Eosin-Y containing electrospun fibers for optical ammonia sensing based on wavelength shift

Sensors in recent days have been in great demand in industrial zones of simple, low-cost sensors for effectively sensing various gases. This research work develops electrospinning fibers for optical ammonia sensing based on the wavelength shift. The optical sensing fibers were produced approach by the electrospinning technique. The addition of cellulose acetate (CA) matrix with doped Eosin-Y is an NH3 fluorophore. The same light emitting diode (LED) light source was used to excite NH3-sensitive dyes at 380 nm peak wavelength. Display the eosin Y emission spectrum, with a maximum wavelength of 582 nanometers. The observed red emission wavelength shift and fluorescence intensity at 582 nm decreased with increasing concentrations of NH3. The emission spectrum of eosin-Y fluorescence at 582 nanometers is changed with increasing NH3 concentrations ranging from 0 to 500 parts per million. In this work, according to the experiment results, the sensitivity of NH3 sensors is 7.73. Finally, the electrospinning fibers for optical NH3 sensing developed as a result of this research enable effective sensing of NH3 concentrations in practical applications in a variety of fields, including medical and industrial.


Introduction
In recent years, the novel gas sensor has been invented and developed, as well as advances have been made in areas like environmental analysis, manufacturing, medical application, and the quality of indoor air control.[1,2].A device used to detect the presence of a gas mixture in an area where it is hazardous, especially for humans and animals, is a gas sensor [3].Such gas detection is required to maintain ideal conditions for industrial applications and to warn of potentially hazardous conditions for health safety [4,5].It is becoming increasingly important for human well-being to monitor and the management of air pollutants, toxic gases, and explosives.Toxic gas detection, such as ammonia detection, is critical for industrial, laboratory, food storage, health monitoring, and safety purposes [6,7].Concerns regarding the environment and human health are growing.The detection of ammonia gas has gained considerable interest in the field of gas sensors, which is significant since Ammonia is among the most frequently produced and used chemical materials all over the globe [8][9][10][11][12][13][14].NH 3 gas is likewise a highly hazardous gas.On low concentrations of less than 50 ppm (mg/L), it causes irritation to the respiratory system, skin of the body, and eyes.While at about 500 ppm, it causes severe nasal and throat irritation as well as pulmonary edema.NH 3 is the most significant example of such a gas in terms of technology [15].Because of the harmful effects of ammonia on human health at low concentrations, a sensitive and rapid method for determining ammonia is compulsory [16].Sensors have parameters that are sensitivity, selectivity, stability, and recovery [17,18].Sensors that use fluorophores typically have higher sensitivity.Several parameters, as well as fluorescence quenching, decay time, polarization, and transfer of energy, can be measured simultaneously using optical sensors to achieve specific results [19].Fluorescent sensors are currently the most popular optical sensor.The main benefits of using fluorophores in measuring the optical properties of sensing materials are due to the instantaneous reaction and high single-molecule sensitivity.Furthermore, fluorescent dyes can be combined with various polymer matrices, which can improve their sensitivity, stability, and response time due to micro-nanofiber membrane properties like high porosity and large surface area [20].Electrospinning has gained popularity as a method for preparing nanomaterials because it is a low-cost, multipurpose, simple, and advanced process.Electrospinning is a technique that uses electric force to spin polymer, ceramic, and graphite fibers to form a Taylor cone.The resulting fiber is called electrospun.Fiber diameters range from 10 to 100 nanometers.Several parameters govern the electrospinning process, including flow rate, voltage, distance, viscosity, conductivity, and solution of the polymer.Each parameter affects the surface of the electrospun fiber during the Taylor cone forming process significantly, with the precise parameters, the polymer that forms the Taylor cone will produce the desired nanofiber surface morphology obtainable [21].
Table 1.Comparison of the optical sensor of ammonia sensing.
The optical parameters for ammonia sensing materials are shown in Table 1.Previously, several researchers have presented single and double-layer methods for fluorescence intensity and linearity.In this study, we have presented a novel and simple ammonia-sensing technique according to the wavelength shift and fluorescence quenching of a single fiber.Wherein Eosin Y is embedded in cellulose acetate as an ammonia indicator, the optical sensing method uses electrospinning, where the result of electrospinning is in the form of fiber and then tested using ammonia gas sensing.The electrospinning fibers for optical NH 3 sensing developed as a result of this research enable the effective sensing of NH 3 concentrations in practical applications in various fields, like medical, environmental, and manufacturing.

Experiment 2.1. Materials
The following materials were used without any purification.

