19 research outputs found
A SiON Microring Resonator-Based Platform for Biosensing at 850 nm
No full textn this paper, we report on the design, fabrication, and characterization of a photonic circuit for biosensing applications. Silicon oxynitride with a bulk refractive index of 1.66 is the core-layer material. The photonic circuit is optimized for a wavelength of ~850 nm, which allows on-chip integration of the light source via cost effective vertical-cavity surface-emitting lasers and of the detector by using standard silicon photodetectors. Design as well as fabrication processes are explained in details. The best characteristics for the single optical components in the photonic circuit are: for single-mode channel waveguides with dimensions of 350 nm × 950 nm; propagation losses of 0.8 dB/cm; bending losses of 0.1 dB/90°-bend (radius of curvature 100 μm); 49/51 splitting ratio for 3-dB power splitters (directional couplers); quality factors up to 1.3 × 105 for microring resonators. Volumetric sensing yields a bulk sensitivity of 80 nm/RIU and a limit of detection of 3 × 10-6 RIU. Therefore, SiON-based photonic circuits represent a reliable material platform for biosensing in the short-wave near infrared region
Design and Optimization of SiON Ring Resonator-Based Biosensors for Aflatoxin M1 Detection
No full textIn this article, we designed and studied silicon oxynitride (SiON) microring-based photonic structures for biosensing applications. We designed waveguides, directional couplers, and racetrack resonators in order to measure refractive index changes smaller than 10−6 refractive index units (RIU). We tested various samples with different SiON refractive indexes as well as the waveguide dimensions for selecting the sensor with the best performance. Propagation losses and bending losses have been measured on test structures, along with a complete characterization of the resonator’s performances. Sensitivities and limit of detection (LOD) were also measured using glucose-water solutions and compared with expected results from simulations. Finally, we functionalized the resonator and performed sensing experiments with Aflatoxin M1 (AFM1). We were able to detect the binding of aflatoxin for concentrations as low as 12.5 nm. The results open up the path for designing cost-effective biosensors for a fast and reliable sensitive analysis of AFM1 in milk
Sensitivity and Limit of Detection of biosensors based on ring resonators
No full textIn this work, we present a study of the Sensitivity (S) and Limit of Detection (LOD) of microring based photonic biosensors as a function of the waveguide composition and dimensions. The target is Aflatoxin, which is a toxin of major concern for south Europe dairy industry. The sensing device is based on an array of multiple SiON microring resonators, fiber-coupled to both an 850 nm VCSEL and a silicon photodetectors, packaged with a microfluidic circuit. Volumetric sensing with glucose–water solutions of various concentrations yields a best sensitivity of 112 nm/RIU. To link these results to the Limit of Detection of the sensors, we also measured the noise of our experimental readout system and then calculated the LOD of our sensors. We found a best value of LOD of 1.6 × 10−6 RIU (referred to volumetric sensing). Finally, we detected Aflatoxin in solutions of various concentrations (down to 1.58 nM) by functionalized sensors. The functionalization is based on a wet silanization and specific DNA-aptamer binding on the chip. Reproducibility and re-usability of the sensor are investigated by several chemical treatments. Optimum procedure allows multiple sequential measurements with a good endurance. This work was supported by the FP7 EU project “Symphony” (Grant agreement no.: 610580). Keywords: Biosensor, Whispering Gallery Mode, Ring resonator, Aflatoxin, Limit of Detection, Sensitivit
Aptamer- and Fab’- Functionalized Microring Resonators for Aflatoxin M1 Detection
No full textSilicon oxynitride (SiON) microring resonators are used to develop a biosensor device to detect Aflatoxin M1 (AFM1), a carcinogenic mycotoxin present in milk. Two different surface functionalization strategies are tested to realize an affinity biosensing device. Both strategies are based on the formation of a silane surface layer able to bind either specific DNA-aptamers or antigen binding fragments (Fab'). The sensing device consists of an array of four SiON microring resonators, fiber-coupled to a vertical cavity surface emitting laser operating at 850 nm. Detection is realized with off-chip silicon photodetectors. With both functionalizations, we demonstrate a specific detection of AFM1 in buffer, while the nonspecific detection of Ochratoxin is not occurring. Repeatability and reproducibility of both functionalization strategies are discussed
An integrated optical biosensor platform
No full textA tiny, low-cost evanescent-field biosensor chip with a directly integrated optical detector enables carcinogenic contaminant detection and shows promise for point-of-use application
Silicon-based photonic integrated circuit for label-free biosensing
No full textSilicon-based Photonic Integrated Circuit (PIC) is a device that integrates several optical components using the mature semiconductor technology platform, developed through years for the needs of electronic integrated circuits. In recent years, silicon PICs have been demonstrated as a powerful platform for biosensing systems - devices which play an omnipresent role in such essential life aspects as health care, environmental monitoring, food safety, etc. The growing importance of silicon photonics technologies for biosensor development consists in the possibility of realization compact and simple-to-use instruments, socalled
Lab-On-a-Chip (LOC), enabling rapid point-of-care analysis. This dissertation was carried out within the European project Symphony (grant number 610580), dedicated to the development of a portable sensor instrument for timely detection of highly carcinogenic compound Aflatoxin M1 in milk. The main objective of this Thesis is a development of one of the key element of such system - a photonic chip for label-free biosensing. The PIC operates at the short-wave near-infrared wavelength range (at 850 nm) and integrates an array of silicon oxynitride microring resonators for multiplexed analysis of the samples in aqueous ambient. An innovative technology is developed for monolithic
on-chip integration of a low-cost silicon photodetector, used to monitor the sensor response. The theoretical background includes the basics of microring resonators, the optical label-free biosensing principles and the fundamentals of photodetectors. The design of photonic circuit elements and different numerical models, used for the device simulations, are discussed in details. A great part of the work is dedicated to the optimization of the fabrication process, which is comprehensively explained and illustrated in the thesis. A complete characterization of the realized optical components is presented, including the study of typical performance parameters of waveguides, splitters and microring resonators. To evaluate the sensors functionality, the volumetric sensing experiments are performed using the home-made microfluidic module. The results reveal a high sensor performance, comparable with the state-of-the-art: the devices are able to sense the changes in the refractive index of solution with the limit of detection down to 2*10^-6 refractive index units.
