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1.
Talanta ; 236: 122839, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34635229

RESUMO

Single-cell analysis of proteins is critical to gain precise information regarding the mechanisms that dictate the heterogeneity in cellular phenotypes and their differential response to internal and external stimuli. However, tools that allow sensitive and easy measurement of proteins in individual cells are still limited. The emerging semiconductor-based bioelectronics may provide a new approach to overcome the challenges in this field, however its utility in single-cell protein analysis has not been explored. In this study, we investigated multiple protein detection in single cells by MoS2 field effect transistors (MoS2-FETs) modified with specific biological probes. First, ß-actin antibody was connected to the surface of MoS2-FETs by covalent bonds, and the fabricated device was tested using ß-actin solution with concentrations from 10-9 to 10-3 µg/µL. Next, we examined the application of MoS2-FET for protein analysis in complex biological samples, and the device showed electrical signal response to human embryonic kidney cell line HEK293T in a dose-dependent manner. Furthermore, we applied this method to analyze individual liver cancer MHCC-97L cells, targeting four cellular proteins, including ß-actin, epidermal growth factor receptor, sirtuin-2, and glyceraldehyde-3-phosphate dehydrogenase. The devices modified with corresponding probes could identify the target proteins and showed cell number-dependent responses. As a proof of principle, we demonstrated sensitive and multiplexed detection of proteins in single cells using MoS2-FETs. The biosensor and this detection method are cost-efficient and user-friendly with broad application prospects in biological studies and clinical diagnosis.


Assuntos
Técnicas Biossensoriais , Molibdênio , Células HEK293 , Humanos , Proteínas , Semicondutores
2.
Chemosphere ; 286(Pt 2): 131745, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34364232

RESUMO

Ceramic membranes with high chemical and fouling resistance can play a critical role in treating industrial wastewater. In the present study, we demonstrate the fabrication of graphene oxide (GO) assembled ceramic nanofiltration (NF) membranes that provide effective ammonium retention and excellent fouling resistance for treating semiconductor wastewater. The GO-ceramic NF membranes were prepared via a layer-by-layer (LbL) assembly of GO and polyethyleneimine (PEI) on a ceramic ultrafiltration (UF) substrate. The successful fabrication of the GO-ceramic NF membranes was verified through surface characterization and pore size evaluation. We also investigated the performance of GO-ceramic NF membranes assembled with different numbers of bilayers for the rejection of ammonium ions. GO-ceramic NF membranes with three GO-PEI bilayers exhibited 8.4- and 3.2-times higher ammonium removal with simulated and real semiconductor wastewater, respectively, compared to the pristine ceramic UF substrate. We also assessed flux recovery after filtration using real semiconductor wastewater samples to validate the lower fouling potential of the GO-ceramic NF membranes. Results indicate that flux recovery increases from 39.1 % in the pristine UF substrate to 71.0 % and 90.8 % for the three- and ten-bilayers GO-ceramic NF membranes, respectively. The low-fouling GO-ceramic NF membranes developed in this study are effective and promising options for the removal of ammonium ions from semiconductor wastewater.


Assuntos
Compostos de Amônio , Purificação da Água , Cerâmica , Grafite , Membranas Artificiais , Semicondutores , Águas Residuárias
3.
Food Chem ; 369: 130971, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34488130

RESUMO

A highly sensitive molecularly imprinted surface-enhanced Raman scattering (SERS) sensor was developed for selective detection of histamine. A combination of two semiconductors and Ag nanoparticles (NPs) was used as the SERS substrate. The SERS was induced by Ag NPs plasmon resonances as well as charge-transfer between the semiconductors and the Ag NPs. The Raman intensity and the logarithm of the histamine concentration were linear over the range 10-8-10-3 mol L-1. The sensor exhibited good selectivity and had a sensitivity limit of 3.088 × 10-9 mol L-1. Histamine was detected in a spiked liquor sample, and its recoveries were in the range of 89.89%-109.18%.


