senzor detectie – Baza de Date

Cercetătorii detectează detectarea gazului la temperatura camerei(Researchers greenlight gas detection at room temperature)

Cercetatorii rusi au dezvoltat un mecanism pentru detectarea hidrogenului molecular folosind lumina verde pentru iluminarea unui senzor compozit nanocristalin bazat pe oxizi de zinc si indiu. Pentru prima dată, acest lucru permite un senzor de gaz care funcționează la temperatura camerei.Astfel de senzori pot fi utilizați pentru a analiza calitatea aerului în aer liber și în spații închise

Posted: Oct 25, 2017
Researchers greenlight gas detection at room temperature (Nanowerk News) Russian researchers have developed a mechanism for detecting molecular hydrogen using green light to illuminate a nanocrystalline composite sensor based on zinc and indium oxides. For the first time, this enables a gas sensor operating at room temperature. The paper was published in the journal Scientific Reports („Green light activated hydrogen sensing of nanocrystalline composite ZnO-In2O3 films at room temperature”).
Multisensor arrays for determining gas mixture composition are currently being developed. These are monitoring systems incorporating multiple sensors that target individual gases. Such sensors can be used to analyze air quality both outdoors and in closed spaces. Tracking atmospheric pollution remains a vital concern for many developed countries. Because residential communities tend to cluster around industrial areas, it is necessary to have a mechanism in place for controlling harmful emissions from plants and factories.
Besides that, air composition measurements are required at nuclear power plants, on submarines and space stations, and at other facilities where access to fresh air is not immediately available: If the concentration of carbon dioxide increases or a toxic substance leaks into the ventilation system, this might put the lives of personnel at risk.
Commercial gas mixtures such as gas fuels also need precise composition monitoring. Among them is hydrogen. Used as gas fuel, it could conceivably replace hydrocarbons. It is a clean fuel that releases nothing but water vapor when burnt. In addition, the efficiency of burning hydrogen is 10 to 20 percent higher than that of hydrocarbons. Some car manufacturers have already started phasing in hydrogen seeing it as a fuel of the future. And yet the Hindenburg airship disaster is a sad reminder of how dangerous hydrogen can be.
Until recently, gas sensors based on nanocrystalline metal oxides had operating temperatures between 300 and 500 degrees Celsius. This made them unsafe for the detection of explosive or combustible substances. Moreover, to maintain these high temperatures, a lot of power is required, making it impossible to embed such gas sensors into the circuit boards of portable devices.
To solve this problem, Professor Leonid Trakhtenberg of MIPT; Pavel Kashkarov, director of the Institute of Nano-, Bio-, Information, Cognitive and Socio-Humanistic Science and Technology; Alexander Ilin and Pavel Forsh from Lomonosov Moscow State University; and their colleagues from Semenov Institute of Chemical Physics proposed sensors capable of operating at room temperature. Their new nanocomposite sensors are based on zinc and indium oxides, and their efficiency is maximized by green light illumination. The proposed device could be used to detect combustible, explosive, or poisonous substances in the atmosphere even at low concentrations.
“The mechanism consists in the light-induced transition of the nanocrystalline sensor components into a nonequilibrium state and the resulting change in the photoconductivity of the sensor interacting with molecular hydrogen. This effect is linked with the dependence of photoconductivity on the nonequilibrium charge carrier recombination rate,” explains Maria Ikim, a doctoral student at the Laboratory of Functional Nanocomposites of Semenov Institute of Chemical Physics of the Russian Academy of Sciences.

Photoconductivity (curve 1) and electrical conductivity (curve 2) of a composite film made of zinc and indium oxides in a 1-to-9 ratio by weight under periodic exposure to air containing hydrogen. Orange marks the scope of sensor response.
“The detectors that we have developed differ from the conventional semiconductor sensors in that they operate at room temperature. This eliminates the danger of combustion or explosion, when flammable or explosive substances are involved,” says Leonid Trakhtenberg of the Department of Chemical Physics, MIPT, who holds an ScD in physics and mathematics. “Most papers on sensor photoactivation discuss the effects of ultraviolet light on sensors and focus on the detection of oxidizing gases. But the efficiency of ultraviolet light diodes is low, while their cost is far greater than that of their counterparts emitting in the visible part of the spectrum. By working with hydrogen, we explore the possibilities of the detection of reducing gases.”
The paper reported in this story proposes a novel mechanism of sensor response photoactivation, which is illustrated by the image above. It accounts for the transition of charge carriers into a nonequilibrium state. The process involved is universal: It can be used to interpret sensing results in both oxidizing and reducing gases.
The sensors proposed by the authors could be used to monitor atmospheric air composition and analyze the chemical makeup of gases used in industrial processes. Although the study focuses on gases, the same sensors could be modified to target liquids.

