Optical fiber sensors based on microstructured optical fibers to detect gases and volatile organic compounds-A review

Since the first publications related to microstructured optical fibers (MOFs), the development of optical fiber sensors (OFS) based on them has attracted the interest of many research groups because of the market niches that can take advantage of their specific features. Due to their unique structure based on a certain distribution of air holes, MOFs are especially useful for sensing applications: on one hand, the increased coupling of guided modes into the cladding or the holes enhances significantly the interaction with sensing films deposited there; on the other hand, MOF air holes enhance the direct interaction between the light and the analytes that get into in these cavities. Consequently, the sensitivity when detecting liquids, gasses or volatile organic compounds (VOCs) is significantly improved. This paper is focused on the reported sensors that have been developed with MOFs which are applied to detection of gases and VOCs, highlighting the advantages that this type of fiber offers.This work was carried out with the financial support of MINECO (Spain) through TEC2016-79367-C2-2-R (AEI/FEDER, UE) as well as Public University of Navarre PhD grants program.This work was carried out with the financial support of MINECO (Spain) through TEC2016-79367-C2-2-R (AEI/FEDER, UE)

Straightforward nano patterning on optical fiber for sensors development

A simple method to prepare a nano pattern along the surface of an optical fiber is applied in this Letter to develop a pH sensor. The template is made of a block copolymer that defines specific locations where gold nano particles are adsorbed on forming clusters. The average diameter of the resulting agglomerates is 121 nm, and the mean distance between the centers is 182 nm. The morphology of the gold cluster array produces localized surface plasmon resonance. The absorbance spectrum is affected by pH variations, and the ratio between the absorption at two different wavelengths is used to characterize the response, which is repetitive and reversible. This Letter highlights the potentiality of this type of chemical nano patterning for the development of optical fiber sensors.Agencia Estatal de Investigación; Ministerio de Economía y Competitividad (TEC2016-79367-C2-2-R); Government of Navarra (PI035 BINACS)

Comparative study of layer-by-layer deposition techniques for poly(sodium phosphate) and poly (allylamine hydrochloride)

UPNa. Departamento de Ingeniería Eléctrica y Electrónica. Laboratorio de Dispositivos Ópticos NanoestructuradosAn inorganic short chain polymer, poly(sodium phosphate), PSP, together with poly(allylamine hydrochloride), PAH, is used to fabricate layer-by-layer (LbL) films. The thickness, roughness, contact angle, and optical transmittance of these films are studied depending on three parameters: the precursor solution concentrations (10−3 and 10−4 M), the number of bilayers deposited (20, 40, 60, 80, and 100 bilayers), and the specific technique used for the LbL fabrication (dipping or spraying). In most cases of this experimental study, the roughness of the nanofilms increases with the number of bilayers. This contradicts the basic observations made in standard LbL assemblies where the roughness decreases for thicker coatings. In fact, a wide range of thickness and roughness was achieved by means of adjusting the three parameters mentioned above. For instance, a roughness of 1.23 or 205 nm root mean square was measured for 100 bilayer coatings. Contact angles close to 0 were observed. Moreover, high optical transmittance is also reported, above 90%, for 80 bilayer films fabricated with the 10−4 M solutions. Therefore, these multilayer structures can be used to obtain transparent superhydrophilic surfaces.This work was supported by the Spanish Economy and Competitiveness Ministry-FEDER TEC2010-17805

Volatile organic compound optical fiber sensors: a review

Volatile organic compound (VOC) detection is a topic of growing interest with applications in diverse fields, ranging from environmental uses to the food or chemical industries. Optical fiber VOC sensors offering new and interesting properties which overcame some of the inconveniences found on traditional gas sensors appeared over two decades ago. Thanks to its minimum invasive nature and the advantages that optical fiber offers such as light weight, passive nature, low attenuation and the possibility of multiplexing, among others, these sensors are a real alternative to electronic ones in electrically noisy environments where electronic sensors cannot operate correctly. In the present work, a classification of these devices has been made according to the sensing mechanism and taking also into account the sensing materials or the different methods of fabrication. In addition, some solutions already implemented for the detection of VOCs using optical fiber sensors will be described with detail.This work was supported by Spanish Ministerio de Ciencia y Tecnología and FEDER Research Grants CICYT-TIC 2003-000909 and CICYT-TEC 2004-05936-C02-01/MIC