Assuntos
Nanopartículas Metálicas , Análise Espectral Raman , Histamina , Semicondutores , Prata
4.
Chemosphere ; 287(Pt 3): 132273, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34563773

RESUMO

In this research, the potential of bismuth chromate (BCO), a new bismuth-based semiconductor belongs to the family of Bi2XO6 (X = Mo, W, or Cr), was introduced by a novel 1D/2D structure consist of BCO nanobelts and N2-freezed ultra-wrinkled graphitic carbon nitride (N-CN) nanosheets. To enhance intimate contact between BCO and N-CN (BCO/N-CN composite), surface oxygen vacancy (VO) was created as an efficient electron transfer highway using a simple alkaline-treatment-assisted method. Various characterization techniques, including XRD, FT-IR, EPR, FE-SEM, TEM, BET, DRS, PL, EIS, and photocurrent transient analyses were conducted to elucidate the physicochemical aspects of catalysts. The synthesized catalysts were subjected to levofloxacin (LVFX) photodegradation and optimum conditions were found under LED irradiation. Under optimum conditions, about 92.5% of LVFX was catalytically degraded over VO-rich BCO/N-CN heterojunction after 120 min of reaction, which was 2.3 folds higher than that of VO-free composite. The obtained heterojunction maintained superior performance after five consecutive runs with no noticeable changes in the XRD and FT-IR patterns, demonstrating the high stability of synthesized nanocomposite. Thus, the proposed interfacial engineering in this study opens new insight for ameliorating the insufficient interfacial contact between components of heterojunctions. This study not only presents a new bismuth-based photocatalyst for antibiotic degradation but also sheds light on the charge migration behavior in favor of efficient Z-type heterojunction.


Assuntos
Bismuto , Oxigênio , Antibacterianos , Semicondutores , Espectroscopia de Infravermelho com Transformada de Fourier
5.
Sensors (Basel) ; 21(21)2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34770260

RESUMO

A three-axis micro magnetic sensor (MS) is developed based on the standard 180 nm complementary metal oxide semiconductor (CMOS) technology. The MS designs two magnetic sensing elements (MSEs), which consists of an x/y-MSE and an z-MSE, to reduce cross-sensitivity. The x/y-MSE is constructed by an x-MSE and an y-MSE that are respectively employed to detect in the x- and y-direction magnetic field (MF). The z-MSE is used to sense in the z-direction MF. The x/y-MSE, which is constructed by two magnetotransistors, designs four additional collectors that are employed to increase the sensing current and to enhance the sensitivity of the MS. The Sentaurus TCAD software simulates the characteristic of the MS. The measured results reveal that the MS sensitivity is 534 mV/T in the x-direction MF, 525 mV/T in the y-direction MF and 119 mV/T in the z-axis MF.


Assuntos
Óxidos , Semicondutores , Campos Magnéticos , Software , Tecnologia
6.
Sensors (Basel) ; 21(21)2021 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-34770377

RESUMO

The design of neural network architectures is carried out using methods that optimize a particular objective function, in which a point that minimizes the function is sought. In reported works, they only focused on software simulations or commercial complementary metal-oxide-semiconductor (CMOS), neither of which guarantees the quality of the solution. In this work, we designed a hardware architecture using individual neurons as building blocks based on the optimization of n-dimensional objective functions, such as obtaining the bias and synaptic weight parameters of an artificial neural network (ANN) model using the gradient descent method. The ANN-based architecture has a 5-3-1 configuration and is implemented on a 1.2 µm technology integrated circuit, with a total power consumption of 46.08 mW, using nine neurons and 36 CMOS operational amplifiers (op-amps). We show the results obtained from the application of integrated circuits for ANNs simulated in PSpice applied to the classification of digital data, demonstrating that the optimization method successfully obtains the synaptic weights and bias values generated by the learning algorithm (Steepest-Descent), for the design of the neural architecture.


