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Colorimetric Sensors: Methods and Applications (2nd Edition)
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Colorimetric Sensors: Methods and Applications (2nd Edition)

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Chemical Sensors".

Deadline for manuscript submissions: closed (28 February 2026) | Viewed by 12407

Special Issue Editors

Prof. Dr. Fengqing Yang

E-Mail Website
Guest Editor
School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China
Interests: preparation and applications of materials with enzyme-like activity; spectroscopic analysis; chromatographic analysis
Special Issues, Collections and Topics in MDPI journals
Dr. Liya Ge

E-Mail Website
Guest Editor
Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore 637141, Singapore
Interests: analytical and bioanalytical chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Colorimetric sensors have attracted considerable attention for many sensing applications due to the potential for rapid analysis, cost effectiveness, ease of use, simple detection systems, or even naked-eye observations. Currently, a number of colorimetric sensors have been developed for the sensing of small molecules, including cations, anions, and neutral species and essential cellular components related to human living systems in solutions and biological samples, as well as therapeutic and diagnostic applications. In this Special Issue, we will take particular interest in manuscripts that discuss the principles and mechanisms, fabrication methods, and relevant applications in various fields of colorimetric sensors. We invite authors to contribute original research and review articles that will stimulate more basic research on the development of colorimetric sensors.

Potential topics suitable for this Special Issue include, but are not limited to, the following: colorimetric sensing principles and mechanisms; nanomaterials for colorimetric (bio)sensors for biomedical applications; paper-based colorimetric sensors; colorimetric sensors toward cations, anions, and biomolecules; and colorimetric strips.

Prof. Dr. Fengqing Yang
Dr. Liya Ge
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • colorimetric sensors
  • paper-based colorimetric sensors
  • chemical sensors
  • biosensors
  • colorimetric strips
  • colorimetric sensing arrays

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Related Special Issue

Published Papers (6 papers)

