Research

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12 pages, 3519 KiB

Open AccessArticle

A Simple Colorimetric and Fluorescent Sensor to Detect Organophosphate Pesticides Based on Adenosine Triphosphate-Modified Gold Nanoparticles

by Xiaoxia Li, Haixin Cui and Zhanghua Zeng

Sensors 2018, 18(12), 4302; https://doi.org/10.3390/s18124302 - 06 Dec 2018

Cited by 33 | Viewed by 5577

Abstract

A simple and dual modal (colorimetric and fluorescent) sensor for organophosphate pesticides with high sensitivity and selectivity using adenosine triphosphate (ATP)- and rhodamine B-modified gold nanoparticles (RB-AuNPs), was successfully fabricated. This detection for ethoprophos afforded colorimetric and fluorescence imaging changes visualization. The quantitative [...] Read more.

A simple and dual modal (colorimetric and fluorescent) sensor for organophosphate pesticides with high sensitivity and selectivity using adenosine triphosphate (ATP)- and rhodamine B-modified gold nanoparticles (RB-AuNPs), was successfully fabricated. This detection for ethoprophos afforded colorimetric and fluorescence imaging changes visualization. The quantitative determination was linearly proportional to the amounts of ethoprophos in the range of a micromolar scale (4.0–15.0 µM). The limit of detection for ethoprophos was as low as 37.0 nM at 3σ/k. Moreover, the extent application of this simple assay was successfully demonstrated in tap water samples with high reliability and applicability, indicating remarkable application in real samples. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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8 pages, 2249 KiB

Open AccessArticle

Functionalized Silver Nano-Sensor for Colorimetric Detection of Hg²⁺ Ions: Facile Synthesis and Docking Studies

by Kollur Shiva Prasad, Govindaraju Shruthi and Chandan Shivamallu

Sensors 2018, 18(8), 2698; https://doi.org/10.3390/s18082698 - 16 Aug 2018

Cited by 31 | Viewed by 4397

Abstract

In the present study, we describe the facile synthesis of silver nanoparticles (AgNPs) and their nanostructures functionalized with 2-aminopyrimidine-4,6-diol (APD-AgNPs) for Hg²⁺ ion detection. The promising colorimetric response of APD-AgNPs to detect Hg²⁺ ions was visible with naked eyes and spectroscopic [...] Read more.

In the present study, we describe the facile synthesis of silver nanoparticles (AgNPs) and their nanostructures functionalized with 2-aminopyrimidine-4,6-diol (APD-AgNPs) for Hg²⁺ ion detection. The promising colorimetric response of APD-AgNPs to detect Hg²⁺ ions was visible with naked eyes and spectroscopic changes were examined by using a UV-Visible spectrophotometer. The aggregation of APD-AgNPs upon addition of Hg²⁺ ions was due to the chelation effect of the functionalized nanostructures and results in a color change from pale brown to deep yellow color. The probing sensitivity was observed within five minutes with a detection limit of about 0.35 µM/L. The TEM images of APD-AgNPs showed polydispersed morphologies with hexagonal, heptagonal and spherical nanostructures with an average size between 10 to 40 nm. Furthermore, the sensing behavior of APD-AgNPs towards Hg²⁺ ions detection was investigated using docking and interaction studies. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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13 pages, 3641 KiB

Open AccessArticle

A Colorimetric Probe Based on Functionalized Gold Nanorods for Sensitive and Selective Detection of As(III) Ions

by Kun Ge, Jingmin Liu, Guozhen Fang, Peihua Wang, Dongdong Zhang and Shuo Wang

Sensors 2018, 18(7), 2372; https://doi.org/10.3390/s18072372 - 21 Jul 2018

Cited by 16 | Viewed by 4576

Abstract

A colorimetric probe for determination of As(III) ions in aqueous solutions on basis of localized surface plasmon resonance (LSPR) was synthesized. The dithiothreitol molecules with two end thiols covalently combined with Au Nanorods (AuNRs) with an aspect ratio of 2.9 by Au-S bond [...] Read more.

A colorimetric probe for determination of As(III) ions in aqueous solutions on basis of localized surface plasmon resonance (LSPR) was synthesized. The dithiothreitol molecules with two end thiols covalently combined with Au Nanorods (AuNRs) with an aspect ratio of 2.9 by Au-S bond to form dithiothreitol coated Au Nanorods (DTT-AuNRs), acting as colorimetric probe for the determination of As(III) ions. With the adding of As(III) ions, the AuNRs will be aggregated and leading the longitudinal SPR absorption band of DTT-AuNRs decrease due to the As(III) ions can bind with three DTT molecules through an As-S linkage. The potential factors affect the response of DTT-AuNRs to As(III) ions including the concentration of DTT, pH values of DTT-AuNRs, reaction time and NaCl concentration were optimized. Under optimum assay conditions, the DTT-AuNRs colorimetric probe has high sensitivity towards As(III) ions with low detection limit of 38 nM by rules of 3σ/k and excellent linear range of 0.13–10.01 μM. The developed colorimetric probe shows high selectivity for As(III) ions sensing and has applied to determine of As(III) in environmental water samples with quantitative spike-recoveries range from 95.2% to 100.4% with low relative standard deviation of less than 4.4% (n = 3). Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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15 pages, 9345 KiB