Assuntos
Redes Neurais de Computação , Semicondutores , Algoritmos , Neurônios , Óxidos
7.
Artigo em Inglês | MEDLINE | ID: mdl-34769899

RESUMO

(1) Background: This study aimed to analyze the risk of chronic diseases including hypertension, diabetes, and dyslipidemia in workers of a semiconductor manufacturing company and the factors associated with their participation in workplace health promotion (WHP) programs. (2) Methods: Subjects were workers in a semiconductor and liquid crystal display company in South Korea who had undergone regular health checkups. Data from regular health checkups and WHP interventions were analyzed. Health risk was classified based on the diagnosed disease, in-house classification criteria, and pooled cardiovascular risk score. (3) Results: The baseline characteristics of 39,073 participants included the following: male, 67.8%; between 30 and 40 years of age, 74.1%; <2 h of physical activities, 65.9%. Workers at risk of chronic diseases accounted for 22.2%, and 20.1% were suspicious cases of chronic diseases. Body mass index, and cholesterol level were relatively high in workers with the burden of chronic diseases. The participation rate in WHP programs was 28.8% in a high-risk group among workers at risk of chronic diseases. More participation was shown in male, older age groups, production work type, and single-person household. (4) Conclusions: Because of the low participation rate in WHP activities among workers with the burden of chronic diseases, it is necessary to establish measures to encourage their participation.


Assuntos
Promoção da Saúde , Local de Trabalho , Idoso , Doença Crônica , Exercício Físico , Humanos , Masculino , Semicondutores
8.
Artigo em Inglês | MEDLINE | ID: mdl-34769740

RESUMO

Underreporting work-related musculoskeletal disorders (WRMSD) has been an issue in South Korea. The purpose of this survey was to figure out how many employees of a semiconductor and liquid crystal display company in South Korea experience WRMSDs and what the possible obstacles in reporting to the company are. A survey was developed with demographic questions, perceived WRMSD symptoms, and reasons for reporting or not reporting WRMSD. The survey was distributed via the company's intranet to all employees (24,380) whose employee identification number ended with an odd number. A total of 2862 employees completed the survey and the response rate was 11.7%. A total of 55.2% of respondents had felt at least one musculoskeletal symptom during the past year. More than 40% of workers who had experienced pain or discomfort during the past year thought their symptoms were more than 50%. work-related. More than one-fourth of respondents answered that they did not report their symptoms to the company more than once. The open-ended answers for not reporting WRMSD were categorized into seven common reasons. The reasons for not reporting WRMSD in previous studies show a combination of personal, organizational, socioeconomical, and cultural factors. To encourage and manage WRMSD effectively, seven recommendations of authors are described.


Assuntos
Doenças Musculoesqueléticas , Doenças Profissionais , Humanos , Doenças Musculoesqueléticas/epidemiologia , Doenças Profissionais/epidemiologia , República da Coreia/epidemiologia , Semicondutores , Inquéritos e Questionários
9.
Sensors (Basel) ; 21(22)2021 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-34833532

RESUMO

Methane is a major greenhouse gas and a precursor of tropospheric ozone, and most of its sources are linked to anthropogenic activities. The sources of methane are well known and its monitoring generally involves the use of expensive gas analyzers with high operating costs. Many studies have investigated the use of low-cost gas sensors as an alternative for measuring methane concentrations; however, it is still an area that needs further development to ensure reliable measurements. In this work a low-cost platform for measuring methane within a low concentration range was developed and used in two distinct environments to continuously assess and improve its performance. The methane sensor was the Figaro TGS2600, a metal oxide semiconductor (MOS) based on tin dioxide (SnO2). In a first stage, the monitoring platform was applied in a small ruminant barn after undergoing a multi-point calibration. In a second stage, the system was used in a wastewater treatment plant together with a multi-gas analyzer (Gasera One Pulse). The calibration of low-cost sensor was based on the relation of the readings of the two devices. Temperature and relative humidity were also measured to perform corrections to minimize the effects of these variables on the sensor signal and an active ventilation system was used to improve the performance of the sensor. The system proved to be able to measure low methane concentrations following reliable spatial and temporal patterns in both places. A very similar behavior between both measuring systems was also well noticeable at WWTP. In general, the low-cost system presented good performance under several environmental conditions, showing itself to be a good alternative, at least as a screening monitoring system.