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Research

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15 pages, 5666 KB  
Article
Biocompatible and Flexible Cellulose Film for the Reversible Colourimetric Monitoring of pH and Mg (II)
by Iva Karneluti, Deepak Joshy, Gerhard J. Mohr, Cindy Schaude, Matthew D. Steinberg and Ivana Murković Steinberg
Sensors 2026, 26(3), 880; https://doi.org/10.3390/s26030880 - 29 Jan 2026
Viewed by 600
Abstract
Novel colourimetric sensors are readily devised by combining multifunctional (nano)materials with miniature optoelectronic components. The demand to detect and monitor metal ions has resulted in the invention of new colourimetric sensing schemes, especially for use at the Point-of-Need (PoN). Nonetheless, the design of [...] Read more.
Novel colourimetric sensors are readily devised by combining multifunctional (nano)materials with miniature optoelectronic components. The demand to detect and monitor metal ions has resulted in the invention of new colourimetric sensing schemes, especially for use at the Point-of-Need (PoN). Nonetheless, the design of fully reversible optical materials for continuous real-time ion monitoring remains a bottleneck in the practical realisation of sensors. Magnesium ion is vital to physiological and environmental processes, but monitoring can be challenging, particularly in the presence of Ca2+ as a cross-sensitive interferent in real samples. In this work, a chromophore molecule Hyphan I (1-(2-hydroxy-5-ß-hydroxyethylsulfonyl-phenyl-azo)-2-naphthol) has been grafted onto a cellulose matrix with a simple one-pot vinylsulfonyl process, to form a transparent, biocompatible and highly flexible thin-film colourimetric magnesium ion sensing material (Cellulose Film with Hyphan-CFH). The CFH film has a pH response time of <60 s over the pH range 4 to 9, with a pKa1 = 5.8. The LOD and LOQ for Mg2+ at pH 8 are 0.089 mM and 0.318 mM, respectively, with an RSD = 0.93%. The CFH film exhibits negligible interference from alkaline and alkaline earth metals, but irreversibly binds certain transition metals (Fe3+, Cu2+ and Zn2+). The CFH material has a fast and fully reversible colourimetric response to pH and Mg2+ over physiologically relevant ranges without interference by Ca2+, demonstrating good potential for integration into microfluidic systems and wearable sensors for biofluid monitoring. Full article
(This article belongs to the Special Issue Colorimetric Sensors: Methods and Applications (2nd Edition))
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9 pages, 1717 KB  
Article
New Imaging Method of Mobile Phone-Based Colorimetric Sensor for Iron Quantification
by Ngan Anh Nguyen, Asher Hendricks, Emily Montoya, Amber Mayers, Diwitha Rajmohan, Aoife Morrin, Margaret McCaul, Nicholas Dunne, Noel O’Connor, Andreas Spanias, Gregory Raupp and Erica Forzani
Sensors 2025, 25(15), 4693; https://doi.org/10.3390/s25154693 - 29 Jul 2025
Cited by 2 | Viewed by 2485
Abstract
Blood iron levels are related to many health conditions, affecting hundreds of millions of individuals worldwide. To aid in the prevention and treatment of iron-related disorders, previous research has developed a low-cost, accurate, point-of-care method for measuring iron from a single finger-prick blood [...] Read more.
Blood iron levels are related to many health conditions, affecting hundreds of millions of individuals worldwide. To aid in the prevention and treatment of iron-related disorders, previous research has developed a low-cost, accurate, point-of-care method for measuring iron from a single finger-prick blood sample. This study builds upon that work by introducing an improved imaging method that accurately reads sensor images irrespective of variations in environmental illumination and camera quality. Smartphone cameras were used as analytical tools, demonstrating an average coefficient of variation of 5.13% across different phone models, and absorbance results were found to be improved by 8.80% compared to the method in a previous study. The proposed method successfully enhances iron detection accuracy under diverse lighting conditions, paving the way for smartphone-based sensing of other colorimetric reactions involving various analytes. Full article
(This article belongs to the Special Issue Colorimetric Sensors: Methods and Applications (2nd Edition))
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20 pages, 6953 KB  
Article
Optimization of Dye and Plasticizer Concentrations in Halochromic Sensor Films for Rapid pH Response Using Bird-Inspired Metaheuristic Algorithms
by Daeuk Kim, Ronnie S. Concepcion II, Joseph Rey H. Sta. Agueda and Jubert C. Marquez
Sensors 2025, 25(11), 3494; https://doi.org/10.3390/s25113494 - 31 May 2025
Cited by 1 | Viewed by 1548
Abstract
The pH level of a wound environment is a crucial biomarker for monitoring wound healing, particularly in chronic wounds, where alkalinity (pH > 7) is linked to bacterial colonization and infection. This study developed and optimized a halochromic sensor film composed of polyvinyl [...] Read more.
The pH level of a wound environment is a crucial biomarker for monitoring wound healing, particularly in chronic wounds, where alkalinity (pH > 7) is linked to bacterial colonization and infection. This study developed and optimized a halochromic sensor film composed of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and bromothymol blue (BTB) to enable rapid and reliable pH-responsive color transitions. Feature selection using Principal Component Analysis (PCA) and the ReliefF algorithm identified Hue, Saturation, and a as key features influencing pH responsivity. Optimization of BTB (0.01–0.05%) and PEG (6–10%) concentrations was conducted using bird-inspired metaheuristic algorithms, including the Parrot Optimizer (PO), Pelican Optimization Algorithm (POA), and Secretary Bird Optimization Algorithm (SBOA). While final fitness values showed negligible variation (188.595647 for GP-PO, 188.595634 for GP-POA, and 188.595634 for GP-SBOA), GP-PO demonstrated superior convergence and stability, efficiently identifying the optimal formulation (0.02% BTB, 6% PEG). The optimized film achieved a complete color transition within 3–5 min, a 23.15% reduction compared to the non-optimized formulation. Statistical analysis revealed that BTB concentration significantly affected response time (p = 0.01), while PEG concentration had no significant effect (p > 0.05). These findings highlight the potential of halochromic films for real-time, non-invasive pH monitoring in chronic wounds. Full article
(This article belongs to the Special Issue Colorimetric Sensors: Methods and Applications (2nd Edition))
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16 pages, 6282 KB  
Article
Color QR Codes for Smartphone-Based Analysis of Free Chlorine in Drinking Water
by María González-Gómez, Ismael Benito-Altamirano, Hanna Lizarzaburu-Aguilar, David Martínez-Carpena, Joan Daniel Prades and Cristian Fàbrega
Sensors 2025, 25(11), 3251; https://doi.org/10.3390/s25113251 - 22 May 2025
Cited by 1 | Viewed by 2362
Abstract
Free chlorine (FC) plays a crucial role in ensuring the safety of drinking water by effectively inactivating pathogenic microorganisms. However, traditional methods for measuring FC levels often require specialized equipment and laboratory settings, limiting their accessibility and practicality for on-site or point-of-use monitoring. [...] Read more.
Free chlorine (FC) plays a crucial role in ensuring the safety of drinking water by effectively inactivating pathogenic microorganisms. However, traditional methods for measuring FC levels often require specialized equipment and laboratory settings, limiting their accessibility and practicality for on-site or point-of-use monitoring. QR Codes are powerful machine-readable patterns that are used worldwide to encode information (i.e., URLs or IDs), but their computer vision features allow QR Codes to act as carriers of other features for several applications. Often, this capability is used for aesthetics, e.g., embedding a logo in the QR Code. In this work, we propose using our technique to build back-compatible Color QR Codes, which can embed dozens of colorimetric references, to assist in the color correction to readout sensors. Specifically, we target two well-known products in the HORECA (hotel/restaurant/café) sector that qualitatively measure chlorine levels in samples of water. The two targeted methods were a BTB strip and a DPD powder. First, the BTB strip was a pH-based indicator distributed by Sensafe®, which uses the well-known bromothymol blue as a base-reactive indicator; second, the DPD powder was a colorimetric test distributed by Hach®, which employs diethyl-p-phenylenediamine (DPD) to produce a pink coloration in the presence of free chlorine. Custom Color QR Codes were created for both color palettes and exposed to several illumination conditions, captured with three different mobile devices and tested over different water samples. Results indicate that both methods could be correctly digitized in real-world conditions with our technology, rendering a 88.10% accuracy for the BTB strip measurement, and 84.62% for the DPD powder one. Full article
(This article belongs to the Special Issue Colorimetric Sensors: Methods and Applications (2nd Edition))
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18 pages, 3506 KB  
Article
Colorimetric 3D microPAD for Multiplexed Detection of Paracetamol and Aspirin in Urine and Saliva
by Alberto Abalde-Pujales, Vanesa Romero, Isela Lavilla and Carlos Bendicho
Sensors 2025, 25(6), 1756; https://doi.org/10.3390/s25061756 - 12 Mar 2025
Cited by 6 | Viewed by 3227
Abstract
In this work, a novel 3D μPAD cellulose-based colorimetric chemosensor for multiplexed detection of paracetamol and aspirin in biological samples is proposed. The easy availability of analgesics such as paracetamol and non-steroidal anti-inflammatory drugs such as aspirin, over-the-counter drugs that can be acquired [...] Read more.
In this work, a novel 3D μPAD cellulose-based colorimetric chemosensor for multiplexed detection of paracetamol and aspirin in biological samples is proposed. The easy availability of analgesics such as paracetamol and non-steroidal anti-inflammatory drugs such as aspirin, over-the-counter drugs that can be acquired without medical prescription, can entail a health problem if they are administered incorrectly. The development of analytical procedures for the rapid, sensitive, and accurate determination of such drugs in clinical samples is of utmost importance. Different parameters involved in the design of the 3D μPAD system and the colorimetric reaction conditions have been optimized. Under optimal conditions, detection limits of 0.004 mM and 0.013 mM were obtained for paracetamol and aspirin, respectively. The proposed procedure was validated against two certified reference materials and applied to the analysis of several synthetic urine and saliva samples. Synthetic urine and saliva samples were spiked at two concentration levels, showing recoveries in the range of 98–103% with a relative standard deviation of 3–6% (n = 6). Full article
(This article belongs to the Special Issue Colorimetric Sensors: Methods and Applications (2nd Edition))
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Review

