphP1 and RtBphP2. In both cases, they act as sensitive red light detectors. Cyst divisions and a complete cyst-rod-cyst cycle are the main processes in darkness, whereas rod divisions predominate in red or far-red light. Mutant phenotypes caused by the inactivation of genes encoding bacteriophytochromes or heme oxygenase clearly show that both bacteriophytochromes are involved in regulating the rod-rod division. This process could favor rapid rod divisions at sunrise, after dew formation but before the progressive onset of desiccation. Our study provides the first evidence of a light-based strategy evolved in a non-photosynthetic bacterium to exploit scarse water in a desert environment.

Graphene-Assisted Growth of Patterned Perovskite Films for Sensitive Light Detector and Optical Image Sensor Application.

Controlled growth of high-quality patterned perovskite films on a large scale is essentially required for the application of this class of materials in functional integrated devices and systems. Herein, graphene-assisted hydrophilic-hydrophobic surface-induced growth of Cs-doped FAPbI3 perovskite films with well-patterned shapes by a one-step spin-coating process is developed. Such a facile fabrication technique is compatible with a range of spin-coated perovskite materials, perovskite manufacturing processes, and substrates. By employing this growing method, controllable perovskite photodetector arrays are realized, which have not only prominent photoresponse properties with a responsivity and specific detectivity of 4.8 AW-1 and 4.2 × 1012 Jones, respectively, but also relatively small pixel-to-pixel variation. Moreover, the photodetectors array can function as an effective visible light image sensor with a decent spatial resolution. Holding the above merits, the proposed technique provides a convenient and effective pathway for large-scale preparation of patterned perovskite films for multifunctional application purposes.

An inverted planar solar cell with 13% efficiency and a sensitive visible light detector based on orientation regulated 2D perovskites

A merged annealing process based high quality 2D perovskite film and the corresponding PVSC with a PCE beyond 13%.

SINGLE: single photon sensitive cryogenic light detectors

Thermal detectors operated at few mK as calorimeters are a powerful tool for the study of rare particle physics processes. In order to implement particle identification, light detection can be effectively performed by means of other thermal detectors operated as light sensors. This configuration can be used also in large scale, thousand-channels setups, but the light sensors must be sensitive enough to detect few, possibly a single, photons. The SINGLE project described here aims at producing silicon based, large area devices that can be operated as thermal detectors with single-photon sensitivity, and demonstrate the reliability of the performance, scalability of the production process and integrability with present and next generation cryogenic experiments for the search for rare events.

Photoresistor based on ZnO nanorods grown on a p-type silicon substrate

Abstract In this work we discuss a method of preparation of a highly sensitive light detector based on ZnO nanorods. A photoresistor constructed by us is based on a heterojunction between high quality ZnO nanorods and high resistivity p-type Si used as a substrate for nanorods’ deposition. ZnO nanorods are grown by a modified version of a microwave assisted hydrothermal method which allows for growth of high quality ZnO nanorods in a few minutes. The obtained photoresistor responds to a wide spectral range of light starting from near infrared (IR) to ultraviolet (UV). Properties of the detector are evaluated. We propose the use of the detector as an optical switch.

How rods respond to single photons: Key adaptations of a G-protein cascade that enable vision at the physical limit of perception.

Rod photoreceptors are among the most sensitive light detectors in nature. They achieve their remarkable sensitivity across a wide variety of species through a number of essential adaptations: a specialized cellular geometry, a G-protein cascade with an unusually stable receptor molecule, a low-noise transduction mechanism, a nearly perfect effector enzyme, and highly evolved mechanisms of feedback control and receptor deactivation. Practically any change in protein expression, enzyme activity, or feedback control can be shown to impair photon detection, either by decreasing sensitivity or signal-to-noise ratio, or by reducing temporal resolution. Comparison of mammals to amphibians suggests that rod outer-segment morphology and the molecules and mechanism of transduction may have evolved together to optimize light sensitivity in darkness, which culminates in the extraordinary ability of these cells to respond to single photons at the ultimate limit of visual perception.

Energy resolution and efficiency of phonon-mediated kinetic inductance detectors for light detection

The development of sensitive cryogenic light detectors is of primary interest for bolometric experiments searching for rare events like dark matter interactions or neutrino-less double beta decay. Thanks to their good energy resolution and the natural multiplexed read-out, Kinetic Inductance Detectors (KIDs) are particularly suitable for this purpose. To efficiently couple KIDs-based light detectors to the large crystals used by the most advanced bolometric detectors, active surfaces of several cm2 are needed. For this reason, we are developing phonon-mediated detectors. In this paper, we present the results obtained with a prototype consisting of four 40 nm thick aluminum resonators patterned on a 2 × 2 cm2 silicon chip, and calibrated with optical pulses and X-rays. The detector features a noise resolution σE = 154 ± 7 eV and an (18 ± 2)% efficiency.

