Advances in imaging-assisted sensing techniques for heavy metals in water: Trends, challenges, and opportunities
Graphical abstract
Section snippets
Introduction: heavy metals and metalloids
The contamination of natural water resources by heavy metals and metalloids is a controversial subject due to the hazardous effects on human health through the disturbance of nutritional, ecological, and environmental systems. The cause of this contamination is the relatively high density of metal ions, which exhibit toxicity on accumulation. Under the Priority List of Hazardous Substances, jointly prepared by the Agency for Toxic Substances and Disease Registry and the US Environmental
Colorimetric sensors
Colorimetric detection is one of the most frequently employed signal transduction techniques. Although colorimetric judgment was performed initially with the naked eye, while in these days various readout devices have been introduced to maximize efficiency. Despite significant advancements, the technique remains at a nascent stage with respect to sensitivity and selectivity relative to fluorescent techniques. Further, this approach is based on either change in intensity or shifts in the
Roles of materials in imaging-based quantification
Over the years, various materials have been studied for imaging-based quantification of heavy metal ions, especially in a water matrix. In this section, we assign the materials to four major categories based on molecular structure and properties: organic ligands, metal nanoparticles, carbon quantum dots, and semiconductor quantum dots. Their roles in sensing various heavy metals discussed and summarized in Fig. 1. These two principles of colorimetric sensing were addressed by manipulating
Readout tools utilized in imaging-based quantification of heavy metals: working principle, advantages, and problems
Since ancient times, light has been a source of fascination. As a form of energy, its interactions with the world have been of great benefit to humanity. Human eyes are natural spectators of light's behavior, including reflectance, emittance, and scattering of the visible part of the electromagnetic spectrum. The spectral information captured processed by the brain and interpreted in terms of color, intensity, and depth perception. Advancements in colorimetric sensing with the aid of ubiquitous
Microfluidics in imaging-based sensors
Paper-based analytical devices make use of wicking properties of paper without requiring external power sources or equipment. Microfluidics is a promising strategy for the development of affordable and field-deployable sensors. One such candidate is the “lab on a chip” μPAD for sensing and detection applications [72]. The principle of μPADs is to configure paper substrates into two regions, i.e., hydrophobic barriers and hydrophilic channels. The primary advantage of microfluidics is control of
Role of substrates in imaging-based sensor
The efficacy of an imaging-based colorimetric sensor is determined not only by choice of materials (e.g., chemo-responsive dyes, organic ligands, metal nanoparticles, and quantum dots) but also the selection of substrate type and materials (e.g., the geometry of flow path and immobilization technique) [75]. Many substrates for colorimetric sensors are available, based on their nature and structure. The essential characteristics of substrates include optical transparency (owing to high
Mobile applications and kits for general water parameters quantification
The research domain of smartphones has grown considerably over the years, owing to their minicomputer operating systems and miniaturized hardware (e.g., cameras and antennas for networking). This section offers detailed insights into mobile apps used for the visualization of colorimetric assays of environmental pollutants, especially heavy metals. Correlation of the color intensity (e.g., RGB and grayscale) to heavy metal concentration is utilized to quantify heavy metal contamination. The
Performance comparison and future outlook
The development of a sensor system for heavy metals in natural waters remains a challenge in terms of various criteria such as effectiveness, efficiency, sensitiveness, selectiveness, user-friendliness, affordability, and field applicability. It is essential for understanding the fundamental role of sensor materials, imaging tools, substrates, software platforms, and sampling methods to realize such categories of sensing systems. Colorimetric sensors are one of the most promising options in
Conclusions
Worldwide concerns regarding the pollution of heavy metals in natural water resources have stimulated technological breakthroughs in the monitoring and removal of such targets. In the current era of rapidly advancing computational intelligence, digital solution methods employed in almost every sector of civil society, including health, manufacturing, diagnostics, defense, and personal security. Monitoring and sensor systems that take advantage of these technologies have also been proposed and
Acknowledgments
PD and AT acknowledge the financial support received from Department of Science and Technology under SEED grant (No.: SP/YO/126/2017) and DST-INSPIRE fellowship, respectively. RJ acknowledges the CSIR-Senior Research Fellowship by the Council of Scientific & Industrial Research (CSIR), India. Support and encouragement by Director, CSIR-CSIO is also acknowledged. KHK acknowledges support made in part by grants from the National Research Foundation of Korea funded by the Ministry of Science, ICT
References (98)
- et al.
Biosens. Bioelectron.
(2016) - et al.
Biosens. Bioelectron.
(2017) - et al.
Anal. Chim. Acta
(2017) - et al.
Anal. Chim. Acta
(2015) - et al.
Chemosphere
(2016) - et al.
Talanta
(2016) - et al.
Talanta
(2018) - et al.
Microchem. J.
(2018) - et al.
Sens. Actuators B: Chemical
(2018) - et al.
Sens. Actuators B Chem.
(2017)
Sens. Actuators B Chem.
Sens. Actuators B Chem.
Chem. Eng. J.
Chem. Eng. J.
Chin. Chem. Lett.
Talanta
Sens. Actuators B Chem.
Biosens. Bioelectron.
Sens. Actuators B Chem.
Biosens. Bioelectron.
Sens. Actuators B Chem.
Appl. Surf. Sci.
Sens. Actuators B Chem.
Sens. Actuators B Chem.
Anal. Chim. Acta
Sens. Actuators B Chem.
Water Res.
Sens. Actuators B Chem.
Mater. Sci. Eng. C-Mater. Biol. Appl.
ACS Sens.
Small
Anal. Bioanal. Chem.
Lab Chip
ACS Sustain. Chem. Eng.
ACS Appl. Mater. Interfaces
Anal. Bioanal. Chem.
Anal. Chem.
Anal. Chem.
Anal. Chem.
RSC Adv.
Analyst
Anal. Methods
Anal. Methods
Biomicrofluidics
Anal. Methods
Anal. Sci.
J. Braz. Chem. Soc.
Micromachines
Micromachines
Cited by (37)
Feasibility of digital image colorimetric methods for iron determination in river sediment
2024, International Journal of Sediment ResearchSimple colorimetric copper(II) sensor – Spectral characterization and possible applications
2023, Spectrochimica Acta - Part A: Molecular and Biomolecular SpectroscopyExploration and removal of multiple metal ions using mixed-linker-architected Zn-MOF in aqueous media
2023, Separation and Purification TechnologyCitation Excerpt :Lead poisoning in the body can damage the immune system, [4] cardiovascular [5] and also central nervous systems [6]. Due to high density and non-biodegradability, heavy metal ions lead to the formation of reactive oxygen species (ROS)[7] which causes various health effects such as oxidative stress[8], enzyme inhibition[9] and damage to nucleic acid and proteins[7]. Among heavy metal ions, Fe2+ plays an important role in biochemical processes such as electron transfer, DNA and RNA formation, storage and delivery of oxygen in the body but it can be toxic at high concentrations [10–13].
Small organic molecules as fluorescent sensors for the detection of highly toxic heavy metal cations in portable water
2023, Journal of Environmental Chemical Engineering