This critical review is focused on examples reported from 1947 to 2010 related to the design of chromo-fluorogenic chemosensors and reagents for explosives (141 references).

/pdf/optical-chemosensors-and-reagents-to-detect-explosives-50tyjzolpv.pdf

Optical chemosensors and reagents to detect explosives

Electric field poled organic electro-optic materials: state of the art and future prospects.

Polymer networks possessing reversible covalent cross-links constitute a novel material class with the capacity for adapting to an externally applied stimulus. These covalent adaptable networks (CANs) represent a trend in polymer network fabrication toward the rational design of structural materials possessing dynamic characteristics for specialty applications. Herein, we discuss the unique attributes of CANs that must be considered when designing, fabricating, and characterizing these smart materials that respond to either thermal or photochemical stimuli. While there are many reversible reactions which to consider as possible cross-link candidates in CANs, there are very few that are readily and repeatedly reversible. Furthermore, characterization of the mechanical properties of CANs requires special consideration owing to their unique attributes. Ultimately, these attributes are what lead to the advantageous properties displayed by CANs, such as recyclability, healability, tunability, shape changes, an...

/pdf/covalent-adaptable-networks-cans-a-unique-paradigm-in-cross-1cy00t3up9.pdf

Covalent Adaptable Networks (CANs): A Unique Paradigm in Cross-Linked Polymers

In the past few years optical ring resonators have emerged as a new sensing technology for highly sensitive detection of analytes in liquid or gas. This article introduces the ring resonator sensing principle, describes various ring resonator sensor designs, reviews the current state of the field, and presents an outlook of possible applications and related research and development directions.

Optical ring resonators for biochemical and chemical sensing

A 2D, extremely stable, metal-organic framework (MOF), NENU-503, was successfully constructed. It displays highly selective and recyclable properties in detection of nitroaromatic explosives as a fluorescent sensor. This is the first MOF that can distinguish between nitroaromatic molecules with different numbers of NO2 groups.

A Fluorescent Sensor for Highly Selective Detection of Nitroaromatic Explosives Based on a 2D, Extremely Stable, Metal–Organic Framework

One of the most challenging tasks encountered in developing highly efficient electro-optic (EO) devices is to find a material system that possesses all desirable properties such as large EO coefficients, good thermal and mechanical stability, and low optical loss. In order to meet this stringent requirement, we have developed a series of crosslinkable EO dendrimers using the standardized AJL8-type chromophore as the center core and the furyl- and anthryl-containing dendrons as the periphery. Upon adding a trismaleimide (TMI) dienophile, these dendrimers could be in-situ crosslinked via the Diels-Alder cycloaddition and efficiently poled under a high electric field. Through this dynamic process, the spatially voided and π-electron-rich surrounding of the chromophore core changes into a dense and more aliphatic network, with the dipolar chromophore embedded and aligned inside. The resultant materials exhibit large EO coefficients (63-99 pm V -1 at 1.31 μm), excellent temporal stability (the original r 33 values remain unchanged at 100 °C for more than 500 h), and blue-shifted near-IR absorption. With these combined desirable properties, a poled EOD2/TMI film could be processed through multiple lithographic and etching steps to fabricate a racetrack-shaped micro-ring resonator. By coupling this ring resonator with a side-polished optical fiber, a novel broadband electric-field sensor with high sensitivity of 100 mV m -1 at 550 MHz was successfully demonstrated.