Assuntos
Metano , Ozônio , Calibragem , Semicondutores , Temperatura
10.
Sensors (Basel) ; 21(22)2021 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-34833561

RESUMO

CMOS microelectronics design has evolved tremendously during the last two decades. The evolution of CMOS devices to short channel designs where the feature size is below 1000 nm brings a great deal of uncertainty in the way the microelectronics design cycle is completed. After the conceptual idea, developing a thinking model to understand the operation of the device requires a good "ballpark" evaluation of transistor sizes, decision making, and assumptions to fulfill the specifications. This design process has iterations to meet specifications that exceed in number of the available degrees of freedom to maneuver the design. Once the thinking model is developed, the simulation validation follows to test if the design has a good possibility of delivering a successful prototype. If the simulation provides a good match between specifications and results, then the layout is developed. This paper shows a useful open science strategy, using the Excel software, to develop CMOS microelectronics hand calculations to verify a design, before performing the computer simulation and layout of CMOS analog integrated circuits. The full methodology is described to develop designs of passive components, as well as CMOS amplifiers. The methods are used in teaching CMOS microelectronics to students of electronic engineering with industrial partner participation. This paper describes an exhaustive example of a low-voltage operational transconductance amplifier (OTA) design which is used to design an instrumentation amplifier. Finally, a test is performed using this instrumentation amplifier to implement a front-end signal conditioning device for CMOS-MEMS biomedical applications.


Assuntos
Amplificadores Eletrônicos , Semicondutores , Simulação por Computador , Desenho de Equipamento , Humanos , Óxidos
11.
Sensors (Basel) ; 21(20)2021 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-34695970

RESUMO

At the present time, there are major concerns regarding global warming and the possible catastrophic influence of greenhouse gases on climate change has spurred the research community to investigate and develop new gas-sensing methods and devices for remote and continuous sensing. Furthermore, there are a myriad of workplaces, such as petrochemical and pharmacological industries, where reliable remote gas tests are needed so that operatives have a safe working environment. The authors have concentrated their efforts on optical fibre sensing of gases, as we became aware of their increasing range of applications. Optical fibre gas sensors are capable of remote sensing, working in various environments, and have the potential to outperform conventional metal oxide semiconductor (MOS) gas sensors. Researchers are studying a number of configurations and mechanisms to detect specific gases and ways to enhance their performances. Evidence is growing that optical fibre gas sensors are superior in a number of ways, and are likely to replace MOS gas sensors in some application areas. All sensors use a transducer to produce chemical selectivity by means of an overlay coating material that yields a binding reaction. A number of different structural designs have been, and are, under investigation. Examples include tilted Bragg gratings and long period gratings embedded in optical fibres, as well as surface plasmon resonance and intra-cavity absorption. The authors believe that a review of optical fibre gas sensing is now timely and appropriate, as it will assist current researchers and encourage research into new photonic methods and techniques.


Assuntos
Tecnologia de Fibra Óptica , Fibras Ópticas , Gases , Semicondutores , Transdutores
12.
Nano Lett ; 21(19): 8385-8392, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34606292

RESUMO

The microbolometer is the cornerstone device for imaging in the long-wavelength infrared range (LWIR) at room temperature. The state-of-the-art commercial microbolometers usually have a large thermal time constant (TTC) of over 10 ms, limited by their substantial device heat capacity. Moreover, the minimal pixel size of state-of-the-art bolometer is around 10 µm by 10 µm to ensure sufficient power absorption per pixel. Here, we demonstrate an ultrafast silicon nanomembrane microbolometer with a small heat capacity of around 1.9 × 10-11J/K, which allows for its operation at a speed of over 10 kHz, corresponding to a TTC of less than 16 µs. Moreover, a compact diabolo antenna is leveraged for efficient LWIR light absorption, enabling the downscaling of the active area size to 6.2 µm by 6.2 µm. Because of the complementary metal oxide semiconductor (CMOS)-compatible fabrication processes, our demonstration here may lead to a future high-resolution and high-speed LWIR imaging solution.