Finally, the characterization of the on-chip integrated PIN photodiodes is presented. The detectors demonstrate the very encouraging results, showing a good responsivity at 850 nm and a capability to efficiently monitor the response of the biosensor array. The successful integration of silicon photodetectors on the highly-sensitive sensor chip can permit the realization of tiny, robust and cost-effective optical biosensors, which gives an important contribution towards the simplification of development of LOC devices
Shallow Nitrogen Vacancy Color Centers in Diamond by Ion Implantation
No full textRecent advancements in quantum technologies are fueled by the ability to engineer materials with specific quantum properties, enabling various applications. The nitrogen-vacancy (NV) center in diamond is a key system for nanoscale sensors, capable of detecting weak magnetic fields with nanotesla-range sensitivity. To achieve high spatial resolution and sensitivity, NV centers must be placed near the diamond surface. This study investigates the creation of NV defects in a pure chemical vapor deposition (CVD) diamond single crystal via broad-beam ion implantation. The implantations are performed through thin (100 nm) SiO2 layers deposited by plasma-enhanced CVD (PECVD). Both normal and oblique ion beam incidences are used, with the oblique incidence chosen to reduce the nitrogen ion penetration depth. Simulations show a subsurface NV center distribution, with the highest concentration near the surface; the expected trends are confirmed by angle-resolved X-ray photoelectron spectroscopy (ARXPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). This distribution extends to a depth of 30 nm. By adjusting the ion beam incidence angle, NV center density can be modulated. This work contributes to optimizing the fabrication process for shallow color centers through ion implantation using a screening layer
The Concept of Information Asymmetry as a Theoretical Substantiation of the Phenomenon of Public Non-Financial Reporting
No full textThe global trend of widespread of public non-financial reporting makes the researchers face the task of finding its scientific basis. A unified theoretical and methodological basis of the concept of public non-financial reporting can be able to form the system of categories, laws, postulates and allow to implement effectively the processes of norm-setting, standardization and harmonization of public non-financial reporting with financial reporting. The purpose of the article is to provide the rationale for the choice of concept of information asymmetry as a fundamental theoretical basis to justify the phenomenon of public non-financial reporting. In the study the author applied the following research methods: analysis, synthesis, induction, deduction, comparison, generalization, and a systems approach. The article provides the results of analysis of extension of public non-financial reporting and identification of the problems of its application in Russian firms. The author systematizes the theoretical concepts be able to explain a phenomenon of public non-financial reporting: concept of sustainable development, the stakeholder theory, the doctrine of fair contracts. The author also demonstrates that the concept of information asymmetry is unifying for all of them and can be used to explain the voluntary adoption of obligations for additional disclosure of non-financial measurers by business. There is a need for a further scientific discussion of ideas about the implementation of public non-financial reporting as a prescriptive institutional or voluntary signaling mechanism, problem of its standardization, the counteract unfair usage of non-financial reporting to strengthen the negative effects of information asymmetry and the reallocation of market goods
Теория учета: современные проблемы и структурно-логическаямодель развития
No full textIntroduction, Purpose. The current stage of development in accounting is characterized by the methodological fragmentation of accounting theory, poor link between accounting theory and the development of social sciences, inability of accounting to cope with challenges of modern economy. These may be a reason for denial of scientific foundations of accounting theory. The purpose of the article is to provide a systematic analysis of the contemporary academic papers devoted to the problems of the development of accounting theory and methodology of accounting in order to formulate a structural-logical model for the development of a level of particular theoretical schemes of accounting. Methods. In the study the author applied the following research methods: analysis, synthesis, induction, deduction, comparison, generalization, and a systems approach. Results. The article provides the results of analysis and systemization of modern problems in accounting theory. The author considers the transformation peculiarities of methodology of accounting as a social and applied science, makes a proposal about how to organize research in the field of accounting theory in accordance with the Academician V. Stepin concept of scientific knowledge organization and formulates a structural-logical model of development of accounting theory concepts as a level of particular theoretical schemes. Discussions. There is a need for a further scientific discussion of ideas about the types of accounting as particular theoretical schemes based, on the one hand, on accounting theory, and on judgments and postulates taken from related fields of social sciences, on the other hand
DEFINING THE SUBJECT AND OBJECTS OF MANAGEMENT ACCOUNTING IN THE CONTEXT OF ACCOUNTING THEORY DEVELOPMENT
No full textThe current stage of management accounting development is characterized by the lack of balance between its theory and practical applications. One of the key features of this process is that management accounting theory along with its development in the context of the accounting theory and related science is not researched deep enough. The purpose of the article is to define the subject of the management accounting and its objects through the development of accounting theory. In the study the following research methods were used: analysis, synthesis, induction, deduction, comparison, generalization, and a system approach. The author studies the evolution of capital as a subject of accounting theory, considers a modern approach to capital as an object of integratedreporting, defines the subject of management accounting. The article proves that management accounting is a research direction of accounting theory as a science of higher level, provides the classification of management accounting objects based on the forms of capital and the way they are related to the state and changes in capital. This classification can be used to make charts of accounts for management accounting, based on the forms and transformations of capital in the system of double-entry or triple-entry bookkeeping
