Ultraviolet (UV) absorption spectroscopy is a rapid and reagent-free method for the determination of nitrogen compounds in surface waters; however, its application in anthropogenically impacted systems is limited by matrix interferences. This study evaluates the use of UVC spectroscopy for quantifying nitrogen compounds in the Kłodnica River, a watercourse strongly influenced by industrial and mining activities. Absorbance was measured at 220 nm, 235 nm, 254 nm, and 275 nm for ultrapure water, potassium nitrate reference solutions, and five river samples, both before and after filtration through a 0.45 µm membrane. Filtration enabled separation of light scattering caused by suspended particles, while multi-wavelength analysis was applied to compensate for natural organic matter interference. The results show that reliable quantification is achieved using wavelength pairs based on 220 nm, where absorbance of nitrogen compounds dominates over background effects. In contrast, measurements at 235 nm were strongly affected by matrix components, resulting in unstable correction and poor agreement with reference concentrations. Absorbance differences confirmed the influence of turbidity. A clear relationship between wavelengths enabled effective correction. The findings highlight the importance of wavelength selection and site-specific correction strategies for UV-based monitoring in complex, anthropogenically impacted waters.

Entangled photon detection is essential for advancements in quantum communication, cryptography, and fundamental quantum mechanics experiments. This study introduces a novel application of unsupervised machine learning for identifying potential entangled photon events by analyzing voltage signals recorded from Silicon Multiplier Amplified Detectors (SiMPs). By framing photon detection as an anomaly detection problem, we employ the Isolation Forest (iForest) algorithm to isolate rare and distinctive signal patterns within large, noisy datasets without requiring labeled training data. This is the first application of iForest in the context of entangled photon detection. The method enables automated identification of anomalous events exhibiting time correlations across multiple measurement channels, offering a scalable and computationally efficient solution for real-time processing of experimental data in quantum optics.

Raman spectroscopy (RS) is an excellent photonic measurement technique that can be extremely useful for characterizing kidney stones. Using RS, we can obtain precise information about the chemical composition and microstructure of the crystals that comprise kidney stones. Therefore, this non-invasive technique makes identifying different types of stones possible. Additionally, Raman spectroscopy supported by electron microscopy (SEM) imaging enables us to relate a given kind of crystal to its morphology. This paper presents the results of ex situ analysis of real samples of an unknown type of human kidney stone using RS and SEM techniques, which led to attempts to identify the stone.

Impedance spectroscopy is an appropriate technique for studying the complexity of materials, in which their different frequency relationships can be exploited in such a manner that they can be efficiently separated. Barium strontium titanate BaSrTiO3 (BST) is a ferroelectric material with unique properties that make it useful in a range of electronic applications. BST plays an important role in the field of gas-sensing applications. The potential application of BST material as a gas sensor for detecting nitrogen dioxide (NO2) in the atmosphere was studied. Impedance spectroscopy studies were conducted across a wide frequency range from 10−1 to 106 Hz, in the temperature range of 100°C to 350°C and a relative humidity of 50%, and both in air and the presence of NO2 in concentrations from 0.5 to 5 ppm. The results of the impedance analysis indicate that the broadband models, which comprise both single and parallel RC elements, can accurately represent the NO2 gas interaction mechanism with the gas-sensitive layer of the BST material. These models were found to effectively capture changes in parameters associated with the interaction.

The paper presents, and compares the performance of, two optical sensing systems each based on a combination of two fibre Bragg gratings (FBGs) and where a simple measurement of transmitted or reflected power provides an alternative to specialist interrogators. In both configurations one of the FBGs acts as a reference whilst the other is used as the measuring element. It is shown that using FBGs with wide spectra results in higher dynamic range. The measurement of strain is used to demonstrate the behaviour of the proposed sensing systems. The performance of the two systems is compared experimentally and discussed with the insight of the simultaneous measurement of the spectra reaching the detector.

