Present work demonstrates the operation of a smartphone platform sensor that accurately measures mercury (Hg (II)) level concentration in water. The sensing principle of the designed sensor is based on the detection of fluorescence emission from a ternary complex containing different concentration of Hg (II) in the mixture. The designed sensor correlates the level of Hg (II) concentration in a given sample through the emission of fluorescence emission from it. Using simple optical components, a compact optical set-up has been designed which can be attached to the rear-camera of the smartphone. Using the designed smartphone sensor Hg (II)-level variation as low as 50ppb can be detected accurately and reliably. The performance of the sensor has been evaluated in presence of other interfering elements such as iron, copper, zinc and manganese and we noticed that the sensor characteristic does not perturb by the presence of such elements. It has been observed that the proposed sensor performs at par with that of a laboratory grad optical spectrometer. Owing to the involvement of low-cost components and user-friendly application that essentially converts the CMOS illumination reading into a readable form we envision that the proposed sensing technique would be useful for in-field based sensing of Hg(II) level in water largely present in industrial waste water and other environmental water bodies.
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 Lowry's reagent and Anthrone's 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.
In the present work an all-fiber optic confocal microscope with submicron depth resolution is reported. The operation of the
microscope is based on the principle of back reflectance of propagated light from the target in a curve-shaped step-index
multimode optical fiber. Modulation of the back-reflected light with axial displacement of the target is monitored using a
photodiode (PD). The advantage of the system is its simplicity and possibility of remote monitoring. An axial displacement of
minimum 0.5 μm can be detected within the focusing depth with the present work.
We report a simple approach to measure relative humidity with high dynamic range and fast response time using
Cobalt chloride (CoCl2) doped polymer thin film. Anhydrous Cobalt chloride exhibits high absorption at low humidity
level in the wavelength range 550-700 nm while possess very low absorption at high humidity level present in
the environment. Thin CoCl2 doped polymer films of different thickness were fabricated on thin cover slides using dip
coating technique. Expanded light from a diode laser source (680 nm) was allowed to transmit through the sensing
film of the slide. The variation in intensity of the transmitted light with the moisture level present in the environment
was monitored using silicon photodiode and finally the detector signal was taken through a computer. As large area of
the sensing region is exposed to the environment, high sensitivity of the sensor is achieved. Further, sensor response was
investigated in terms of chemically synthesized film thickness on the slides. A high dynamic range of the sensor is
obtained with fully reversible and repeatable behavior. The advantage of the system is its simplicity and is a very low
cost technique to monitor relative humidity present in environment.
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