http://www.mdpi.com/journal/sensors/special_issues/detection_sensors/ Dear Colleagues, Photonic sensors, including fiber optic sensors, have been the subject of intensive research over the last two decades for use in civil and military environments for detection of a wide variety of biological, chemical and nuclear agents. Photonic sensor designs have been developed and demonstrated that have small size, light weight, high resolution, immunity to electromagnetic interference, harsh environment operational capability, “long-reach” access potential, multiplexing capability for certain sensor designs and low cost implementation attributes. Photonic sensors can utilize different components of the optical signal such as intensity based, interferometric, polarization, spectroscopic, pulse shape or arrival time based, giving rise to a large number of different sensor designs. These differences may arise in the physical structures employed, in the optical source or detection systems, in the signal demodulation systems, or in new combinations of these. Progress in photonic sensor designs and applications continues at a fast pace with new types of optical fibers - photonic band gap fibers (PBG), microstructure optical fibers (MOF), random hole optical fibers (RHOF); and hybrid ordered random hole optical fibers (HORHOF); higher resolution, lower cost, and or expanded detection range capability for sources and detection schemes; and new signal demodulation algorithm designs. Within this rapidly advancing field, this special issue focuses on photonic sensors for chemical, biological and nuclear agent detection. I hope that this special issue will give the reader a broad overview of some of the exciting areas of photonic sensor research with this collection of innovative research articles. Dr. Teng K. OoiDr. Gary R. PickrellGuest Editors{snippet name="submission_info"} http://www.mdpi.com/1424-8220/8/4/2453/ The ever increasing demand for in situ monitoring of health, environment and security has created a need for reliable, miniaturised sensing devices. To achieve this, appropriate analytical devices are required that possess operating characteristics of reliability, low power consumption, low cost, autonomous operation capability and compatibility with wireless communications systems. The use of light emitting diodes (LEDs) as light sources is one strategy, which has been successfully applied in chemical sensing. This paper summarises the development and advancement of LED based chemical sensors and sensing devices in terms of their configuration and application, with the focus on transmittance and reflectance absorptiometric measurements. http://www.mdpi.com/1424-8220/8/4/2453/ Mon, 07 Apr 2008 00:00:00 CEST Sensors 2008-04-07 8 4 Review 2453 2479 1424-8220 Absorbance Based Light Emitting Diode Optical Sensors and Sensing Devices 2008-04-07 doi: 10.3390/s8042453 Martina O’Toole Dermot Diamond http://www.mdpi.com/1424-8220/8/3/1960/ Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film using the ion sputtering technique. Light is then sent into a fiber embedded in concrete and the reflected signal is monitored. Initially, most of the light is reflected by the iron layer. When corrosion occurs to remove the iron layer, a significant portion of the light power will leave the fiber at its exposed end, and the reflected power is greatly reduced. Monitoring of the reflected signal is hence an effective way to assess if the concrete environment at the location of the fiber tip may induce steel corrosion or not. In this paper, first the principle of the corrosion sensor and its fabrication are described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation will be presented and the performance of the packaged sensors is assessed by additional experiments. http://www.mdpi.com/1424-8220/8/3/1960/ Thu, 20 Mar 2008 00:00:00 CET Sensors 2008-03-20 8 3 Article 1960 1976 1424-8220 A Novel Optical Fiber Sensor for Steel Corrosion in Concrete Structures 2008-03-20 doi: 10.3390/s8031960 Christopher K.Y. Leung Kai Tai Wan Liquan Chen http://www.mdpi.com/1424-8220/8/2/847/ An optical fibre sensor has been implemented towards pyridine vapors detection;to achieve this, a novel vapochromic material has been used, which, in