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28 pages, 2805 KB  
Review
Emerging Trends in Artificial Intelligence-Assisted Colorimetric Biosensors for Pathogen Diagnostics
by Muniyandi Maruthupandi and Nae Yoon Lee
Sensors 2026, 26(2), 439; https://doi.org/10.3390/s26020439 - 9 Jan 2026
Viewed by 1028
Abstract
Infectious diseases caused by bacterial and viral pathogens remain a major global threat, particularly in areas with limited diagnostic resources. Conventional optical techniques are time-consuming, prone to operator errors, and require sophisticated instruments. Colorimetric biosensors, which convert biorecognitive processes into visible color changes, [...] Read more.
Infectious diseases caused by bacterial and viral pathogens remain a major global threat, particularly in areas with limited diagnostic resources. Conventional optical techniques are time-consuming, prone to operator errors, and require sophisticated instruments. Colorimetric biosensors, which convert biorecognitive processes into visible color changes, enable simple and low-cost point-of-care testing. Artificial intelligence (AI) enhances decision-making by enabling learning, training, and pattern recognition. Machine learning (ML) and deep learning (DL) improve diagnostic accuracy, but they do not autonomously adapt and are pre-trained on complex color variation, whereas traditional computer-based methods lack analysis ability. This review summarizes major pathogens in terms of their types, toxicity, and infection-related mortality, while highlighting research gaps between conventional optical biosensors and emerging AI-assisted colorimetric approaches. Recent advances in AI models, such as ML and DL algorithms, are discussed with a focus on their applications to clinical samples over the past five years. Finally, we propose a prospective direction for developing robust, explainable, and smartphone-compatible AI-assisted assays to support rapid, accurate, and user-friendly pathogen detection for health and clinical applications. This review provides a comprehensive overview of the AI models available to assist physicians and researchers in selecting the most effective method for pathogen detection. Full article
(This article belongs to the Special Issue Colorimetric Sensors: Methods and Applications (2nd Edition))
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