Optical Nose Research Articles

Miniaturized Sniffing Device based on an Array of Fluorescent Carbon Quantum Dots and Metallic Nanoclusters Efficiently Identifies Hematologic Malignancy in Adults.

The study demonstrates the potential of an optical nose made by depositing an array of fluorescent nanomaterials on a paper substrate for the early detection of leukemia in adults. This is based on the fact that blood volatile organic compounds (VOCs) are useful leukemia biomarkers. The integrated design was miniaturized and comprised both sensing zones and a sample holding zone, which were installed on a small sheet of paper within a miniature cubic reaction chamber fabricated by using 3D printing technology. The sensing device, comprising seven fluorescent sensing elements, namely, metal nanoclusters, quantum dots, and carbon dots was capable of detecting VOCs in the blood headspace and providing a colorimetric signature that could discriminate between blood samples from healthy and cancerous individuals. A total of 70 new leukemia cases and 51 healthy controls aged 20-50 years were studied. The device required a 60 μL portion of the blood sample and reacted to blood VOCs after 3 h when kept at 50 °C. The imaging data from the device was processed by linear discriminant analysis, and the results confirmed efficient identification of patient samples from healthy samples with 100% accuracy. Overall, the array system is noninvasive (or minimally invasive), portable, fast, inexpensive, and requires only a small amount of blood sample.

Scalable Optical Nose Realized with a Chemiresistively Modulated Light-Emitter Array.

Biological olfaction relies on a large number of receptors that function as sensors to detect gaseous molecules. It is challenging to realize artificial olfactory systems that contain similarly large numbers of sensory materials. It is shown that combinatorial materials processing with vapor deposition can be used to fabricate large arrays of distinct chemiresistive sensing materials. By combining these with light-emitting diodes, an array of chemiresistively-modulated light-emitting diodes, or ChemLEDs, that permit a simultaneous optical read-out in response to an analyte is obtained. The optical nose uses a common voltage source and ground for all sensing elements and thus eliminates the need for complex wiring of individual sensors. This optical nose contains one hundred ChemLEDs and generates unique light patterns in response to gases and their mixtures. Optical pattern recognition methods enable the quantitative prediction of the corresponding concentrations and compositions, thereby paving the way for massively parallel artificial olfactory systems. ChemLEDs open the possibility to explore demanding gas sensing applications, including in environmental, food quality monitoring, and potentially diagnostic settings.

In-fiber Mach-Zehnder interferometer as a promising tool for optical nose and odor prediction during the fermentation process.

In this paper, we present an in-fiber Mach-Zehnder interferometer (MZI) applied to coffee bean fermentation monitoring. Two MZIs, based on a combination of a fiber taper cascaded by a micro-tapered long-period fiber grating, were installed in a fermentation barrel to monitor the liquids and gases released during the fermentation process. During this process, a variety of odors arise due to the yeast activity and their classification is important to decide when to stop the fermentation process. In this work, we show that the in-fiber MZIs are good candidates for optical noses in this scenario.

An optical nose based on array of metal-doped carbon dots for identification of hazardous amines and assessing meat freshness

There is an obvious pressing demand for the sensitive and rapid, identification of toxic gases as environmental concerns. In this study, a facile approach for the detection and identification of amine solvents is reported. A colorimetric sensor array composed of different ninhydrin-mediated transition metal-doped carbon dots (TMCDs), deposited on a paper substrate, could sniff the odor of 29 different amines and accomplish their accurate identification. This analytical device generates a unique response pattern for each amine. Modeling the response data of the sensor array by linear discriminate analysis yields a discrimination accuracy of 94 % for the amines. Also, this method allows rapid quantification of ethylamine and isopropylamine in the concentration ranges of 0.008–1600 ppm and 0.05–828 ppm with detection limits of 1.4 ppb and 39 ppb, respectively, which are well below the immediately dangerous to life or health (IDLH) limit concentration for these amines. Interestingly, this sensor array provides discrimination between the isomers of some amines. Moreover, binary and ternary mixtures of amine solvents could be well recognized with this sensor. The application of the sensor array was tested for the assessment of the quality and freshness of some kinds of meat.