Impedance spectroscopy is an appropriate technique for studying the complexity of materials, in which their different frequency relationships can be exploited in such a manner, they can be efficiently separated. Barium strontium titanate BaSrTiO3 (BST) is a ferroelectric material with unique properties that make it useful in a range of electronic applications. BST plays an important role in the field of gas-sensing applications. The potential application of BST material as a gas sensor for detecting nitrogen dioxide (NO2) in the atmosphere was studied. Impedance spectroscopy studies were conducted across a wide frequency range from 10-1 to 106 Hz, in the temperature range of 100°C to 350°C and a relative humidity of 50%, and in both air and the presence of NO2 in concentrations from 0.5 to 5 ppm. The results of the impedance analysis indicate that the broadband models, which comprise both single and parallel RC elements, can accurately represent the NO2 gas interaction mechanism with the gas-sensitive layer of the BST material. These models were found to effectively capture changes in parameters associated with the interaction.

paper presents research on short wavelength infrared (SWIR) absorption spectroscopy for gas sensing. The study focuses on detecting methane and ammonia, significant gaseous analytes, using a broadband light source and optical spectrum analyzer. The research demonstrates the potential for detecting methane and ammonia gas. The study addresses the current needs of industrial gas metrology and emphasizes the importance of detecting methane and ammonia due to their environmental and industrial implications.

A microwave system dedicated to the detection of nitrogen dioxide in the harsh environment of the Norway highways is proposed. An optimized transmission line type of sensor coated with a tungsten trioxide thin film that changes its electrical properties under NO2 gas exposure is developed. The sensors' response (S) is given in degrees /GHz and it is calculated based on wideband measurements. The advantage of wideband measurements in comparison to a single value is based on multiple measurements taken at different frequencies, which greatly suppresses noise and enables measuring low target-gas concentrations within environments of high interfering compounds. Herein, the developed system works in 1.5 GHz - 4.5 GHz, and NO2 varies in the 0-20 ppm range. The optimal thickness of the gas-sensing layer is estimated to be around 410 nm taking the advantage of the magnetron sputtering technology with the glancing angle deposition technique. The advantage of the developed sensor is the possibility to work at ambient temperature without the need to heat up the sensors. The disadvantage of the developed sensors is longer response and recovery times; however, this issue will be a subject of research in the future.

The paper presents the design, operation, and proof of principle realisation and validation of a relatively cheap fibre optic strain sensor based on two fibre Bragg grating (FBG) elements with different spectral responses. Its performance is compared with the measurement capabilities of a FBG-based sensor that uses an optical interrogator.

Nitrogen dioxide (NO2) sensors utilising graft copolymers bearing poly(3-hexylthiophene) chains have been developed and investigated in terms of their operation parameters using different carrier gases (N2 or air) and in either dark conditions or with ultraviolet (UV) irradiation. Interestingly, sensor performance improved upon transition from N2 to air, with the inverse being true for most NO2 sensors. UV irradiation both improved sensor dynamics and stabilised the sensor electrical baseline, allowing sensors based on SilPEG to fulfil the requirements of sensing solutions used in industry (below 10% baseline drift after sensors reach saturation) and making them promising candidates for further development and applications. Based on conducted multi-variate experiments, an initial mechanism underlying the interplay of exposure to oxygen (present in air) and UV irradiation was postulated.

Controlling environmental pollution is a burning problem for all countries more than ever. Currently, due to the increasing industrialization, the number of days when the limits of air pollutants are over the threshold levels exceeds 80–85% of the year. Therefore, cheap and effective sensors are always welcome. One idea is to combine such solutions with cars and provide real-time information about the current pollution level. However, the environmental conditions are demanding, and thus the developed sensors need to be characterized by the high 3S parameters: sensitivity, stability and selectivity. In this paper, we present the results on the heterostructure of CuO/SnOx and SnOx/CuO as a possible approach for selective NO2 detection. The developed gas sensors exhibited lower operating temperature and high response in the wide range of NO2 and in a wide range of relative humidity changes. Material characterizations and impedance spectroscopy measurements were also conducted to analyze the chemical and electrical behavior.