Experimental
To prepare the ammonia-sensitive dye solution needed as a support matrix, 0,375-gram cellulose acetate (CA) powder was dissolved in a 2:1 mixture of 2 ml acetone and 1 ml DMAc solution.At room temperature, the solution was stirred for 1 hour.After that add 0,036 mg Eosin Y for ammoniasensitive dye solution and put the solution in the ultrasonic machine for 30 minutes.To achieve a balanced solution, we put again the solution the stirred it for 1 hour at room temperature.The finished solution will be made into fiber using the electrospinning technique approach.Finally, as sensing ammonia dye, the fiber was produced using an electrospinning machine.
The scanning electron microscope image is shown in Figures 1(a) and (b).Ammonia-sensing dyes have been coated onto the single fiber's surface and the EDS spectrum analysis results from the single fiber.EDS shows what elements are contained in this fiber.The samples for SEM measurement can be seen as the morphology of the single fiber with magnification x5000.This result of image SEM is uniform and there are no droplets.
(a) (b) Figure 1.Electrospun fibers of (a) SEM image at a resolution of x5000 and (b) EDS spectrum analysis.

The Instrumental
The gas sensing schematic illustration experimental design for detecting optical ammonia sensing performance is shown in Figure 2. In the interest of performing optical ammonia-sensing experiments, an LED (NSHU591B, NICHIA, COPR) light source with a central wavelength of 380 nanometers is excited by a waveform generator (TGA1240, Thurlby Thandar Instruments (TTI) Ltd.) with a frequency of 100 Hz in pulse signal mode and an amplitude of 5.The ammonia tested varies.A mass flow regulator is used to modify the concentration by mixing pure ammonia and nitrogen (Aalborg Instruments and Controls Inc, Orangeburg, NY, USA, Model GFC 17).Fluorophore absorption spectroscopy was obtained using a UV-VIS spectrophotometer.A USB 4000 spectrometer was used to measure emissions (Ocean Optics) [22,23].

Results and discussion
Figure 3 shows the ammonia sensing results obtained from the gas sensing experiment.After the single fiber sensor is excited by a 380 LED light source, by gradually opening the ammonia gas from 0-500 parts per million of concentration, ammonia sensing data is obtained.Figure 3 shows the process of how ammonia gas affects the ammonia sensing signal at 582 nm to gradually lower its emission peak upon exposure to ammonia from 0-500 ppm.It can be seen from the trend of wavelength shift when the ammonia concentration increases.As a result of these findings, it can be concluded that a single sensing device can be used as an ammonia-sensitive sensing device.Figure 4 demonstrates the presence of ammonia gas affected the emission peak of the ammonia sensing signal.Figure 4 shows a Stern-Volmer plot diagram of I 0 /I vs ammonia gas concentrations to prove the sensitivity of eosin Y deserves to propose as good sensing, where I 0 /I represent the steadystate luminescence intensities in the absence and presence of ammonia.As seen in Figure 4, the maximum sensitivity of eosin Y is 7.73 after exposure to 500 ppm ammonia.This sensing device can be concluded to be effective as an ammonia sensing probe in single sensing applications.Figure 5 shows the normalized fluorescence intensity with a shift in wavelength.Figure 5 shows normalized fluorescence intensity between wavelength shift.Figure 5 illustrates the optical sensing wavelength shift of ammonia subjected to NH 3 gas in a stepwise manner from 0-500 ppm.In the figure the trend has decreased in peak intensity after being exposed to ammonia gas, eosin Y also experienced a shift in wavelength.When the ammonia gas valve is opened at the desired concentration level, from 0 ppm to 500 ppm, the greater the wavelength shift will occur.Figure 6 shows changes in wavelength shift with increasing ammonia gas concentration.It can be seen from this trend that the greater the concentration of ammonia used, the farther the wavelength shift that occurs, the wavelength shift that occurs is 16 nm.This graph illustrates a plot of the calculation of the wavelength shift.Starting at 582 nm under room temperature, then increasing to 586 nm, 591 nm, 593 nm, and 596.40 nm after 100 to 500 ppm exposure.

Conclusion
In this study, the wavelength shift of the red emission was observed and the fluorescence intensity at 582 nm decreased with increasing NH 3 concentration.The fluorescence emission spectrum of eosin-Y at 582 nm changes with increasing ammonia gas concentration from 0 to 500 parts per million.In this work, an approach using an electrospinning technique to produce a novel single-fiber sensor to detect ammonia gas has been successfully developed by adding Eosin Y as a fluorescent dye.SEM measurements with EDS image spectrum analysis have been carried out and the SEM image results show that the fiber produced is uniform, well-formed, and there are no droplets.The experimental results show that the NH 3 sensor has a high sensitivity of 7.73 with a linearity of 0.97.Finally, the electrospinning fiber for optical NH 3 sensing developed as a result of this research enables effective sensing of NH 3 concentrations in practical applications in various fields, such as medical, environmental, and manufacturing.

Figure 2 .
Figure 2. Schematic diagram showing the experimental arrangement used for characterization.

Figure 5 .
Figure 5.The wavelength shift of ammonia-sensitive dye.

Figure 6 .
Figure 6.A plot of wavelength shift of ammonia sensing.