A Paper-Based Biomimetic Sensing Device for the Discrimination of Original and Fraudulent Cigarette Brands Using Mixtures of MoS2 Quantum Dots and Organic Dyes.

In this study, we investigated the combined effects of MoS2 QDs' catalytic properties and the colorimetric responses of organic reagents to create a sniffing device based on the sensor array concept of the mammalian olfactory system. The aim was to differentiate the volatile organic compounds (VOCs) present in cigarette smoke. The designed optical nose device was utilized for the classification of various cigarette VOCs. Unsupervised Principal Component Analysis (PCA) and supervised Linear Discriminant Analysis (LDA) methods were employed for data analysis. The LDA analysis showed promising results, with 100% accuracy in both training and cross-validation. To validate the sensor's performance, we assessed its ability to discriminate between five cigarette brands, achieving 100% accuracy in the training set and 82% in the cross-validation set. Additionally, we focused on studying four popular Iranian cigarette brands (Bahman Kootah, Omega, Montana Gold, and Williams), including fraudulent samples. Impressively, the developed sensor array achieved a perfect 100% accuracy in distinguishing these brands and detecting fraud. We further analyzed a total of 126 cigarette samples, including both original and fraudulent ones, using LDA with a matrix size of (126 × 27). The resulting LDA model demonstrated an accuracy of 98%. Our proposed analytical procedure is characterized by its efficiency, affordability, user-friendliness, and reliability. The selectivity exhibited by the developed sensor array positions it as a valuable tool for differentiating between original and counterfeit cigarettes, thus aiding in border control efforts worldwide.

A miniaturized all-in-one optical nose based on 3D printing technology and patterned paper substrate for discrimination of volatile organic compounds

Herein, an integrated design of a paper-based colorimetric sensor array, which includes both sensor array and sampling vessel is described. The paper substrate was patterned for providing hydrophobic barriers to deposit sensing elements, while a hydrophilic regions were embedded on the paper for sample solution. In this way, the paper substrate works as a sensing device and sampling vessel, simultaneously. A miniaturized cubic reaction chamber sizing (30 × 30 × 0.02) mm, equipped with a small aperture for sample injection was fabricated using 3D printing technology to hold the paper substrate. The required sample volume was lowered down dramatically (13.0 μL) due to the all-in-one sampling and sensing device. This miniaturized sensor array concept was employed to detect and discriminate volatile organic compounds (VOCs) relating to different solvent families that are known as cancer biomarkers. A colorimetric sensor array was fabricated by spotting 12 indicators belonging to three families of solvatochromic dyes, pH indicators and metallochromic dyes. This simple proposed device was able to discriminate the studied solvents into three chemical families including polar protic, dipolar aprotic and nonpolar with 93% accuracy. In addition, this sensor showed potential for quantitative and semi-quantitative analysis of volatile compounds in their mixtures. In total, the designed device is portable, rapid, and cost-effective and requires low volumes of samples that can be considered a good candidate for various VOC analysis with limited volume.

Peptide-Encapsulated Single-Wall Carbon Nanotube-Based Near-Infrared Optical Nose for Bacteria Detection and Classification

Sense of smell has been used as a diagnostic tool for almost entire human history. While successful examples of the use of the human nose for diagnostics are rare in modern history, there are ample reports of use of animals to diagnose various medical conditions. Bacterial infections often result in strong odors. In recent years, electronic noses (e-nose) and optical noses (o-nose) are of high interest in diagnostics and classification of bacterial infections. Artificial olfactory sensors can perform noninvasively, immediately at the point of care, do not require extensive sample handling, and promise to be highly cost-effective. This manuscript demonstrates the development of a near-infrared optical sniffer comprised of peptide-encapsulated (6,5) single-wall carbon nanotubes (SWCNTs) for bacteria detection and classification. Sixteen different peptides that include tyrosine in different proportions and positions were synthesized. The ability of these peptides to disperse SWCNTs in water was tested, and the intensity of the resultant optical signal was evaluated. Overall, longer peptides provided better dispersion as compared to shorter peptides. Addition of the fluorenylmethyloxycarbonyl chloride (Fmoc) group to positively charged peptides tested in the current study significantly improved SWCNT dispersion and signal intensity. The sensors successfully distinguished between the odor of sterile growth medium, Escherichia coli, and Klebsiella pneumoniae. Moreover, we demonstrated the possibility of using the developed sensors for antibiotics susceptibility testing. The sensors provided results in real-time, enabled multiple-usage, and operated at room temperature.

