We show theoretically that when a semiconductor quantum dot and metallic nanoparticle system interacts with a laser field, quantum coherence can introduce a new landscape for the dynamics of Forster resonance energy transfer (FRET). We predict adsorption of biological molecules to such a hybrid system can trigger dramatic changes in the way energy is transferred, blocking FRET while the distance between the quantum dot and metallic nanoparticle (R) and other structural specifications remain unchanged. We study the impact of variation of R on the FRET rate in the presence of quantum coherence and its ultrafast decay, offering a characteristically different dependency than the standard 1/R6. Application of the results for quantum nanosensors is discussed.
It is well known that irradiation of colloidal quantum dots can dramatically enhance their emission efficiencies, leading to so-called photoinduced fluorescence enhancement (PFE). This process is the result of the photochemical and photophysical properties of quantum dots and the way they interact with the environment in the presence of light. It has been shown that such properties can be changed significantly using metal oxides. Using spectroscopic techniques, in this paper we investigate emission of different types of quantum dots (with and without shell) in the presence of metal oxides with opposing effects. We observed significant increase of PFE when quantum dots are deposited on about one nanometer of aluminum oxide, suggesting such oxide can profoundly increase quantum yield of such quantum dots. On the other hand, copper oxide can lead to significant suppression of emission of quantum dots, making them nearly completely dark instantly.
The potential for buildup of formaldehyde in closed space environments poses a direct health hazard to personnel. The
National Aeronautic Space Agency (NASA) has established a maximum permitted concentration of 0.04 ppm for 7 to
180 days for all space craft. Early detection is critical to ensure that formaldehyde levels do not accumulate above these
limits. New sensor technologies are needed to enable real time, in situ detection in a compact and reusable form factor.
Addressing this need, research into the use of reactive fluorescent dyes which reversibly bind to formaldehyde (liquid or
gas) has been conducted to support the development of a formaldehyde sensor. In the presence of formaldehyde the
dyes' characteristic fluorescence peaks shift providing the basis for an optical detection. Dye responses to formaldehyde
exposure were characterized; demonstrating the optical detection of formaldehyde in under 10 seconds and down to
concentrations of 0.5 ppm. To incorporate the dye in an optical sensor device requires a means of containing and
manipulating the dye. Multiple form factors using two dissimilar substrates were considered to determine a suitable
configuration. A prototype sensor was demonstrated and considerations for a fieldable sensor were presented. This
research provides a necessary first step toward the development of a compact, reusable, real time optical formaldehyde
sensor suitable for use in the U.S. space program.
The roles of sensor systems in the current and Future Force have necessarily affected an evolution of the requirements for the distribution and management of sensor data. No longer do the closed, stove pipe solutions of the past come close to meeting the interoperability needs. New sensor technologies and deployment concepts have pushed sensors into the network centric world and have simultaneously presented a requirement for joint standard digital communications capable of dynamic discovery of nodes on the network, runtime reconfiguration of sensing devices, multi-connection support, and sensor to sensor direct communications.
To meet these evolving sensor system data management, interface and communications requirements, a team of Government and defense contractors has collaborated to define a component-wise sensor interface architecture and messaging standard. The core component of this sensor interoperability architecture is the proposed Sensor Data Link (SDL) messaging standard. SDL provides a flexible framework of joint standard data representations, messages, and common processes for current and Future Force sensors.