Highly efficient diels-alder crosslinkable electro-optic dendrimers for electric-field sensors

A novel electrooptic (EO) electric field (E-field) sensor based on side-polished fiber coupled with an EO polymer microring resonator is proposed and demonstrated. An EO polymer waveguide with a ring shape is fabricated on the polished flat of an optical fiber. Light in the fiber evanescently couples into the resonator and forms resonant modes for certain wavelengths and produces notches in the output intensity of the fiber. External electric fields change the index of refraction of the ring waveguide and therefore dither its resonant wavelengths. For light of wavelength on the slope of a resonance notch, a change in the output intensity can be detected. The sensor is all dielectric without metal layers to distort the measured E-field. The resonant structure allows the sensor to potentially have much higher sensitivity than other electrooptic sensors based on Mach-Zehnder or polarization modulation. Since electrooptic polymers have higher electrooptic coefficients, lower dielectric constants and faster electrooptic responses than inorganic crystals, higher sensitivity, lower invasiveness, and higher bandwidth of E-field sensing can be expected. This sensor eliminates unreliable fiber-to-waveguide butt coupling as well as the high propagation loss encountered in the long straight EO polymer waveguides of sensors based on Mach-Zehnder structures. By using the fiber itself as the supporting substrate of the ring waveguide, the sensor can have small size and low disturbance to the measured electric field. The concept is demonstrated using AJLS103 EO polymer. A sensitivity of 100 mV/m has been achieved at frequencies up to 550 MHz (limited by the measurement system)

All-Dielectric Electrooptic Sensor Based on a Polymer Microresonator Coupled Side-Polished Optical Fiber

The interaction of light propagating in the wave-guiding structures with the surrounding media through its evanescent field has been used to detect biochemical activities without labeling the target molecules. By introducing multiple slots in a dielectric waveguide, we found that a much stronger evanescent field could be achieved in the surrounding media while still maintaining good optical confinement. The experimental demonstration of microring resonator sensors using single-mode waveguides having three slots indicates a 5-fold increase in sensitivity for homogeneous sensing and more than 3-fold increase in sensitivity for surface sensing in comparison to those of a waveguide without slots. Numerical simulations suggest an even higher sensitivity enhancement (as high as 100 times) as more slots and larger waveguide widths are used.

Enhanced Evanescent Confinement in Multiple-Slot Waveguides and Its Application in Biochemical Sensing

Electro-optic polymer waveguides in electron beam sensitive polymethyl methacrylate (PMMA) polymer matrix doped with organic nonlinear chromophores could be directly patterned by electron beam exposure with high resolution and smoothness. The polymer in the exposed regions was removed with standard electron beam resist developer and without damaging the chromophore containing polymer waveguides. Feature sizes on the order of 100 nm could be clearly resolved. High quality microring resonators made of YL124/PMMA electro-optic polymer were successfully fabricated with this technique. The measured resonance extinction ratios were more than 16 dB and quality factors were in the range of 10(3) approximately 10(4).

Direct electron beam writing of electro-optic polymer microring resonators

The optical properties such as index of refraction and optical absorption of many chromophore-containing polymers are sensitive to the physical and chemical environment to which the polymers are exposed. To demonstrate such applications, chemical sensors to detect trace explosives are presented. The sensors use polymers that contain chromophores whose molecular structure consists of an electron donor and an electron acceptor connected by a charge-transfer bridge of conjugated π-orbital electrons. The polymers used for the trace explosives sensor are not poled, and the chromophores are randomly oriented in the polymer host. Waveguide microring resonator and fiber Bragg grating structures were used in these sensors to enhance the detection sensitivity. Because chromophores undergo photodecomposition under intense ultraviolet radiation, chromophore-containing polymers can be patterned with ultraviolet light to create optical resonator structures in a single photobleaching step. The chemical sensor has shown ...

http://depts.washington.edu/eooptic/members/Group%20members/SamyPapers/jp7118372.pdf

Haishan Sun

Papers

Highly efficient diels-alder crosslinkable electro-optic dendrimers for electric-field sensors

All-Dielectric Electrooptic Sensor Based on a Polymer Microresonator Coupled Side-Polished Optical Fiber

Enhanced Evanescent Confinement in Multiple-Slot Waveguides and Its Application in Biochemical Sensing

Direct electron beam writing of electro-optic polymer microring resonators

Chromophore-Containing Polymers for Trace Explosive Sensors