Paper-Based Optical Nose Made with Bimetallic Nanoparticles for Monitoring Ignitable Liquids in Gasoline.

A paper-based optical nose was fabricated by dropping bimetallic silver and gold nanoparticles on a paper substrate. The nanoparticles were synthesized by both natural (lemon, pomegranate, and orange juices) and chemical (citrate, gallic acid, and ascorbic acid) reducing agents. The performance of the assay was evaluated for identifying gasoline and five ignitable liquids such as diesel, ethanol, methanol, kerosene, and thinner. The interaction of the sensor with sample vapors caused aggregation, consequently changing the color of nanoparticles. The color changes, which were captured by a scanner, represented a specified colorimetric map for each analyte, allowing one to identify the studied fuels. The visual results were confirmed using multivariate statistical analysis such as principal component analysis and hierarchical clustering analysis. Also, partial least-squares regression was used to assist the proposed assay for estimating the amount of studied ignitable liquids as counterfeit species in the gasoline sample. The root-mean-square errors for prediction were 3.4, 2.1, 1.9, 2.0, and 1.7% for diesel, thinner, kerosene, ethanol, and methanol, respectively. Finally, the fabricated sensor indicated high efficiency for the on-site detection of pure industrial gasoline samples from adulterated ones.

Halochromic optical nose for assessment of spoilage of packed seer fish (II): leaching resistance, correlation between halochromism and volatile amines

PurposeDevelopment of thin film sensors with pH function for noninvasive real-time monitoring of spoilage of packed seafood such as fish, crab and shrimp are described in this study. It is also the purpose of this study to enhance the leaching resistance of the sensors by using a suitable strategy and to quantitatively correlate the sensor’s halochromism with the total volatile amine.Design/methodology/approachTo prepare halochromic sensors with better leaching resistance, biocompatible materials such as starch, agar, polyvinyl alcohol and cellulose acetate along with a halochromic dye were used to prepare the thin film sensors. These thin films were evaluated for monitoring the spoilage of packed seafood at room temperature, 4°C and −2°C up to 30 days. The halochromic sensors were characterized using UV-visible and FT-IR spectroscopy.FindingsCIELab analyses of the halochromism of the thin film sensors revealed that the color changes exhibited by the sensors in response to the spoilage of seafood are visually distinguishable. Further, the halochromic response of the thin films was directly proportional to the amount of total volatile base nitrogen that evolved from the packed seafood. Excellent leaching resistance was observed for the developed thin film sensors. The halochromic property of the sensors is reversible and thus the sensors are recyclable. Besides, the thin film sensors exhibited significant biodegradability.Originality/valueThis study provides insights for use of different biocompatible polymers for obtaining enhanced leaching resistance in halochromic sensors. Further, the color changes exhibited by the sensors are in line with the total volatile amines evolved from the packed seafood. These results highlight the importance of the developed halochromic thin film sensors for real-time monitoring of the spoilage of packed seafood.

Halochromic optical nose for assessment of spoilage of packed seer fish

PurposeThe present study aims to describe the development of halochromic thin film sensors using mixed indicator dyes for monitoring the spoilage of packed seer fish.Design/methodology/approachThin film was prepared using renewable polysaccharide incorporated with mixed indicator dyes. The thin film was characterized using ultraviolet visible and Fourier transform-infrared spectroscopy. The characteristics of the thin film were studied by analyzing the CIELAB and Red Green Blue values and biodegradability. The thin films were evaluated for real-time monitoring of the spoilage of packed seer fish.FindingsThe thin film sensors were found to exhibit excellent halochromism. The color changes were visible and distinguishable. The sensors responded efficiently for real-time monitoring of spoilage of fish by showing unique color changes.Originality/valueThis study provides promising mixed indicator that exhibits different colors in the alkaline pH. Also the present study reveals a potential combination of materials for preparation of halochromic sensors that can be used for monitoring the spoilage of packed seer fish in real time.