solid state, suffers achange in colour from blue to pink-white in presence of pyridine vapours. This complex isadded to a solution of PVC (Poly Vinyl Chloride), TBP (Tributylphosphate) andtetrahydrofuran (THF), forming a plasticized matrix; by dip coating technique, the sensingmaterial is fixed onto a cleaved ended optical fibre. The fabrication process was optimizedin terms of number of dips and dipping speed, evaluating the final devices by dynamicrange. Employing a reflection set up, the absorbance spectra and changes in the reflectedoptical power of the sensors were registered to determine their response. A linear relationbetween optical power versus vapor concentration was obtained, with a detection limit of 1ppm (v/v). http://www.mdpi.com/1424-8220/8/2/847/ Fri, 08 Feb 2008 00:00:00 CET Sensors 2008-02-08 8 2 Article 847 859 1424-8220 Pyridine Vapors Detection by an Optical Fibre Sensor 2008-02-08 doi: 10.3390/s8020847 Cesar Elosua Candido Bariain Ignacio R. Matias Antonio Rodriguez Enriquie Colacio Alfonso Salinas-Castillo Antonio Segura-Carretero Alberto Fernandez-Gutiérrez http://www.mdpi.com/1424-8220/8/1/171/ A simple and effective method is proposed to improve spectral sensitivity anddetection limit of long period gratings for refractive index or chemical sensing, where thegrating surface is modified by a monolayer of colloidal gold nanoparticles. Thetransmission spectra and optical properties of gold nanospheres vary with the differentrefractive index of the environment near the surface of gold nanospheres. The sensorresponse of gold colloids increases linearly with solvents of increasing refractive index.The results for the measurement of sucrose and sodium chloride solutions are reported,which show that this type of sensor can provide a limiting resolution of ~10-3 to ~10-4 forrefractive indices in the range of 1.34 to 1.39 and a noticeable increase in detection limit ofrefractive index to external medium. http://www.mdpi.com/1424-8220/8/1/171/ Mon, 21 Jan 2008 00:00:00 CET Sensors 2008-01-21 8 1 Article 171 184 1424-8220 Chemical Sensing Sensitivity of Long-Period Grating Sensor Enhanced by Colloidal Gold Nanoparticles 2008-01-21 doi: 10.3390/s8010171 Jaw-Luen Tang Jien-Neng Wang http://www.mdpi.com/1424-8220/7/12/3100/ Protection of public and military personnel from chemical and biological warfareagents is an urgent and growing national security need. Along with this idea, we havedeveloped a novel class of fiber optic chemical sensors, for detection of toxic and biologicalmaterials. The design of these fiber optic sensors is based on a cladding modificationapproach. The original passive cladding of the fiber, in a small section, was removed and thefiber core was coated with a chemical sensitive material. Any change in the opticalproperties of the modified cladding material, due to the presence of a specific chemicalvapor, changes the transmission properties of the fiber and result in modal powerredistribution in multimode fibers. Both total intensity and modal power distribution (MPD)measurements were used to detect the output power change through the sensing fibers. TheMPD technique measures the power changes in the far field pattern, i.e. spatial intensitymodulation in two dimensions. Conducting polymers, such as polyaniline and polypyrrole,have been reported to undergo a reversible change in conductivity upon exposure tochemical vapors. It is found that the conductivity change is accompanied by optical propertychange in the material. Therefore, polyaniline and polypyrrole were selected as the modifiedcladding material for the detection of hydrochloride (HCl), ammonia (NH3), hydrazine(H4N2), and dimethyl-methl-phosphonate (DMMP) {a nerve agent, sarin stimulant},respectively. Several sensors were prepared and successfully tested. The results showeddramatic improvement in the sensor sensitivity, when the MPD method was applied. In thispaper, an overview on the developed class of fiber optic sensors is presented and supportedwith successful achieved results. http://www.mdpi.com/1424-8220/7/12/3100/ Tue, 04 Dec 2007 00:00:00 CET Sensors 2007-12-04 7 12 Article 3100 3118 1424-8220 Fiber Optic Sensors For Detection of Toxic and Biological Threats 2007-12-04 doi: 10.3390/s7123100 