Assuntos
Semicondutores , Silício , Raios Infravermelhos , Óxidos
13.
Anal Chem ; 93(43): 14425-14431, 2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34672522

RESUMO

As the most important small molecules revealing the origins of life, amino acids (AAs) play essential roles in living organisms and their facile enantiodiscrimination has long been a great challenge for analytical chemists. Inspired by the specific stereomatching effect between biomolecules and AA enantiomers, herein, we first developed a bio-inspired highly sensitive platform based on an extended-gate metal-oxide-semiconductor field-effect-transistor (EG-MOSFET) for highly sensitive AA enantiodiscrimination. Bovine serum albumin (BSA) was self-assembled on deposited Au surfaces to afford the extended gate (EG) sensing unit, and its enantiorecognition ability was initially verified using common electrochemical techniques. The EG was thereafter installed to a MOSFET to build the desired BSA-EG-MOSFET highly sensitive chiral sensing platform, which realized the efficient enantiodiscrimination of essential AAs with high sensitivity, where effective chiral resolution was achieved at the femtomole level to phenylalanine (Phe). Combining molecular docking and circular dichroism spectroscopy, the weak intermolecular interactions between BSA and AAs enantiomers were investigated and the mechanism for signal amplification was proposed. Our results demonstrate that the as-fabricated biosensor has great potential in highly sensitive chiral sensing fields and can also afford a potential tool for biomolecular interaction investigations.


Assuntos
Aminoácidos , Técnicas Biossensoriais , Simulação de Acoplamento Molecular , Óxidos , Semicondutores
14.
Sensors (Basel) ; 21(17)2021 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-34502686

RESUMO

The spread of practical terahertz (THz) systems dedicated to the telecommunication, pharmacy, civil security, or medical markets requires the use of mainstream semiconductor technologies, such as complementary metal-oxide-semiconductor (CMOS) lines. In this paper, we discuss the operation of a CMOS-based free space all-electronic system operating near 250 GHz, exhibiting signal-to-noise ratio (SNR) with 62 dB in the direct detection regime for one Hz equivalent noise bandwidth. It combines the state-of-the-art detector based on CMOS field-effect-transistors (FET) and a harmonic voltage-controlled oscillator (VCO). Three generations of the oscillator circuit are presented, and the performance characterization techniques and their improvement are explained in detail. The manuscript presents different emitter-detector pair operation modalities, including spectroscopy and imaging.


Assuntos
Semicondutores , Silício , Eletrônica , Óxidos , Razão Sinal-Ruído
15.
Chemosphere ; 282: 131137, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34470173

RESUMO

This study investigated biological treatment for two kinds of volatile organic compounds (VOCs)-containing wastewaters collected from wet scrubbers in a semiconductor industry. Batch test results indicated that one wastewater containing highly volatile organic compounds was not suitable for aerated treatment conditions while the other containing much lower volatile organic compounds was suitable for aerobic treatment. Accordingly, two moving bed bioreactors, by adding commercial biocarrier BioNET, were operated under aerobic and anoxic conditions for treating low volatility wastewater (LVW) and high volatility wastewater (HVW), respectively. During 280 days of operation, the aerobic LVW bioreactor attained the highest chemical oxygen demand (COD) removal rate of 98.9 mg-COD/L/h with 81% of COD removal efficiency at hydraulic retention time (HRT) of 1 day. The anoxic HVW bioreactor performed above 80% of COD removal efficiency with the highest COD removal rate of 16.5 mg-COD/L/h at HRT of 2 days after 380 days of operation. The specific COD removal rates at different initial substrate-to-biomass (S0/X0) ratios, using either suspended sludge or microorganisms attached onto BioNET from both bioreactors, followed the Monod-type kinetics, while the half-saturation coefficients were generally higher for the microorganisms onto BioNET due presumably to relatively poor mass transfer efficiency. Based on the results of microbial community analysis using the next generation sequencing technique, the dominant communities of suspended sludge and BioNET, including nitrifiers, denitrifiers, and degraders for polycyclic aromatic hydrocarbons, were similar in the corresponded bioreactors, but microbial community shifts were observed with increased organic loadings.