A nanoscale paper-based near-infrared optical nose (NIRON)

Electronic noses (e-nose) and optical noses (o-nose) are two emerging approaches for the development of artificial olfactory systems for flavor and smell evaluation. The current work leverages the unique optical properties of semiconducting single-wall carbon nanotubes (SWCNTs) to develop a prototype of a novel paper-based near-infrared optical nose (NIRON). We have drop-dried an array of SWCNTs encapsulated with a wide variety of peptides on a paper substrate and continuously imaged the emitted SWCNTs fluorescence using a CMOS camera. Odors and different volatile molecules were passed above the array in a flow chamber, resulting in unique modulation patterns of the SWCNT photoluminescence (PL). Quartz crystal microbalance (QCM) measurements performed in parallel confirmed the direct binding between the vapor molecules and the peptide-SWCNTs. PL levels measured before and during exposure demonstrate distinct responses to the four tested alcoholic vapors (ethanol, methanol, propanol, and isopropanol). In addition, machine learning tools directly applied to the fluorescence images allow us to distinguish between the aromas of red wine, beer, and vodka. Further, we show that the developed sensor can detect limonene, undecanal, and geraniol vapors, and differentiate between their smells utilizing the PL response pattern. This novel paper-based optical biosensor provides data in real-time, and is recoverable and suitable for working at room temperature and in a wide range of humidity levels. This platform opens new avenues for real-time sensing of volatile chemical compounds, odors, and flavors.

A Sensitive “Optical Nose” for Detection of Volatile Organic Molecules Based on Au@MOFs Nanoparticle Arrays through Surface‐Enhanced Raman Scattering

AbstractSurface‐enhanced Raman scattering (SERS) is an effective technique for detecting toxic gas and volatile organic molecules (VOMs); however, recent SERS‐based gas sensors have disadvantages and lack an effective approach to capture toxic gas and insufficient reproducibility of SERS substrates. Herein, a facile strategy is developed to integrate metal‐organic frameworks with Au nanoparticle (NP) arrays to form Au@ZIF‐8 NP arrays, which can be used as an “optical nose” based on SERS to detect toxic VOMs with good reproducibility and sensitivity. Toluene as a target molecule is recognized at ppm levels by the Au@ZIF‐8 NP arrays in situ. And the analytical enhancement factor of Au@ZIF‐8 NP arrays for toluene is about 1.2 × 105. Importantly, this SERS substrate can also detect the 1‐butanol molecule, which provides an idea for designing a universal VOM sensor. In addition, the coating method of the ZIF‐8 shell can be extended to synthetize various NPs@ZIF‐8 core–shell composites, such as Au nanospheres@ZIF‐8, Au@Ag nanorods@ZIF‐8, PS microspheres@ZIF‐8, and Fe2O3 microellipsoids@ZIF‐8 composites.

Optical nose based on porous silicon photonic crystal infiltrated with ionic liquids

A photonic-nose for the detection and discrimination of volatile organic compounds (VOCs) was constructed. Each sensing element on the photonic sensor array was formed by infiltrating a specific type of ionic liquid (IL) into the pore channel of a patterned porous silicon (PSi) chip. Upon exposure to VOC, the density of IL dramatically decreased due to the nano-confinement effect. As a result, the IL located in pore channel expanded its volume and protrude out of the pore channel, leading to the formation of microdroplets on the PSi surface. These VOC-stimulated microdroplets could scatter the light reflected from the PSi rugate filter, thereby producing an optical response to VOC. The intensity of the optical response produced by IL/PSi sensor mainly depends on the size and shape of microdroplets, which is related to the concentration of VOC and the physi-chemical propertied of ILs. For ethanol vapor, the optical response has linear relationship with its relative vapor pressure within 0–60%. The LOD of the IL/PSi sensor for ethanol detection is calculated to be 1.3 ppm. It takes around 30 s to reach a full optical response, while the time for recovery is less than 1 min. In addition, the sensor displayed good stability and reproducibility. Owing to the different molecular interaction between IL and VOC, the ILs/PSi sensor array can generate a unique cross-reactive “fingerprint” in response to a specific type of VOC analyte. With the assistance of image technologies and principle components analysis (PCA), rapid discrimination of VOC analyte could be achieved based on the pattern recognition of photonic sensor array. The technology established in this work allows monitoring in-door air pollution in a visualized way.