Mahmoud El-Sherif Lalitkumar Bansal Jianming Yuan http://www.mdpi.com/1424-8220/7/11/2808/ Many organisms secrete antimicrobial peptides (AMPs) for protection againstharmful microbes. The present study describes detection of botulinum neurotoxoids A, Band E using AMPs as recognition elements in an array biosensor. While AMP affinitieswere similar to those for anti-botulinum antibodies, differences in binding patterns wereobserved and can potentially be used for identification of toxoid serotype. Furthermore,some AMPs also demonstrated superior detection sensitivity compared to antibodies: toxoidA could be detected at 3.5 LD50 of the active toxin in a 75-min assay, whereas toxoids B andE were detected at 14 and 80 LD50 for their respective toxins. http://www.mdpi.com/1424-8220/7/11/2808/ Fri, 16 Nov 2007 00:00:00 CET Sensors 2007-11-16 7 11 Article 2808 2824 1424-8220 Antimicrobial Peptides: New Recognition Molecules for Detecting Botulinum Toxins 2007-11-16 doi: 10.3390/s7112808 Nadezhda V. Kulagina George P. Anderson Frances S. Ligler Kara M. Shaffer Chris Rowe Taitt http://www.mdpi.com/1424-8220/7/11/2741/ A very compact (device area around 40 μm2) optical ammonia sensor based on amicroring resonator is presented in this work. Silicon-on-insulator technology is used insensor design and a dye doped polymer is adopted as sensing material. The sensor exhibitsa very good linearity and a minimum detectable refractive index shift of sensing materialas low as 8x10-5, with a detection limit around 4 ‰. http://www.mdpi.com/1424-8220/7/11/2741/ Thu, 15 Nov 2007 00:00:00 CET Sensors 2007-11-15 7 11 Article 2741 2749 1424-8220 Ammonia Optical Sensing by Microring Resonators 2007-11-15 doi: 10.3390/s7112741 Vittorio M. N. Passaro Francesco Dell’Olio Francesco De Leonardis http://www.mdpi.com/1424-8220/7/11/2492/ A new class of refractive index sensors using solid core photonic crystal fibres isdemonstrated. Coherent scattering at the cladding lattice is used to optically characterizematerials inserted into the fibre holes. The liquid to solid phase transition of water uponfreezing to ice 1h is characterized by determining the refractive index. http://www.mdpi.com/1424-8220/7/11/2492/ Tue, 30 Oct 2007 00:00:00 CET Sensors 2007-10-30 7 11 Article 2492 2498 1424-8220 Refractive Index Measurement within a Photonic Crystal Fibre Based on Short Wavelength Diffraction 2007-10-30 doi: 10.3390/s7112492 Cicero Martelli John Canning Martin Kristensen Nathaniel Groothoff http://www.mdpi.com/1424-8220/7/5/676/ Effects of radiation on sensing and data transmission components are of greatinterest in many applications including homeland security, nuclear power generation, andmilitary. A new type of microstructured optical fiber (MOF) called the random hole opticalfiber (RHOF) has been recently developed. The RHOFs can be made in many differentforms by varying the core size and the size and extent of porosity in the cladding region.The fibers used in this study possessed an outer diameter of 110 μm and a core ofapproximately 20 μm. The fiber structure contains thousands of air holes surrounding thecore with sizes ranging from less than 100 nm to a few μm. We present the first study ofthe behavior of RHOF under gamma irradiation. We also propose, for the first time to ourknowledge, an ionizing radiation sensor system based on scintillation light from ascintillator phosphor embedded within a holey optical fiber structure. The RHOF radiationresponse was compared to normal single mode and multimode commercial fibers(germanium doped core, pure silica cladding) and to those of radiation resistant fibers (puresilica core with fluorine doped cladding fibers). The comparison was done by measuringradiation-induced absorption (RIA) in all fiber samples at the 1550 nm wavelength window(1545 ± 25 nm). The study was carried out under a high-intensity gamma ray field from a 60Co source (with an exposure rate of 4x104 rad/hr) at an Oak Ridge National Laboratory gamma ray irradiation facility. Linear behavior, at dose values less than 106 rad, was observed in all fiber samples except in the pure silica core fluorine doped cladding fiber which showed RIA saturation at 0.01 dB. RHOF samples demonstrated low RIA (0.02 and 0.005 dB) compared