Source: Moscow Institute of Physics and Technology

Nanosenzorul senzitiv se trezește numai în prezența unui semnal de interes (Dormant nanosensor awakens only in the presence of a signal of interest )

Construiți un senzor minuscul care detectează o semnătură de lungimi de undă în infraroșu (IR) caracteristice unei conducte de esapament fierbinți, unui foc de lemn sau chiar unei ființe umane. Proiectați senzorul astfel încât acesta să rămână în stare latentă și nesupravegheată, dar întotdeauna în stare de alertă, chiar și ani de zile, fără a atrage energia bateriei. Și construiți senzorul astfel încât actul de detecție în sine poate iniția emiterea unui semnal care avertizează războinicii, pompierii sau alții că a fost detectat un „semnal de interes”. Este doar o tehnologie de inteligență, recunoaștere și supraveghere (ISR), care poate spori gradul de conștientizare a situației, reducând în același timp necesitatea unor misiuni de întreținere potențial periculoase pentru înlocuirea bateriilor de descărcare. „Ceea ce este cu adevărat interesant în ceea ce privește tehnologia Northeastern IR sensor este că, spre deosebire de senzorii convenționali, acesta consumă zero putere de stand-by atunci când lungimile de undă IR care trebuie detectate nu sunt prezente”, a declarat Troy Olsson, manager al programului N-ZERO în DARPA’s Microsystems Technology Office. „Când aceste lungimi de undă IR sunt prezente și afectează senzorul IR al echipei Northeastern, energia din sursa IR încălzește elementele senzoriale care, la rândul lor, determină mișcarea fizică a componentelor senzorilor cheie. Aceste mișcări au ca rezultat închiderea mecanică a elementelor de circuit deschis, în alt mod, ceea ce duce la semnalele de detectare a semnăturii IR. „

Posted: Sep 12, 2017
Dormant nanosensor awakens only in the presence of a signal of interest (Nanowerk News) Here’s your task. Build a tiny sensor that detects a signature of infrared (IR) wavelengths characteristic of a hot tailpipe, a wood fire, or perhaps even a human being. Design the sensor so that it can remain dormant and unattended but always alert, even for years, without drawing on battery power. And build the sensor so that the act of detection itself can initiate the emission of a signal that alerts warfighters, firefighters, or others that a “signal-of-interest” has been detected. It’s just the sort of intelligence, reconnaissance, and surveillance (ISR) technology that can increase situational awareness while minimizing the need for potentially dangerous maintenance missions to replace run-down batteries.
Reporting in the journal Nature Nanotechnology („Zero Power Infrared Digitizers Based on Plasmonically-enhanced Micromechanical Photoswitches”), a research team at Northeastern University, led by Electrical and Computer Engineering Associate Professor Matteo Rinaldi, reports pulling off this tall order of DARPA’s Near Zero Power RF and Sensor Operation (N-ZERO) program with a device the Boston team refers to as a “plasmonically-enhanced micromechanical photoswitch.”

The micrograph features the multiple, wavelength-specific sensor patches that enable this N-ZERO device to capture infrared signatures of specific heat-emitting sources. (Image: DARPA)
“What is really interesting about the Northeastern IR sensor technology is that, unlike conventional sensors, it consumes zero stand-by power when the IR wavelengths to be detected are not present,” said Troy Olsson, manager of the N-ZERO Program in DARPA’s Microsystems Technology Office. “When those IR wavelengths are present and impinge on the Northeastern team’s IR sensor, the energy from the IR source heats the sensing elements which, in turn, causes physical movement of key sensor components. These motions result in the mechanical closing of otherwise open circuit elements, thereby leading to signals that the target IR signature has been detected.”
The sensor is a showcase of clever physics and engineering, including a grid of nanoscale patches whose specific dimensions limit them to absorb only particular IR wavelengths. “The charge-based excitations, called plasmons (that can be thought of somewhat like ripples on the surface of water), are highly localized below the nanoscale patches and effectively trap specific wavelengths of light into the ultra-thin structure, inducing a relatively large and swift spike in its temperature,” Rinaldi explained. These temperature spikes, in turn, lead to an upstream sequence of events that culminates in circuit-completing deformations of other parts of the sensor.
“The technology features multiple sensing elements—each tuned to absorb a specific IR wavelength,” Olsson noted. “Together, these combine into complex logic circuits capable of analyzing IR spectrums, which opens the way for these sensors to not only detect IR energy in the environment but to specify if that energy derives from a fire, vehicle, person or some other IR source.”
Consider the identification of vehicles from their IR emissions. Engines that burn gasoline or diesel fuels emit specific compounds in their exhaust gases. Among these compounds are CO2, CO, H2O, various oxides of nitrogen and sulfur (NOx and SOx, respectively), and hydrocarbons such as methane. “As a result, the infrared emission spectra of the heated tailpipe gases coming out of vehicles such as trucks, cars or aircraft can by themselves act as a signature specific to a vehicle type,” explained Zhenyun Qian, who has been working with Rinaldi and other research team members on the N-ZERO program.
A primary goal of the N-ZERO program is to develop fundamental technologies that open the way to new and more capable sensor systems relevant to national security. The NU team points out in its Nature Nanotechnology paper that the same technology could become important over the coming years as the Internet of Things expands to include hundreds of billions of devices, ranging from cars, to appliances, to remotely deployed sensors. “The capability of consuming power only when useful information is present will result in nearly unlimited duration of operation for unattended sensors deployed to detect infrequent but time-critical events, with a groundbreaking impact on the proliferation of the Internet of Things,” the Northeastern researchers predict in their paper.