Detection of Volatile Organic Compounds Using Langmuir-Blodgett Films of Zinc-Porphyrin and Zinc-Phthalocyanine

Detection of volatile organic compounds (VOCs) by electronic optical nose based on sensing thin films is becoming more interesting in modern industry and daily life. The thin films of zinc-porphyrin and zinc-phthalocyanine fabricated by Langmuir-Blodgett (LB) technique onto quartz substrates have been used as sensing elements for electronic optical nose application. Absorption spectra range of the both organic elements in a chloroform solution and the LB solid state thin films were acquired by using a UV-1700 spectrometer. As an electronic gas sensing test, the optical absorbance performance after the exposure of LB films to different VOCs, and dry air was investigated. The results indicated that the ZnTPP and ZnPc LB films showed different gas sensitivity due to different molecule structure. Besides, a 2 × 1 colorimetric array is fabricated by immobilizing sensing thin film on a silica substrate, and the vapor molecules of pyridine and methanol can be easily detected.

Lipid Multilayer Grating Arrays Integrated by Nanointaglio for Vapor Sensing by an Optical Nose.

Lipid multilayer gratings are recently invented nanomechanical sensor elements that are capable of transducing molecular binding to fluid lipid multilayers into optical signals in a label free manner due to shape changes in the lipid nanostructures. Here, we show that nanointaglio is suitable for the integration of chemically different lipid multilayer gratings into a sensor array capable of distinguishing vapors by means of an optical nose. Sensor arrays composed of six different lipid formulations are integrated onto a surface and their optical response to three different vapors (water, ethanol and acetone) in air as well as pH under water is monitored as a function of time. Principal component analysis of the array response results in distinct clustering indicating the suitability of the arrays for distinguishing these analytes. Importantly, the nanointaglio process used here is capable of producing lipid gratings out of different materials with sufficiently uniform heights for the fabrication of an optical nose.

An Optical Nose Chip Based on Mesoporous Colloidal Photonic Crystal Beads

An optical nose chip is developed using surface functionalized mesoporous colloidal photonic crystal beads as elements. The prepared optical nose chip displays excellent discrimination among a very wide range of compounds, not only the simplex organic vapors from the different or same chemical family, but also the complex expiratory air from different people.

Pd-based integrated optical hydrogen sensor on a silicon-on-insulator platform

We have experimentally demonstrated a compact, integrated optical hydrogen sensor on a silicon-on-insulator platform. The sensor consists of silicon waveguide coated with a thin palladium film. The sensitivity and response time of the sensor was tested for volumetric hydrogen concentrations ranging from 0% to 4%. The proposed hydrogen sensor shows great potential as a building block for an optical nose capable of simultaneous detection of multiple gases as well as environmental effects such as temperature and humidity.

Corona discharge radical emission spectroscopy: a multi-channel detector with nose-type function for discrimination analysis

A simple and economical multi-channel optical sensor using corona discharge radical emission spectroscopy is developed and explored as an optical nose for discrimination analysis of volatile organic compounds, wines, and even isomers.

SERS substrate for detection of explosives

A novel gold coated femtosecond laser nanostructured sapphire surface - an "optical nose" - based on surface-enhanced Raman spectroscopy (SERS) for detecting vapours of explosive substances was investigated. Four different nitroaromatic vapours at room temperature were tested. Sensor responses were unambiguous and showed response in the range of 0.05-15 μM at 25 °C. The laser fabricated substrate nanostructures produced up to an eight-fold increase in Raman signal over that observed on the unstructured portions of the substrate. This work demonstrates a simple sensing system that is compatible with commercial manufacturing practices to detect taggants in explosives which can undertake as part of an integrated security or investigative mission.

Nanocomposite of Porous Silicon and Methylene Blue Molecules for Optical Gas Sensor Application

The present work reports the photoluminescence (PL) response of the porous silicon (PS)-methylene blue (MB) nanocomposite exposed to different organic solvents. In all the cases the PL intensity increased after gas injection. These results have been explained as a blinding effect of gas absorbed molecules, avoiding the non radiative paths. The PL responses spectra of the PL emission for different gases showed to be different patterns for each type of gases, suggesting that the PS-MB films could be applied for an optical nose system.