Open AccessArticle

Investigation of Gasochromic Rhodium Complexes Towards Their Reactivity to CO and Integration into an Optical Gas Sensor for Fire Gas Detection

by Carolin Pannek, Karina R. Tarantik, Katrin Schmitt and Jürgen Wöllenstein

Sensors 2018, 18(7), 1994; https://doi.org/10.3390/s18071994 - 21 Jun 2018

Cited by 9 | Viewed by 3799

Abstract

The detection of the toxic gas carbon monoxide (CO) in the low ppm range is required in different applications. We present a study of the reactivity of different gasochromic rhodium complexes towards the toxic gas carbon monoxide (CO). Therefore, variations of binuclear rhodium [...] Read more.

The detection of the toxic gas carbon monoxide (CO) in the low ppm range is required in different applications. We present a study of the reactivity of different gasochromic rhodium complexes towards the toxic gas carbon monoxide (CO). Therefore, variations of binuclear rhodium complexes with different ligands were prepared. They were characterized by FTIR spectroscopy, ¹H NMR spectroscopy, and differential scanning calorimetry. All complexes are spectroscopically distinguishable and temperature stable up to at least 187 °C. The gasochromic behavior of all different compounds was tested. Therefore, the compounds were dissolved in toluene and exposed to 100 ppm CO for 10 min to investigate their gas sensitivity and reaction velocity. The changes in the transmission spectra were recorded by UV/vis spectroscopy. Furthermore, a significant influence of the solvent to the color dyes’ gasochromic reaction and behavior was observed. After characterization, one complex was transferred as sensing element into an optical gas sensor. Two different measurement principles (reflection- and waveguide-based) were built up and tested towards their capability as gasochromic CO sensors. Finally, different gas-dependent measurements were carried out. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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6 pages, 907 KiB

Open AccessArticle

Improving Color Accuracy of Colorimetric Sensors

by Eric Kirchner, Pim Koeckhoven and Keshav Sivakumar

Sensors 2018, 18(4), 1252; https://doi.org/10.3390/s18041252 - 18 Apr 2018

Cited by 8 | Viewed by 6213

Abstract

Accurate measurements of reflectance and color require spectrophotometers with prices often exceeding $3000. Recently, new “color instruments” became available with much lower prices, thanks to the availability of inexpensive colorimetric sensors. We investigated the Node+ChromaPro and the Color Muse, launched in 2015 and [...] Read more.

Accurate measurements of reflectance and color require spectrophotometers with prices often exceeding $3000. Recently, new “color instruments” became available with much lower prices, thanks to the availability of inexpensive colorimetric sensors. We investigated the Node+ChromaPro and the Color Muse, launched in 2015 and 2016 by Variable Inc. Both instruments are colorimeters, combining a colorimetric sensor with LED lighting. We investigated color accuracy compared to a high-end spectrophotometer from BYK Gardner. With different sets of samples we find for the Node an average value of dE_CMC (1:1) = 1.50, and a maximum of 7.86, when comparing with the 45° geometry of the spectrophotometer. Utilizing measurement data on the Spectral Power Distributions of the LEDs, we developed three methods to improve color accuracy as compared to the spectrophotometer data. We used these methods on different sets of samples with various degrees of gloss, both for training the models underlying the methods and for independent tests of model accuracy. Average color accuracy of the Node+ChromaPro improves from dE_CMC (1:1) = 1.82 to 1.16 with respect to spectrophotometer data. The percentage of samples with dE_CMC (1:1) < 1.0 increases from 30.9% (uncorrected) to 64%. With the improved color accuracy, these sensors become useful for many more applications. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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14 pages, 4029 KiB

Open AccessArticle

A Miniaturized Colorimeter with a Novel Design and High Precision for Photometric Detection

by Jun-Chao Yan, Yan Chen, Yu Pang, Jan Slavik, Yun-Fei Zhao, Xiao-Ming Wu, Yi Yang, Si-Fan Yang and Tian-Ling Ren

Sensors 2018, 18(3), 818; https://doi.org/10.3390/s18030818 - 08 Mar 2018

Cited by 11 | Viewed by 6193

Abstract

Water quality detection plays an increasingly important role in environmental protection. In this work, a novel colorimeter based on the Beer-Lambert law was designed for chemical element detection in water with high precision and miniaturized structure. As an example, the colorimeter can detect [...] Read more.

