Detecting trace of mercury ions in water using photoacoustic method enhanced by gold nanospheres

Rapid and sensitive in situ detection of heavy metals in fish using enhanced Raman spectroscopy

Heavy metals have been widely applied in industry, agriculture, and other fields because of their outstanding physics and chemistry properties. They are non-degradable even at low concentrations, causing irreversible harm to the human and other organisms. Therefore, it is of great significance to develop high accuracy and sensitivity as well as stable techniques for their detection. Raman scattering spectroscopy and atomic absorption spectrophotometer (AAS) were used parallelly to detect heavy metal ions such as Hg, Cd, and Pb of different concentrations in fish samples. The concentration of the heavy metals is varied from 5 ppb to 5 ppm. Despite the satisfactory recoveries of AAS, their drawbacks are imperative for an alternative technique. In Raman scattering spectroscopy, the intensities and areas of the characteristic peaks are increased with increasing the concentration of the heavy metals. For Hg concentration ≥ 1 ppm, a slight shift is observed in the peak position. The obtained values of peak intensity and peak area are modeled according to Elvoich, Pseudo-first order, Pseudo-second order, and asymptotic1 exponential model. The best modeling was obtained using the Elovich model followed by the asymptotic1 exponential model. The introduced Raman spectroscopy-based approach for on-site detection of trace heavy metal pollution in fish samples is rapid, low-cost, and simple to implement, increasing its visibility in food safety and industrial applications.

Machine Learning Enabled Photoacoustic Spectroscopy for Noninvasive Assessment of Breast Tumor Progression In Vivo: A Preclinical Study

Breast cancer is a dreaded disease affecting women the most in cancer-related deaths over other cancers. However, early diagnosis of the disease can help increase survival rates. The existing breast cancer diagnosis tools do not support the early diagnosis of the disease. Therefore, there is a great need to develop early diagnostic tools for this cancer. Photoacoustic spectroscopy (PAS), being very sensitive to biochemical changes, can be relied upon for its application in detecting breast tumors in vivo. With this motivation, in the current study, an aseptic chamber integrated photoacoustic (PA) probe was designed and developed to monitor breast tumor progression in vivo, established in nude mice. The device served the dual purpose of transporting tumor-bearing animals to the laboratory from the animal house and performing PA experiments in the same chamber, maintaining sterility. In the current study, breast tumor was induced in the nude mice by MCF-7 cells injection and the corresponding PA spectra at different time points (day 0, 5, 10, 15, and 20) of tumor progression in vivo in the same animals. The recorded photoacoustic spectra were subsequently preprocessed, wavelet-transformed, and subjected to filter-based feature selection algorithm. The selected top 20 features, by minimum redundancy maximum relevance (mRMR) algorithm, were then used to build an input feature matrix for machine learning (ML)-based classification of the data. The performance of classification models demonstrated 100% specificity, whereas the sensitivity of 95, 100, 92.5, and 85% for the time points, day 5, 10, 15, and 20, respectively. These results suggest the potential of PA signal-based classification of breast tumor progression in a preclinical model. The PA signal contains information on the biochemical changes associated with disease progression, emphasizing its translational strength toward early disease diagnosis.

Experimental Research on Measuring the Concentration of CO2 in Gas-Liquid Solution Based on PZT Piezoelectric-Photoacoustic Spectroscopy

The feasibility of a scheme in which the concentration of CO2 in gas-liquid solution is directly measured based on PZT piezoelectric-photoacoustic spectroscopy was evaluated. The existing device used for the measurement of gas concentration in gas-liquid solution has several limitations, including prolonged duration, loss of gas, and high cost due to the degassing component. In this study, we developed a measuring device in order to solve the problems mentioned above. Using this device, how the intensity of the photoacoustic signal changes with the concentration of CO2 was demonstrated through experiment. The impact that variation of the laser modulation frequency has on the photoacoustic signal was also studied. Furthermore, the experimental data generated from measuring the concentration of CO2 in gas-liquid solution was verified for a wide range of concentrations. It was found that, not only can the error rate of the device be less than 7%, but the time of measurement can be within 60 s. To sum up, the scheme is highly feasible according to the experimental results, which makes measurement of the concentration of a gas in gas-liquid solution in the future more straightforward.

A potent multifunctional MnS/Ag-polyvinylpyrrolidone nanocomposite for enhanced detection of Hg2+ from aqueous samples and its photocatalytic and antibacterial applications

The development of nanotechnology for hazardous heavy metal detection with nanoparticles (NPs) created an interest for the preparation of MnS/Ag nanocomposite. Here, MnS/Ag-polyvinylpyrrolidone (PVP) nanocomposite was developed for the detection of mercury. The prepared composite was analyzed using particle size analyzer, X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Ultraviolet-visible (UV-vis) spectroscopy, zetasizer, high resolution transmission electron microscope (HRTEM) and Fourier-transform infrared spectroscopy (FTIR). The λ_max of MnS/Ag-PVP nanocomposite was observed at 404 nm. The particle size was determined to be 21 ± 1.7 nm and the surface charge was -31.19 ± 3 mV. The brownish yellow colour of the nanocomposite changed into colourless when Hg²⁺ was added. The different metal ions present with the analyte did not show any interference on detection of Hg²⁺. The MnS/Ag-PVP nanocomposite incorporated paper and gel exhibited visual detection of Hg²⁺ from aqueous sample. There was an excellent linearity (y = -0.0015x + 0.8744) found in plot of 20 to 100 nM Hg²⁺ concentrations versus absorbance at 404 nm and the LOD was calculated to be 16 nM. The probe was applied to quantify Hg²⁺ from spiked environmental sample and the results were further confirmed with atomic absorption spectrophotometric analysis. Hence, the investigation suggests that the present probe could efficiently detect and quantify Hg²⁺ at nano molar level. In addition, the study suggests that MnS/Ag-PVP nanocomposite exhibit multifunctional property including efficient photocatalytic and antimicrobial activity. The antibacterial activity was evaluated against both gram positive and gram negative bacteria.

Development of a Low-Cost UV-Vis Spectrophotometer and Its Application for the Detection of Mercuric Ions Assisted by Chemosensors

Detection of an environmental contaminant requires the use of expensive measurement equipment, which limits the realization of in situ tests because of their high cost, their limited portability, or the extended time duration of the tests. This paper presents in detail the development of a portable low-cost spectrophotometer which, by using a specialized chemosensor, allows detection of mercuric ions (Hg²⁺), providing effective and accurate results. Design specifications for all the stages assembling the spectrophotometer and the elements selected to build them are presented along with the process to synthesize the chemosensor and the tests developed to validate its performance in comparison with a high-precision commercial laboratory spectrophotometer.