Assuntos
Compostos Orgânicos Voláteis , Águas Residuárias , Reatores Biológicos , Semicondutores , Esgotos
16.
ACS Appl Mater Interfaces ; 13(36): 43696-43707, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34470205

RESUMO

Graphene is a two-dimensional semiconducting material whose application for diagnostics has been a real game-changer in terms of sensitivity and response time, variables of paramount importance to stop the COVID-19 spreading. Nevertheless, strategies for the modification of docking recognition and antifouling elements to obtain covalent-like stability without the disruption of the graphene band structure are still needed. In this work, we conducted surface engineering of graphene through heterofunctional supramolecular-covalent scaffolds based on vinylsulfonated-polyamines (PA-VS). In these scaffolds, one side binds graphene through multivalent π-π interactions with pyrene groups, and the other side presents vinylsulfonated pending groups that can be used for covalent binding. The construction of PA-VS scaffolds was demonstrated by spectroscopic ellipsometry, Raman spectroscopy, and contact angle measurements. The covalent binding of -SH, -NH2, or -OH groups was confirmed, and it evidenced great chemical versatility. After field-effect studies, we found that the PA-VS-based scaffolds do not disrupt the semiconducting properties of graphene. Moreover, the scaffolds were covalently modified with poly(ethylene glycol) (PEG), which improved the resistance to nonspecific proteins by almost 7-fold compared to the widely used PEG-monopyrene approach. The attachment of recognition elements to PA-VS was optimized for concanavalin A (ConA), a model lectin with a high affinity to glycans. Lastly, the platform was implemented for the rapid, sensitive, and regenerable recognition of SARS-CoV-2 spike protein and human ferritin in lab-made samples. Those two are the target molecules of major importance for the rapid detection and monitoring of COVID-19-positive patients. For that purpose, monoclonal antibodies (mAbs) were bound to the scaffolds, resulting in a surface coverage of 436 ± 30 ng/cm2. KD affinity constants of 48.4 and 2.54 nM were obtained by surface plasmon resonance (SPR) spectroscopy for SARS-CoV-2 spike protein and human ferritin binding on these supramolecular scaffolds, respectively.


Assuntos
Biomarcadores/análise , COVID-19/diagnóstico , Grafite/química , Imunoensaio/métodos , Glicoproteína da Espícula de Coronavírus/análise , Anticorpos Monoclonais/química , Anticorpos Monoclonais/imunologia , Etilenos/química , Ferritinas/imunologia , Ferritinas/metabolismo , Humanos , Sistemas Automatizados de Assistência Junto ao Leito , Poliaminas/química , Polietilenoglicóis/química , Pirenos/química , Teoria Quântica , SARS-CoV-2/isolamento & purificação , SARS-CoV-2/metabolismo , Semicondutores , Glicoproteína da Espícula de Coronavírus/imunologia , Ácidos Sulfônicos/química , Ressonância de Plasmônio de Superfície
17.
Sensors (Basel) ; 21(18)2021 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-34577368

RESUMO

The on-chip integration of multiple biochemical sensors based on field-effect electrolyte-insulator-semiconductor capacitors (EISCAP) is challenging due to technological difficulties in realization of electrically isolated EISCAPs on the same Si chip. In this work, we present a new simple design for an array of on-chip integrated, individually electrically addressable EISCAPs with an additional control gate (CG-EISCAP). The existence of the CG enables an addressable activation or deactivation of on-chip integrated individual CG-EISCAPs by simple electrical switching the CG of each sensor in various setups, and makes the new design capable for multianalyte detection without cross-talk effects between the sensors in the array. The new designed CG-EISCAP chip was modelled in so-called floating/short-circuited and floating/capacitively-coupled setups, and the corresponding electrical equivalent circuits were developed. In addition, the capacitance-voltage curves of the CG-EISCAP chip in different setups were simulated and compared with that of a single EISCAP sensor. Moreover, the sensitivity of the CG-EISCAP chip to surface potential changes induced by biochemical reactions was simulated and an impact of different parameters, such as gate voltage, insulator thickness and doping concentration in Si, on the sensitivity has been discussed.