Water quality detection plays an increasingly important role in environmental protection. In this work, a novel colorimeter based on the Beer-Lambert law was designed for chemical element detection in water with high precision and miniaturized structure. As an example, the colorimeter can detect phosphorus, which was accomplished in this article to evaluate the performance. Simultaneously, a modified algorithm was applied to extend the linear measurable range. The colorimeter encompassed a near infrared laser source, a microflow cell based on microfluidic technology and a light-sensitive detector, then Micro-Electro-Mechanical System (MEMS) processing technology was used to form a stable integrated structure. Experiments were performed based on the ammonium molybdate spectrophotometric method, including the preparation of phosphorus standard solution, reducing agent, chromogenic agent and color reaction. The device can obtain a wide linear response range (0.05 mg/L up to 7.60 mg/L), a wide reliable measuring range up to 10.16 mg/L after using a novel algorithm, and a low limit of detection (0.02 mg/L). The size of flow cell in this design is 18 mm × 2.0 mm × 800 μm, obtaining a low reagent consumption of 0.004 mg ascorbic acid and 0.011 mg ammonium molybdate per determination. Achieving these advantages of miniaturized volume, high precision and low cost, the design can also be used in automated in situ detection. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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Review

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23 pages, 3239 KiB

Open AccessReview

Overview of the Evolution of Silica-Based Chromo-Fluorogenic Nanosensors

by Luis Pla, Beatriz Lozano-Torres, Ramón Martínez-Máñez, Félix Sancenón and Jose V. Ros-Lis

Sensors 2019, 19(23), 5138; https://doi.org/10.3390/s19235138 - 23 Nov 2019

Cited by 11 | Viewed by 3267

Abstract

This review includes examples of silica-based, chromo-fluorogenic nanosensors with the aim of illustrating the evolution of the discipline in recent decades through relevant research developed in our group. Examples have been grouped according to the sensing strategies. A clear evolution from simply functionalized [...] Read more.

This review includes examples of silica-based, chromo-fluorogenic nanosensors with the aim of illustrating the evolution of the discipline in recent decades through relevant research developed in our group. Examples have been grouped according to the sensing strategies. A clear evolution from simply functionalized materials to new protocols involving molecular gates and the use of highly selective biomolecules such as antibodies and oligonucleotides is reported. Some final examples related to the evolution of chromogenic arrays and the possible use of nanoparticles to communicate with other nanoparticles or cells are also included. A total of 64 articles have been summarized, highlighting different sensing mechanisms. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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35 pages, 2270 KiB

Open AccessReview

Novel Spectroscopic and Electrochemical Sensors and Nanoprobes for the Characterization of Food and Biological Antioxidants

by Reşat Apak, Sema Demirci Çekiç, Ayşem Üzer, Saliha Esin Çelik, Mustafa Bener, Burcu Bekdeşer, Ziya Can, Şener Sağlam, Ayşe Nur Önem and Erol Erçağ

Sensors 2018, 18(1), 186; https://doi.org/10.3390/s18010186 - 11 Jan 2018

Cited by 22 | Viewed by 6194

Abstract

Since an unbalanced excess of reactive oxygen/nitrogen species (ROS/RNS) causes various diseases, determination of antioxidants that can counter oxidative stress is important in food and biological analyses. Optical/electrochemical nanosensors have attracted attention in antioxidant activity (AOA) assessment because of their increased sensitivity and [...] Read more.

Since an unbalanced excess of reactive oxygen/nitrogen species (ROS/RNS) causes various diseases, determination of antioxidants that can counter oxidative stress is important in food and biological analyses. Optical/electrochemical nanosensors have attracted attention in antioxidant activity (AOA) assessment because of their increased sensitivity and selectivity. Optical sensors offer advantages such as low cost, flexibility, remote control, speed, miniaturization and on-site/in situ analysis. Electrochemical sensors using noble metal nanoparticles on modified electrodes better catalyze bioelectrochemical reactions. We summarize the design principles of colorimetric sensors and nanoprobes for food antioxidants (including electron-transfer based and ROS/RNS scavenging assays) and important milestones contributed by our laboratory. We present novel sensors and nanoprobes together with their mechanisms and analytical performances. Our colorimetric sensors for AOA measurement made use of cupric-neocuproine and ferric-phenanthroline complexes immobilized on a Nafion membrane. We recently designed an optical oxidant/antioxidant sensor using N,N-dimethyl-p-phenylene diamine (DMPD) as probe, from which ROS produced colored DMPD-quinone cationic radicals electrostatically retained on a Nafion membrane. The attenuation of initial color by antioxidants enabled indirect AOA estimation. The surface plasmon resonance absorption of silver nanoparticles as a result of enlargement of citrate-reduced seed particles by antioxidant addition enabled a linear response of AOA. We determined biothiols with Ellman reagent−derivatized gold nanoparticles. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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