The enthralling properties of lanthanide luminescence have propelled luminescent probes, tags and materials based on these elements to the forefront of science and technology. In this minireview, attention is focused on the latest innovations and on less-known aspects of this field. Exciting new developments in bioimaging, therapy, drug delivery, security tags, luminescent sensors, and solar energy conversion are highlighted.

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Intriguing aspects of lanthanide luminescence

This paper gives a review of acoustic and ultrasonic optical fiber sensors (OFSs). The review covers optical fiber sensing methods for detecting dynamic strain signals, including general sound and acoustic signals, high-frequency signals, i.e., ultrasonic/ultrasound, and other signals such as acoustic emissions, and impact induced dynamic strain. Several optical fiber sensing methods are included, in an attempted to summarize the majority of optical fiber sensing methods used to date. The OFS include single fiber sensors and optical fiber devices, fiber-optic interferometers, and fiber Bragg gratings (FBGs). The single fiber and fiber device sensors include optical fiber couplers, microbend sensors, refraction-based sensors, and other extrinsic intensity sensors. The optical fiber interferometers include Michelson, Mach-Zehnder, Fabry-Perot, Sagnac interferometers, as well as polarization and model interference. The specific applications addressed in this review include optical fiber hydrophones, biomedical sensors, and sensors for nondestructive evaluation and structural health monitoring. Future directions are outlined and proposed for acousto-ultrasonic OFS.

/pdf/acousto-ultrasonic-optical-fiber-sensors-overview-and-state-4ugoielu3j.pdf

Acousto-Ultrasonic Optical Fiber Sensors: Overview and State-of-the-Art

Chapter 225 – Rare-earth beta-diketonates

A state-of-the-art review is presented regarding the research and development of in situ fibre optic damage detection and assessment systems (FODDAS) embedded in fibre-reinforced composite structures. Representative individual fibre optic strain sensors and distributed sensor networks are briefly described. A major emphasis is placed on their capabilities for detecting damage, determining damage location and assessing the nature of damage, arising primarily from specific events such as impacts or quasi-static stress overloads. The main features of such systems as custom-built and structure-specific units with minimal human involvement are highlighted. Issues that could affect the validity of the performance of such strain sensors are discussed. Fracture and non-fracture of fibre optic sensors are identified as two fundamentally different approaches for damage detection and their primary features are discussed in relation to location determination and evaluation of the nature of damage. The major advantages and limitations of each approach are discussed. Directions and areas of potential future research in the development of related FODDAS are highlighted.

http://iopscience.iop.org/article/10.1088/0964-1726/11/6/314/pdf

Damage detection and assessment in fibre-reinforced composite structures with embedded fibre optic sensors-review

Triboluminescence: Recalling Interest and New Aspects

A damage sensor for detecting damage within a structure such as aircraft wings or fuselage, or a bridge. The sensor comprises a small piece of a triboluminescent material connected via light guiding fibres or layers to one or more detectors. The sensor may be embedded within the structure or mounted on its surface. Impact of objects on the structure causes a physical damage to the triboluminescent material. Such damage causes light emission which is detected and recorded for later observation. The intensity of emission may be measured to give an indication of amount of damage received by the structure. Several different triboluminescent materials may be arranged in different location within the structure so that location of damage may be detected by a single detector sensitive to the different wavelengths of light emitted by the several materials. Light from the triboluminescent material may be detected directly by the detectors. Alternatively, material doped with suitable photo excitable dyes may be caused to photo excite, and the resultant light output detected.

https://iopscience.iop.org/article/10.1088/0964-1726/8/4/308/pdf

Triboluminescent damage sensors

Currently, there are no simple sensing techniques for determining in real-time both the severity and location of structural damage in a composite caused by a dynamic impact event. Materials are known which emit light when they are fractured. This fracture-induced light emissions is known as triboluminescence. A triboluminescent material embedded in, or attached on, a composite structure could act as a real- time damage sensor. The occurrence and severity of the damage is given by the intensity of the resulting triboluminescent light. Since the triboluminescent light emission is fracture-initiated, no signal would be generated by a triboluminescent sensor until damage had actually occurred. Hence no false alarms are generated by this type of sensor. An array of triboluminescent sensors may allow real-time damage location monitoring simply by determining the wavelength of the emitted light. We have developed a series of highly efficient triboluminescent materials with sufficient thermal and chemical properties to allow doping into composites. We report a series of proof-of-principle experiments with these materials which strongly support the potential of triboluminescent sensors to monitor in real- time both the magnitude and location of structural damage.

Squeezing light out of crystals: triboluminescent sensors

A molecular single electron transistor (MSET) detector device ( 14 ) is described that comprises at least one organic molecule ( 87 ) connecting a drain electrode ( 84 ) and a source electrode ( 82 ). In use, said at least one organic molecule ( 87 ) provides a quantum confinement region. At least one analyte receptor site ( 90, 92 ) is provided in the vicinity of said at least one organic molecule ( 87 ) that bind molecules of interest (analytes). A fluid analyser ( 2 ) is also described that includes the MSET detector, a pre-concentrator ( 4 ) and a fluid gating structure ( 6 ). The fluid gating structure ( 6 ) is arranged to selectively route fluid from the pre-concentrator ( 4 ) to either one of the detector ( 14 ) and an exhaust port ( 12 ). The pre-concentrator ( 4 ), fluid gating structure ( 6 ) and detector ( 14 ) are each formed as substantially planar layers and arranged in a stack or cube.

Norman James Geddes

Papers

Triboluminescent damage sensors

Squeezing light out of crystals: triboluminescent sensors

Molecular single electron transistor (mset) detector device