Assuntos
Eletrólitos , Semicondutores , Capacitância Elétrica
18.
J Synchrotron Radiat ; 28(Pt 5): 1444-1454, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34475292

RESUMO

Spatially fractionated ultra-high-dose-rate beams used during microbeam radiation therapy (MRT) have been shown to increase the differential response between normal and tumour tissue. Quality assurance of MRT requires a dosimeter that possesses tissue equivalence, high radiation tolerance and spatial resolution. This is currently an unsolved challenge. This work explored the use of a 500 nm thick organic semiconductor for MRT dosimetry on the Imaging and Medical Beamline at the Australian Synchrotron. Three beam filters were used to irradiate the device with peak energies of 48, 76 and 88 keV with respective dose rates of 3668, 500 and 209 Gy s-1. The response of the device stabilized to 30% efficiency after an irradiation dose of 30 kGy, with a 0.5% variation at doses of 35 kGy and higher. The calibration factor after pre-irradiation was determined to be 1.02 ±â€…0.005 µGy per count across all three X-ray energy spectra, demonstrating the unique advantage of using tissue-equivalent materials for dosimetry. The percentage depth dose curve was within ±5% of the PTW microDiamond detector. The broad beam was fractionated into 50 microbeams (50 µm FHWM and 400 µm centre-to-centre distance). For each beam filter, the FWHMs of all 50 microbeams were measured to be 51 ±â€…1.4, 53 ±â€…1.4 and 69 ±â€…1.9 µm, for the highest to lowest dose rate, respectively. The variation in response suggested the photodetector possessed dose-rate dependence. However, its ability to reconstruct the microbeam profile was affected by the presence of additional dose peaks adjacent to the one generated by the X-ray microbeam. Geant4 simulations proved that the additional peaks were due to optical photons generated in the barrier film coupled to the sensitive volume. The simulations also confirmed that the amplitude of the additional peak in comparison with the microbeam decreased for spectra with lower peak energies, as observed in the experimental data. The material packaging can be optimized during fabrication by solution processing onto a flexible substrate with a non-fluorescent barrier film. With these improvements, organic photodetectors show promising prospects as a cost-effective high spatial resolution tissue-equivalent flexible dosimeter for synchrotron radiation fields.


Assuntos
Radioterapia/instrumentação , Semicondutores , Fracionamento da Dose de Radiação , Desenho de Equipamento , Dosímetros de Radiação , Dosagem Radioterapêutica , Síncrotrons , Raios X
19.
Nano Lett ; 21(19): 8190-8196, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34551246

RESUMO

The spin-dependent propagation of electrons in helical nanowires is investigated. We show that the interplay of spin angular momentum and nanowire chirality, under spin-orbit interaction, lifts the symmetry between left and right propagating electrons, giving rise to a velocity asymmetry. The study is based on a microscopic tight-binding model that takes into account the spin-orbit interaction. The continuity equation for the spin-dependent probability density is derived, including the spin nonconserving terms, and quantum dynamics calculations are performed to obtain the electron propagation dynamics. The calculations are applied to the inorganic double-helix SnIP, a quasi-1D material that constitutes a semiconductor with a band gap of ∼1.9 eV. The results, nevertheless, have general validity due to symmetry considerations. The relation of the propagation velocity asymmetry with the phenomena ascribed to the chiral-induced spin selectivity effect is examined.


Assuntos
Elétrons , Semicondutores , Movimento (Física)
20.
Nano Lett ; 21(19): 8409-8417, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34591493

RESUMO

The dielectric screening from the disordered media surrounding atomically thin transition metal dichalcogenides (TMDs) monolayers modifies the effective defect energy levels and thereby the transport and energy dynamics of excitons. In this work, we study this effect in WSe2 monolayers for different combinations of surrounding dielectric media. Specifically, we study the source of the anomalous diffusion of excitons in the WSe2 monolayer and attribute the anomaly to the modification of the energy distribution of defect states in different disordered dielectric environments. We use this insight to manipulate exciton transport by engineering the dielectric environment using a graphene/hexagonal boron nitride (h-BN) moiré superlattice. Finally, we observe that the effect of dielectric disorder is even more significant at high excitation fluences, contributing to the nonequilibrium phonon drag effect. These results provide an important step toward achieving control over the exciton energy transport for next-generation opto-excitonic devices.


Assuntos
Grafite , Elementos de Transição , Difusão , Fônons , Semicondutores
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