Sibasish Dutta

Evanescent Wave Coupled Spectroscopic Sensing Using Smartphone

This letter demonstrates a technique that utilizes the camera of a smartphone for evanescent wave coupled spectroscopic sensing. Using simple optical components, the camera of the smartphone is converted into a highly resolved spectrometer (0.305 nm per pixel), and using a right-angled glass prism, the evanescent field of the internally reflected light signal from a broadband optical source is allowed to interact with the external medium. The primary advantages of the proposed sensing technique are its compactness, portability, and cost-efficiency.

Smartphone based LSPR sensing platform for bio-conjugation detection and quantification

We report here the working of a localized surface plasmon resonance (LSPR) sensor using the camera of a smartphone. Integrating light weight and simple laboratory optical components with the camera module of the phone, we first designed a visible spectrophotometer with a pixel resolution of 0.336 nm per pixel. The LSPR peak absorption wavelength shift due to size variation of gold nanoparticles (AuNPs) and analyte (protein and enzyme) conjugation with AuNPs have been successfully recorded by our smartphone spectrophotometer. The shift in LSPR peak absorption wavelength can be correlated with the size of the AuNPs and concentration of biomolecules attached to it. The limit of detection (LOD) of the designed sensor for quantification of BSA protein and trypsin enzyme was estimated to be 19.2 μg mL−1 (equivalent to 0.28 μM) and 25.7 μg mL−1 (equivalent to 1.10 μM) respectively. We compare the results with a laboratory grade standard UV-VIS spectrophotometer and observe high reliability of our designed sensor. Owing to its compact size, simple optics design and involvement of low-cost optical components we envision that the proposed sensing system could emerge as an alternative inexpensive handheld LSPR sensing tool that can be suitable for different in-field applications.

Ground and river water quality monitoring using a smartphone-based pH sensor

We report here the working of a compact and handheld smartphone-based pH sensor for monitoring of ground and river water quality. Using simple laboratory optical components and the camera of the smartphone, we develop a compact spectrophotometer which is operational in the wavelength range of 400-700 nm and having spectral resolution of 0.305 nm/pixel for our equipment. The sensor measures variations in optical absorption band of pH sensitive dye sample in different pH solutions. The transmission image spectra through a transmission grating gets captured by the smartphone, and subsequently converted into intensity vs. wavelengths. Using the designed sensor, we measure water quality of ground water and river water from different locations in Assam and the results are found to be reliable when compared with the standard spectrophotometer tool. The overall cost involved for development of the sensor is relatively low. We envision that the designed sensing technique could emerge as an inexpensive, compact and...

Dye-Assisted pH Sensing Using a Smartphone

We report the working of a smartphone-based optical sensor for the measurement of pH level of colorless aqueous media. By integrating readily available laboratory optical components to the camera of the smartphone, we convert the smartphone into a visible spectrophotometer with spectral resolution of 0.345 nm/pixel. Evanescent light signal from the designed optical sensing setup is allowed to interact with a pH sensitive dye sample. The transmitted light signal from the sensing region is then captured by the camera of the smartphone in the form of modulated visible image spectrum. The designed sensor can detect change in pH level of medium with a resolution of 0.12 pH unit within range of 6-8 pH unit. We evaluate the repeatability of our sensor for eight consecutive trials and obtained a standard deviation

LSPR enhanced gasoline sensing with a U-bent optical fiber

\sim 0.015

Protein, enzyme and carbohydrate quantification using smartphone through colorimetric digitization technique

in the transmission intensity within range of 6-8 pH units. We envision that our designed sensing technique could emerge as a low cost, portable, and robust pH sensor that has the ability to measure pH level of colorless aqueous medium with good accuracy and repeatability.

A fully automated colorimetric sensing device using smartphone for biomolecular quantification

We report here a gasoline sensor utilizing localized surface plasmon resonance (LSPR) phenomenon of metal nanoparticles (NPs) with a U-bent optical fiber. The optical response of the noble metal NPs upon interaction with gasoline has been simulated and experimentally demonstrated. The increase in gasoline vapor over a period of time induces a change in the refractive index of the adjacent medium of nanoparticle colloids, adhering to the probe, and thus the variation has been observed accordingly. This change in the refractive index in the close proximity to noble metals NPs produces a measurable variation in the output signal that has been correlated with the increase in the concentration of gasoline. The sensor provides better sensitivity corresponding to AgNPs when compared to AuNPs. However, in terms of stability, AuNPs-based LSPR performs better than the AgNPs-based plasmonic response. The present sensing set-up offers a light weight, robust and easy to implement platform that has potent application in detecting volatile liquids very effectively.

Smartphone Based Platform for Colorimetric Sensing of Dyes

In this paper the utilization of smartphone as a detection platform for colorimetric quantification of biological macromolecules has been demonstrated. Using V-channel of HSV color space, the quantification of BSA protein, catalase enzyme and carbohydrate (using D-glucose) have been successfully investigated. A custom designed android application has been developed for estimating the total concentration of biological macromolecules. The results have been compared with that of a standard spectrophotometer which is generally used for colorimetric quantification in laboratory settings by measuring its absorbance at a specific wavelength. The results obtained with the designed sensor is found to be similar when compared with the spectrophotometer data. The designed sensor is low cost, robust and we envision that it could promote diverse fields of bio-analytical investigations. Schematic illustration of the smartphone sensing mechanism for colorimetric analysis of biomolecular samples.

LSPR based Ultra-sensitive low cost U-bent optical fiber for volatile liquid sensing

In the present work, the use of smartphone for colorimetric quantification of biomolecules has been demonstrated. As a proof-of-concept, BSA protein and carbohydrate have been used as biomolecular sample. BSA protein and carbohydrate at different concentrations have been treated with Lowrys reagent and Anthrones reagent respectively . The change in color of the reagent-treated samples at different concentrations have been recorded with the camera of a smartphone in combination with a custom designed optomechanical hardware attachment. This change in color of the reagent-treated samples has been correlated with color channels of two different color models namely RGB (Red Green Blue) and HSV (Hue Saturation and Value) model. In addition to that, the change in color intensity has also been correlated with the grayscale value for each of the imaged sample. A custom designed android app has been developed to quantify the bimolecular concentration and display the result in the phone itself. The obtained results have been compared with that of standard spectrophotometer usually considered for the purpose and highly reliable data have been obtained with the designed sensor. The device is robust, portable and low cost as compared to its commercially available counterparts. The data obtained from the sensor can be transmitted to anywhere in the world through the existing cellular network. It is envisioned that the designed sensing device would find wide range of applications in the field of analytical and bioanalytical sensing research.

Solvent treated paper resistor for filter circuit operation and relative humidity sensing

We demonstrate the working of a smartphone based optical sensor for measuring absorption band of coloured dyes. By integration of simple laboratory optical components with the camera unit of the smartphone we have converted it into a visible spectrometer with a pixel resolution of 0.345 nm/pixel. Light from a broadband optical source is allowed to transmit through a specific dye solution. The transmitted light signal is captured by the camera of the smartphone. The present sensor is inexpensive, portable and light weight making it an ideal handy sensor suitable for different on-field sensing.