In2-XO3-Y 1D perpendicular nanostructure arrays as ultraviolet detector

The 1D perpendicular In2-xO3-y nanostructure arrays have been synthesized by using glancing angle deposition (GLAD) technique. A low deposition rate of 0.5 A°/S produced highly porous structure. The characteristics of junction defects and photocurrent were measured to verify the detector performance. The junction capacitance and charge retention due to presence of trap states in the device decreased with an increase in frequency. The high value of Dit∼ 5.5 × 1017 cm−2 eV−1 was calculated for the device. The detector processes low ideality factor of ∼2.04 at 300 K. The maximum photo responsivity of ∼15 A/W and internal gain of ∼47 were measured for the 1D In2-xO3-y based detector at ∼380 nm in UV region. The device shows very high current density ∼20 A/cm2 (−2 V, 300 K) under dark, which deflects to 32 A/cm2 due to illumination. Under white light on/off switching irradiation, the device operates with rise time of 1.9 s and decay time of 2.3 s. Therefore In2-xO3-y nanostructure arrays can be used as sensitive UV light detector.

Highly sensitive room temperature infrared hybrid organic-nanocrystal detector

In this paper we demonstrate a very sensitive near-infrared light detector device based on InAs nano crystals (NCs) acting as an optical gate on top of a high-mobility shallow two-dimensional electron gas channel. The ability to integrate electronics with the NCs using both top-down and bottom-up approaches allows to utilize the NCs unique quantum properties for future optoelectronic devices. We employ wet chemistry to self-assemble the organic monolayers and the NCs on top of the field effect transistor. By using shallow and very narrow channel, the device's quantum efficiency can go as high as 106V/W at room temperature, with a signal-to-noise ratio that enables sensitivity for very low photon power. We find that our experimental results are compatible with simulation. Lastly, the route to advance to the single photon detection limit is discussed.

Ultra-fast growth of the monocrystalline zinc oxide nanorods from the aqueous solution

A new inexpensive method of the ultra-fast growth of ZnO nanorods from the aqueous solution is described. This environment friendly and fully reproducible method allows growth of nanorods in about 1–3 min time on various substrates, without any catalyst or complexing agent. The substrates need to be coated with a layer of gold droplets, which nucleate the growth. Growth temperature does not exceed 50ºC and growth can be performed at atmospheric pressure. Deionised water and zinc acetate are used as oxygen and zinc precursors, respectively. The method is characterised by simplicity and allows regulating size of the ZnO nanorods in a large extent. Due to simplicity and safety of this method, it is suitable for industrial applications, i.e., in the construction of gas sensors or highly sensitive light detectors (changes of sample resistivity upon illumination).

Low-temperature light detectors: Neganov–Luke amplification and calibration

The simultaneous measurement of phonons and scintillation light induced by incident particles in a scintillating crystal such as CaWO4 is a powerful technique for the active rejection of background induced by γʼs and βʼs and even neutrons in direct Dark Matter searches. However, ≲1% of the energy deposited in a CaWO4 crystal is detected as light. Thus, very sensitive light detectors are needed for an efficient event-by-event background discrimination. Due to the Neganov–Luke effect, the threshold of low-temperature light detectors based on semiconducting substrates can be improved significantly by drifting the photon-induced electron–hole pairs in an applied electric field. We present measurements with low-temperature light detectors based on this amplification mechanism. The Neganov–Luke effect makes it possible to improve the signal-to-noise ratio of our light detectors by a factor of ∼9 corresponding to an energy threshold of ∼21 eV. We also describe a method for an absolute energy calibration using a light-emitting diode.

Enhancement of photomultiplier sensitivity with anti-reflective layers

Photomultipliers are fast, sensitive and low noise light detectors which operate across the ultraviolet–optical–near infra red region of the electromagnetic spectrum. Sensitivity is determined by the composition of the photocathode layer in which incident photons excite photoelectrons and the thickness of this layer. Incident light is partially reflected from and partially transmitted through the photocathode layer, which is typically ∼20 nm thick, and this energy is unavailable for photoelectron excitation, limiting sensitivity. Typical reflectance and transmittance values at 500 nm are 21% and 33%, respectively, for KCsSb; 27% and 24% for RbCsSb and 36% and 35% for Na2SbK : Cs. These substantial losses can be reduced by the addition of one or more transparent impedance matching layers between the photomultiplier tube (PMT) window and the photocathode, resulting in enhanced sensitivity without effecting the PMT geometry, photocathode deposition process or altering the acceptance angle of the photomultiplier. The impedance matching serves to reduce reflectance losses, increasing cathode absorptance. By using published measurements of the dispersive properties of bialkali and trialkali (S20) photocathode compositions, accurate modelling of the electromagnetic field distribution within the photocathode layer is possible. This model facilitates the prediction of the enhancement of sensitivity obtainable with an anti-reflective layer of zirconium dioxide (zirconia). The authors present the enhancement factors possible with standard bialkali and trialkali photocathode compositions using the material zirconia for impedance matching. Enhancement factors up to 27% and 38% are predicted for KCsSb and RbCsSb photocathodes, respectively, while an enhancement factor of up to 44% is predicted for the S20 photocathode.

High resolution patterning of nanoparticles by evaporative self-assembly enabled by in situ creation and mechanical lift-off of a polymer template

High-resolution patterning of nanostructured materials into open templates is limited by the processes of creation and removal of the necessary template. In this work, a process for forming a micropatterned template from cellulose acetate polymer in situ on the substrate is demonstrated. Nanoparticles are patterned by evaporative self-assembly, and the template is removed by mechanical means. The process is demonstrated by patterning zinc oxide nanoparticles on silicon and cyclic olefin copolymer substrates and by creating a highly sensitive ultraviolet light detector.