Source: DARPA

Sistemul de cipuri nanofotonice măsoară lumina de la o singură celulă bacteriană pentru a permite detectarea chimică portabilă ( Nanophotonic chip system measures light from a single bacterial cell to enable portable chemical detection )

Noul sistem, descris în jurnalul Nano Letters ( „Nanoscale Plasmonic V-Groove Waveguides pentru interogarea celulelor bacteriene fluorescente unice” ), deschide calea pentru un sistem eficient și portabil on-chip pentru diverse aplicații de detectare pe bază de celule, cum ar fi Ca și detectarea substanțelor chimice în timp real.
construirea unei rețele de ghiduri de undă, diversificarea sistemului pentru a încorpora diferite tipuri de senzori bacterieni pentru detectarea diferitelor analitări biologice sau chimice.

Posted: Aug 30, 2017
Nanophotonic chip system measures light from a single bacterial cell to enable portable chemical detection (Nanowerk News) Researchers at the Hebrew University of Jerusalem have created a nanophotonic chip system using lasers and bacteria to observe fluorescence emitted from a single bacterial cell. To fix the bacteria in place and to route light toward individual bacterial cells, they used V-groove-shaped plasmonic waveguides, tiny aluminum-coated rods only tens of nanometers in diameter.
The novel system, described in the journal Nano Letters („Nanoscale Plasmonic V-Groove Waveguides for the Interrogation of Single Fluorescent Bacterial Cells”), paves the way for an efficient and portable on-chip system for diverse cell-based sensing applications, such as detecting chemicals in real-time.

Top: SEM image of bacteria deposited inside a V-groove waveguide. Bottom: napshot of bacterial fluorescence excitation via free space beam and the coupling of the fluorescence to the waveguide. The two nanocouplers at the end of the waveguide emit about the same intensity of light because they are roughly the same distance from the bacterium. (© ACS)
The field of on-chip photonic devices for biological and chemical sensing applications presents many powerful alternatives to conventional analytical techniques for applications ranging from “lab on a chip” to environmental monitoring. However, these sensing schemes rely mainly on off-chip detection and require a cumbersome apparatus, even when measuring only single cells.
The Hebrew University team looked for ways to integrate all system components, including light sources and detectors, on-chip at the nanoscale. This would result in a lab-on-chip system that is small, portable and can perform sensing in real-time.
To achieve this, they molecularly engineered live bacteria that emit a fluorescent signal in the presence of target compounds. They paired these on-chip with a nanoscale waveguide, which not only served the purpose of guiding light, but also allowed mechanical trapping of individual bacteria within the V-groove.
In three different illumination conditions, they experimentally demonstrated the interrogation of an individualEscherichia coli bacterial cell using a nanoscale plasmonic V-groove waveguide. First, they measured the light emitted from a bacterium flowing on top of the nanocoupler in a liquid environment by allowing the fluorescence from the bacterium to be coupled directly into the waveguide through the nanocoupler. Next, a bacterium was mechanically trapped within the V groove waveguide and was excited by laser directly either from the top or through the nanocoupler. In all cases, significant fluorescence was collected from the output nano coupler into the detector.
The system worked well both in wet environments, where the bacteria are flowing on top of the waveguide, and in dry conditions, where the bacteria are trapped within the waveguide.
The research was led by Prof. Uriel Levy, Director of The Harvey M. Krueger Family Center for Nanoscience and Nanotechnology at the Hebrew University in collaboration with Prof. Shimshon Belkin, at the Hebrew University’s Alexander Silberman Institute of Life Sciences, who genetically engineered the bacterial sensors, and Prof. Anders Kristensen from the Danish Technical University, who was in charge of fabricating the V-groove waveguides. Prof. Levy is the Eric Samson Chair in Applied Science and Technology, and Prof. Belkin is the Ministry of Labor and Social Welfare Chair in Industrial Hygiene, at the Hebrew University.
Unlike the more traditional plasmonic waveguides consisting of either silver or gold, the choice of aluminum was instrumental for being able to guide the fluorescent light emitted from the bacteria all the way to the output nanocoupler. Furthermore, the waveguide dimensions allow for efficient mechanical trapping of the bacteria and the multimode characteristics may become instrumental in gathering more information, e.g., on the specific position and orientation of the bacteria.
The results provide a clear indication of the feasibility of constructing a hybrid bioplasmonic system using live cells. Future work will include the construction of waveguide network, diversifying the system to incorporate different types of bacterial sensors for the detection of various biological or chemical analytes.