Usage Of Spectroscopy In Managing Optical Sensors Manufacturing For Hazardous Emission Detection

INTRODUCTION

Spectroscopy is essential in the manufacturing and operation of optical sensors designed to monitor hazardous emissions. These sensors are crucial for environmental safety, regulatory compliance, and industrial monitoring. During manufacturing, spectroscopy ensures the precise characterization of materials, including the thickness and purity of thin films used in sensors. It plays a vital role in calibrating sensors, ensuring accurate wavelength detection and response to various gas concentrations. Spectroscopic techniques also facilitate real-time, in-situ monitoring of the manufacturing process, enhancing quality control by verifying that sensors meet required specifications.

In operation, these sensors rely on spectroscopic principles to detect and measure hazardous gases like NOx, SOx, and VOCs by identifying their unique spectral signatures. Advanced data analysis further optimizes sensor performance, improving sensitivity and selectivity. Spectroscopy ensures that sensors are accurate and reliable, helping industries comply with environmental regulations and safeguarding public health. Overall, spectroscopy is integral to the development and deployment of optical sensors that protect the environment and human health by providing precise monitoring of harmful emissions.

METHODOLOGY

 Process monitoring is a critical component of quality control that involves continuously observing and analyzing production processes to ensure they operate within defined parameters. It helps detect deviations or inefficiencies in real-time, allowing for immediate corrective actions to prevent defects and maintain product quality. This practice is vital in industries where consistency and precision are crucial, such as manufacturing, pharmaceuticals, and food production.

Advanced tools like sensors, automated systems, and data analytics are commonly used in process monitoring to track variables such as temperature, pressure, and chemical composition. By maintaining these variables within set limits, process monitoring helps optimize production efficiency, reduce waste, and ensure that the final product meets quality standards. Additionally, process monitoring contributes to predictive maintenance by identifying potential issues before they lead to equipment failure, thereby minimizing downtime and enhancing overall productivity.

APPLICATION

“Application of Raman spectroscopy to working gas sensors: from in situ to operando studies” is a typical example that clearly shows how spectroscopy works in managing manufacturing processes of gas sensors.

Raman spectroscopy, which can generally determine features of the sensors based on the characteristics of detecting vibration in the sensors or synthesis environment. In these studies, typical gas sensor materials, such as SnO2, WO3, and In2O3 were investigated towards a variety of target gases including exhausted gases such as H2S, CO, NH3, NO2, and others (CH4, H2, ethanol (EtOH), and acetaldehyde (acetald.)).

Spectroscopy on Gas Sensors

Figure 1a indicates the dominance peaks of SnO2 at 618 cm⁻¹, surface modes between 450 and 700 cm⁻¹ and a signal at 990 cm⁻¹, which is proposed to be caused by the presence of SO42− ions. Raman spectrum intensity decreases and a broad band, at around 350 cm⁻¹ After switching to H2S atmosphere. Figure 1b shows depicts the changes in the Raman intensity of the bands at 960 and 1600 cm⁻¹. The surface with carbon species during CH4 exposure leads to a decrease in the intensity of the 960 cm⁻¹ mode.

In this review we summarized the impact of vibrational Raman spectroscopy on deepening our mechanistic understanding of working metal-oxide gas sensors by starting from initial In situ applications to the current state of knowledge using multiple operando spectroscopic approaches. As discussed above, Raman spectroscopy can be applied to a wide range of sensor materials revealing valuable information on the (sub)surface structure, including hydroxyl groups and the presence of adsorbates.

Figure 1. a) In situ Raman spectra of a SnO2 pellet during exposure to two 300 ppm H2S-air cycles at 100 °C. b) Changes in the Raman intensity of the 960 (solid) and 1600 cm⁻¹ (dotted) bands of WO3 (2 nm particle size) during varying atmospheres.

EQUIPMENT

There are some kinds of methods using spectroscopy to monitor the sensor-producing process such as reflectance, absorbance, fluorescence, and Raman. Intins is glad to introduce to customers a comprehensive product set of Raman from Ocean Optic. The product set includes excitation lasers, spectrometers, Raman probes, sample holders for cuvettes, SERS substrates, and safety glasses. Moreover, Intins also provides software for calculating Raman signals and even custom software following customers’ desires. The customers can buy whole the system of Raman as Intins recommended, or chose any product that suit for their setups.

Spectrometer

Currently, there are two spectrometer lines are used for Raman applications such as QE Pro-Raman+ and NIRQuest+1064 Raman. The QE Pro-Raman+  has the Raman shift at 4429 cm¯¹ (532 nm), 2820 cm¯¹ (638 nm), 3002 cm¯¹ (785 nm), the integration time is 8 ms – 3600 s, while the NIRQuest+1064 Raman are used for 2400 cm¯¹ (1064 nm).

Raman Laser

We offer high-power lasers at 532 nm, 638 nm, 785 nm, and 1064 nm Raman excitation wavelengths. These multimode diode lasers produce narrow spectral lines, have an integrated laser driver, and employ thermoelectric cooling for optimal performance.

Raman Probe

Probes for 532 nm, 785 nm, and other wavelengths, are suitable for both lab and industry.

Raman Holder

Ocean Optics offers sample holders for Raman analysis of liquids and solids. The RM-SERS-SHS holder accommodates a standard glass SERS substrate and attaches to a Raman probe. The RM-LQ-SHS holder holds vials and cuvettes. It has a magnetic lid that facilitates sample placement, blocks ambient light, and improves the accuracy of Raman measurements.

SERS substrates

Surface-enhanced Raman spectroscopy (SERS) substrates allow you to make fast, repeatable measurements to identify and quantify SERS active analytes. SERS active chemistry is gold (Au) and silver (Ag) nanoparticles. Its storage lifetime is 1 month or 1.5 months.