In this study, I prepared BK7 glass slides coated by palladium (Pd) layer by PVD technique. These samples have been employed as plasmon active structures in classic Kretschmann-based SPR set-up. The application of H2 sensing structures based on palladium plasmonic active thin films have been tested and investigated. Hydrogen sensing properties of Pd films were investigated at room temperature The reflectances of p-polarized light from Pd thin films as a function of angle of incidence and wavelength were measured in synthetic air (or nitrogen) and in gas mixtures including hydrogen. Variations of the reflectance in the presence of hydrogen gas at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (0–2% vol/vol) without saturation behavior. The dynamic properties with various concentration of H2 at low temperature and dry gas mixtures was investigated and the effects of these factors on the hydrogen sensing properties were analyzed. Full Text: PDF ReferencesG. Korotcenkov, Handbook of Gas Sensor Materials: Properties, Advantages, and Shortcomings for Applications (Springer, New York 2013). CrossRef W. Jakubik, M. Urbanczyk, E. Maciak, "SAW hydrogen gas sensor based on WO3 and Pd nanostructures", Procedia Chemistry 1 (1), 200 (2009). CrossRef W. Jakubik, M. Urbanczyk, E. Maciak, T. Pustelny, "Bilayer Structures of NiOx and Pd in Surface Acoustic Wave and Electrical Gas Sensor Systems", Acta Physica Polonica A 116(3), 315 (2009). CrossRef E. Maciak, Z. Opilski, "Pd/V2O5 fiber optic hydrogen gas sensor", J. Phys. France IV 129, 137 (2005). CrossRef E. Maciak,. "Fiber optic sensor for H2 gas detection in the presence of methane based on Pd/WO3 low-coherence interferometric structure", Proc. SPIE 10455, UNSP 104550W (2017). CrossRef X. Bevenot, A. Truillet, C. Veillas, H. Gagnaire, M. Clement, "Hydrogen leak detection using an optical fibre sensor for aerospace applications", Sens. Actuators B 67, 57 (2000). CrossRef J. Homola, S.S. Yee, G. Gauglitz, "Surface plasmon resonance sensors: review", Sensors and Actuators B 54, 3 (1999). CrossRef H. Raether, Surface plasmons on smooth and rough surfaces and on gratings (Springer-Verlag, Berlin-Heidelberg 1988). CrossRef P. Tobiska, O. Hugon, A. Trouillet, H.Gagnarie, "An integrated optic hydrogen sensor based on SPR on palladium", Sensors and Actuators, B 74, 168 (2001). CrossRef Z. Opilski, E. Maciak, "Optical hydrogen sensor employing the phenomenon of the surface plasmons resonance in the palladium layer", Proc. SPIE 5576, 202 (2004). CrossRef T. Pustelny, E. Maciak, Z. Opilski, A. Piotrowska, E. Papis, K. Golaszewska, "Investigation of the ZnO sensing structure on NH3 action by means of the surface plasmon resonance method", European Physical Journal-Special Topics 154, 165 (2008). CrossRef E. Maciak, M. Procek, K. Kępska, A. Stolarczyk, "Study of optical and electrical properties of thin films of the conducting comb-like graft copolymer of polymethylsiloxane with poly(3-hexyltiophene) and poly(ethylene) glycol side chains for low temperature NO2 sensing", Thin Solid Films 618, 277 (2016). CrossRef

The main aim of this work was the design and development simple fiber optic Fabry-Perot interferometer (FPI) sensor devices for relative humidity (RH) sensing with emphasis on high sensitivity and good stability. The RH fiber FPI sensor is fabricated by coating the end of a cleaved standard multi-mode (MM) fiber with hydrophilic Nafion® sensing film. The Nafion® thin film acts as an active resonance cavity of the low-coherence interferometric sensing structure. The fringe pattern, which is caused by interfering light beam in the Nafion® thin film will shift as the RH changes because the water molecules will swell the Nafion® film and thus change optical pathlength of the sensing structure. The operating principle of a FPI sensor based on the adsorption and desorption of water vapour in the Nafion® and the limitations of this sensor type are discussed in this work. The fiber optic hygrometer was tested in the visible (400–900 nm) region of spectra for measurement of relative humidity (RH) in the range of 5.5–80% at room temperature (RT) in air. The fiber optic humidity sensor has a very short response time (t90 = 5–80 s) and a fast regeneration time (t10 = 5–12 s) as good as commercial sensors.