to standard germanium doped core pure silica cladding (SMF and MMF) fibers. Results also showed the possibility of post-fabrication treatment to improve the radiation resistance of the RHOF fibers. http://www.mdpi.com/1424-8220/7/5/676/ Thu, 24 May 2007 00:00:00 CEST Sensors 2007-05-24 7 5 Article 676 688 1424-8220 Behavior of Random Hole Optical Fibers under Gamma Ray Irradiation and Its Potential Use in Radiation Sensing Applications 2007-05-24 doi: 10.3390/s7050676 Bassam Alfeeli Gary Pickrell Marc A. Garland Anbo Wang http://www.mdpi.com/1424-8220/6/8/848/ A low-power, high sensitivity, very low-cost light emitting diode (LED)-baseddevice developed for low-cost sensor networks was modified with bromocresol greenmembrane to work as a solid-state pH sensor. In this approach, a reverse-biased LEDfunctioning as a photodiode is coupled with a second LED configured in conventionalemission mode. A simple timer circuit measures how long (in microsecond) it takes for thephotocurrent generated on the detector LED to discharge its capacitance from logic 1 ( 5 V)to logic 0 ( 1.7 V). The entire instrument provides an inherently digital output of lightintensity measurements for a few cents. A light dependent resistor (LDR) modified withsimilar sensor membrane was also used as a comparison method. Both the LED sensor andthe LDR sensor responded to various pH buffer solutions in a similar way to obtainsigmoidal curves expected of the dye. The pKa value obtained for the sensors was found toagree with the literature value. http://www.mdpi.com/1424-8220/6/8/848/ Wed, 23 Aug 2006 00:00:00 CEST Sensors 2006-08-23 6 8 Article 848 859 1424-8220 Solid State pH Sensor Based on Light Emitting Diodes (LED) As Detector Platform 2006-08-23 doi: 10.3390/s6080648 King Tong Lau R. Shepherd Danny Diamond Dermot Diamond http://www.mdpi.com/1424-8220/6/8/835/ A fiber optic intrinsic Fabry-Perot interferometric (IFPI) chemical sensor wasdeveloped by fine-polishing a thin layer of polycrystalline nanoporous MFI zeolitesynthesized on the cleaved endface of a single mode fiber. The sensor operated bymonitoring the optical thickness changes of the zeolite thin film caused by the adsorption oforganic molecules into the zeolite channels. The optical thickness of the zeolite thin filmwas measured by white light interferometry. Using methanol, 2-propanol, and toluene as themodel chemicals, it was demonstrated that the zeolite IPFI sensor could detect dissolvedorganics in water with high sensitivity. http://www.mdpi.com/1424-8220/6/8/835/ Tue, 22 Aug 2006 00:00:00 CEST Sensors 2006-08-22 6 8 Article 835 847 1424-8220 Nanoporous Zeolite Thin Film-Based Fiber Intrinsic Fabry-Perot Interferometric Sensor for Detection of Dissolved Organics in Water 2006-08-22 doi: 10.3390/s6080835 Ning Liu Juan Hui Cunqiang Sun Junhang Dong Luzheng Zhang Hai Xiao http://www.mdpi.com/1424-8220/6/8/823/ Optical sensors have been investigated and widely deployed in industrial andscientific measurement and control processes, mainly due to their accuracy, high sensitivityand immunity to electromagnetic interference and other unique characteristics. They areespecially suited for harsh environments applications, where no commercial electricalsensors are available for long-term stable operations. This paper reports a novel contactoptical high temperature sensor targeting at harsh environments. Utilizing birefringentsingle crystal sapphire as the sensing element and white light interferometric signalprocessing techniques, an optical birefringence based temperature sensor was developed.With a simple mechanically structured sensing probe, and an optical spectrum-codedinterferometric signal processor, it has been tested to measure temperature up to 1600 °Cwith high accuracy, high resolution, and long-term measurement stability. http://www.mdpi.com/1424-8220/6/8/823/ Mon, 21 Aug 2006 00:00:00 CEST Sensors 2006-08-21 6 8 Article 823 834 1424-8220 Single-crystal Sapphire Based Optical Polarimetric Sensor for High Temperature Measurement 2006-08-21 doi: 10.3390/s6080823 Yibing Zhang Gary R. Pickrell Bing Qi Ahmad Safaai-Jazi Anbo Wang http://www.mdpi.com/1424-8220/6/8/808/ Recent outbreaks of food borne illnesses continue to support the need for rapidand sensitive