In this paper, a simple combination of spin-coating fabrication techniques and cost-efficient polymer material for the fabrication of optoelectronic NO2 sensor was investigated. A surface plasmon resonance (SPR) sensor was fabricated by chitosan thin films immobilized on the gold plasmonic active layer. Sensing structures were formed on the glass slides covered 50 nm thick Au films by spin-coating method from liquid chitosan salt phase. Polymeric thin film work as sensitive elements and transducer to get optical response from environment at room temperature (RT).

In this paper, the microwave-based gas sensors were tested as a potentially sensors in portable breath analyzers for monitoring biomarkers in exhaled breath, such as: acetone and ethanol. The obtained sensor's response was approximately 14 MHz/ppm for acetone and 3 MHz/ppm for ethanol. The comb copolymer phthalocyanine thin films were deposited as a sensitive layer. Fabricated sensors have been also verified under exposure to other volatile organic compounds, such as: methanol, butanol. The obtained results showed that microwave-based gas senors can be applied for acetone measurements.

In this paper, a simple combination of dip-coating fabrication techniques and cost-efficient copolymer grafted phthalocyanine material for the fabrication of fiber optic NO2 sensor was investigated. A fiber optic sensor was fabricated by organic thin films immobilized on the end-face of an optical fiber. Sensing nanostructure were formed on the end-face of an optical fiber by dip-coating method from liquid phase. Polymeric thin film work as sensitive elements and transducer to get optical response and feedback from environments, in which optical fibers are employed to work as signal carrier.

In this paper graft copolymer of poly(3-hexylthiophene) and poly(ethylene) glycol on the polymethylsiloxane core are investigated as a receptor material for resistance gas sensor. Sensor response to 5 ppm of NO2 and its recovery after the interaction with NO2 are studied at different conditions: room temperature (RT), RT with ultraviolet (UV) radiation and at elevated temperature (50 °C). Results shows that sensor regeneration occurred faster at RT with UV than at 50 °C in dark conditions. The sensor response at RT is also higher than at 50 °C. The mixed operation conditions, namely dark conditions for adsorption and UV for desorption, provides high sensor response (3590% for 5 ppm of NO2) and relatively good regeneration (250% deviation from base-line after 30 min). Thanks to this investigated graft copolymers are promising receptor materials for chemical NO2 sensors operating at RT.

An interdigital capacitor with resonant frequency fres N 8.6 GHz coated by comb polymer Pc-based thin film as a sensitive layer was investigated under exposure to different concentrations of various VOCs, such as: acetone, ethanol, methanol, isopropanol, butanol and ethylbenzene in a 0-25 ppm concentration range. The measurement system has been significantly simplified due to measurement of the reflection coefficient at a single frequency f(o) = 8 GHz, at which the sensor exhibits the largest change in reflection coefficient's magnitude. For the reflection coefficient's measurement a new six-port reflectometer has been developed, which provides an enhanced measurement accuracy for the measurements of reflection coefficients having small magnitudes. The developed detector based on microwave measurements can be utilized in a portable exhaled breath analyzers. (C) 2017 Elsevier B.V. All rights reserved.

In this work, novel conducting graft copolymers: [...]

This work presents an investigation on conductive graft comb copolymer like SILPEG CH9 with carbon materials like graphite oxide or reduced graphite oxide. Morphology and optical properties like sample roughness, graphite oxide particles distribution, optical transmittance were measured of obtained thin films deposited on glass substrate using spin coating method. The study showed that obtained thin films are repeatable, convenient to process, and their parameters can be easy changed by the spin rate regulation during the deposition. Given results shows the possibility of using such polymer blend in the implementation of organic photovoltaic cells and different optoelectronics applications.