methods for detection of foodborne pathogens. A method for detecting Listeriamonocytogenes in food samples was developed using an automated fiber-optic-basedimmunosensor, RAPTORTM. Detection of L. monocytogenes in phosphate buffered saline(PBS) was performed to evaluate both static and flow through antibody immobilizationmethods for capture antibodies in a sandwich assay. Subsequent detection in frankfurtersamples was conducted using a flow through immobilization system. A two stage blockingusing biotinylated bovine serum albumin (b-BSA) and BSA was effectively employed toreduce the non-specific binding. The sandwich assay using static or flow through mode ofantibody immobilization could detect 1 http://www.mdpi.com/1424-8220/6/8/808/ Sat, 19 Aug 2006 00:00:00 CEST Sensors 2006-08-19 6 8 Article 808 822 1424-8220 Antibody Immobilization on Waveguides Using aFlow–Through System Shows Improved Listeria monocytogenesDetection in an Automated Fiber Optic Biosensor: RAPTORTM 2006-08-19 doi: 10.3390/s6080808 Viswaprakash Nanduri Giyoung Kim Mark T. Morgan Daniel Ess Byoung-Kwon Hahm Aparna Kothapalli Angela Valadez Tao Geng Arun K. Bhunia http://www.mdpi.com/1424-8220/6/8/796/ Fiber optic biosensor has a great potential to meet the need for rapid, sensitive,and real-time microbial detection systems. We developed an antibody-based fiber-opticbiosensor to rapidly detect low levels of Escherichia coli O157:H7 cells in ground beef. Theprinciple of the sensor is a sandwich immunoassay using an antibody which is specific forE. coli O157:H7. A polyclonal antibody was first immobilized on polystyrene fiberwaveguides through a biotin-streptavidin reaction that served as a capture antibody. AnAlexa Fluor 647 dye-labeled antibody to E. coli O157:H7 was used to detect cells andgenerate a specific fluorescent signal, which was acquired by launching a 635 nm laser-lightfrom an Analyte-2000. Fluorescent molecules within several hundred nanometers of thefiber were excited by an evanescent wave, and a portion of the emission light fromfluorescent dye transmitted by the fiber and collected by a photodetector at wavelengths of670 to 710 nm quantitatively. This immunosensor was specific for E. coli O157:H7compared with multiple other foodborne bacteria. In addition, the biosensor was able todetect as low as 103 CFU/ml pure cultured E. coli O157:H7 cells grown in culture broth.Artificially inoculated E. coli O157:H7 at concentration of 1 CFU/ml in ground beef couldbe detected by this method after only 4 hours of enrichment. http://www.mdpi.com/1424-8220/6/8/796/ Sat, 19 Aug 2006 00:00:00 CEST Sensors 2006-08-19 6 8 Article 796 807 1424-8220 Fiber-Optic Biosensor Employing Alexa-Fluor Conjugated Antibody for Detection of Escherichia coli O157:H7 from Ground Beef in Four Hours 2006-08-19 doi: 10.3390/s6080796 Tao Geng Joe Uknalis Su-I Tu Arun K. Bhunia http://www.mdpi.com/1424-8220/6/8/785/ We have developed an optical microsphere resonator biosensor using aptamer asreceptor for the measurement of the important biomolecule thrombin. The sphere surface ismodified with anti-thrombin aptamer, which has excellent binding affinity and selectivityfor thrombin. Binding of the thrombin at the sphere surface is monitored by the spectralposition of the microsphere’s whispering gallery mode resonances. A detection limit on theorder of 1 NIH Unit/mL is demonstrated. Control experiments with non-aptameroligonucleotide and BSA are also carried out to confirm the specific binding betweenaptamer and thrombin. We expect that this demonstration will lead to the development ofhighly sensitive biomarker sensors based on aptamer with lower cost and higher throughputthan current technology. http://www.mdpi.com/1424-8220/6/8/785/ Wed, 16 Aug 2006 00:00:00 CEST Sensors 2006-08-16 6 8 Article 785 795 1424-8220 Aptamer Based Microsphere Biosensor for Thrombin Detection 2006-08-16 doi: 10.3390/s6080785 Hongying Zhu Jonathan D. Suter Ian M. White Xudong Fan http://www.mdpi.com/1424-8220/6/8/783/ n/a http://www.mdpi.com/1424-8220/6/8/783/ Tue, 15 Aug 2006 00:00:00 CEST Sensors 2006-08-15 6 8 Other 783 784 1424-8220 Special Issue of Photonic Sensors for Chemical, Biological, and Physical Parameter Detection 2006-08-15 doi: 10.3390/s6080783 Gary Pickrell