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Peroxides in edible oils, whose amounts are measured using the peroxide value, are closely related to human health. Long-term consumption of edible oils with high peroxide values can lead to a variety of human diseases, which highlights the significance of examining oil types and their corresponding peroxide values. For identifying a wide range of edible oils, we established a colorimetric sensor array based on the halogen ion exchange between CsPbBr3 and two iodides (octadecylammonium iodide (ODAI) and ZnI2). Different kinds of edible oils contain distinct peroxidic substances that have the distinct ability to oxidize iodides. After specific types of edible oils react with excess iodides (ODAI and ZnI2), different amounts of residual iodides are left for further halogen exchange with CsPbBr3, resulting in various colorimetric responses, measured in RGB (red/green/blue) values, under fluorescent light. Based on RGB pattern analysis as fingerprints using two anion exchangers (ODAI and ZnI2), our proposed colorimetric sensor array was proved by linear discriminant analysis (LDA) to have an ability to accurately distinguish edible oils at a minimal volumetric concentration of 6.67% in seven real samples. [ABSTRACT FROM AUTHOR]

Here, we report a simple but effective nose/tongue-mimic sensor array based on HAuCl4/3,3′,5,5′-tetramethylbenzidine (TMB) for colorimetric discrimination and determination of antioxidants. Two concentrations of HAuCl4 were employed as receptor units to construct the colorimetric sensor array. The sensing strategy is based on the fact that HAuCl4 with different concentrations (0.08 and 0.03 mM) could oxidize TMB to oxidized TMB (oxTMB), resulting in a blue and green color solution, respectively, corresponding to an absorption peak centered at 440 nm and 657 nm. However, the presence of different antioxidants could cause the reduction in HAuCl4, leading to the fading of the blue and green color and the decrease in the absorbance at 440 nm and 657 nm to varying degrees. Based on the above phenomena, by taking advantage of linear discriminant analysis (LDA), five antioxidants (i.e. ascorbic acid (AA), melatonin (MT), uric acid (UA), tannic acid (TCA), and glycine (Gly)) at five concentrations (200, 120, 60, 20, and 1 nM) were successfully discriminated both in buffer and serum. More importantly, this approach is simple, fast, and without the use of any nanomaterials. [ABSTRACT FROM AUTHOR]

We report a colorimetric array, which consists of two carboxylic acids (quinolinic acid (QA), tannic acid (TCA)) as the sensor element and Eriochrome Black T (EBT) as the colorimetric signal readout. The assay is based on coordination binding between lanthanide ions and EBT, and between lanthanide ions and the carboxylic acids. The competitive binding of lanthanide ions with the carboxylic acids and EBT leads to the change in absorbance and color of the solutions. To test the efficacy of our sensor array, the sensor array was exposed to five target lanthanide ions (La3+, Sm3+, Eu3+, Gd3+ and Yb3+) with diverse concentrations (10, 50, 100, 200, 300, 400, and 500 nM). Linear discriminant analysis (LDA) results show that the sensor array can identify the five lanthanide ions, with a low discrimination limit of 10 nM. More importantly, the sensor array realizes fast discrimination of lanthanide ions in river samples, showing potential in environmental monitoring. [ABSTRACT FROM AUTHOR]

There is growing interest in developing a high-performance sensor array for detection and discrimination of antioxidants owing to their widespread use and essential role in the human body. The present work unveils a novel colorimetric sensor array for colorimetric discrimination of antioxidants based on the red, green, and blue alteration (ΔRGB) pattern recognition. In this sensor array, three concentrations of AgNO3 were used as sensing elements, and gold nanoparticles (AuNPs) were employed as a colorimetric probe. In the presence of antioxidants, the sensor array produces unique colorimetric response patterns for the discrimination of these antioxidants due to different reactivities between three different concentrations of AgNO3 and each antioxidant, leading to deposition of different quantities of Ag nanoshells on the surface of AuNPs, enabling an excellent discrimination of six antioxidants (catechin, epigallocatechin 3-gallate, epicatechin, epigallocatechin, epicatechin 3-gallate, and gallocatechin) at a 20 nM level, when linear discriminant analysis (LDA), hierarchical cluster analysis (HCA), centroid diagram, spidergram, and color contour profiles were smartly combined. Furthermore, different concentrations of antioxidants and binary antioxidant mixtures, even ternary mixtures, could also be discriminated with this sensor array. Finally, the sensor array was successfully used for the discrimination of antioxidants in serum samples, demonstrating its potential applications in the diagnosis of antioxidant-related diseases. [ABSTRACT FROM AUTHOR]

Proteins play a key role in disease diagnosis, and protein discrimination is an important but difficult issue. Here, we report a novel strategy for improving protein discrimination through a facile colorimetric sensor array, which is based on DNA–gold nanoparticle (AuNP) conjugates manipulated by exonuclease I (Exo I). Different proteins exhibit diverse affinities toward the three DNAs, and the DNA–protein binding is resistant to the digestion of Exo I and protects the AuNPs from aggregation in high concentrations of NaCl media, forming distinct response patterns of the array. These response patterns as “fingerprints” can be acquired on the sensor array and then identified by linear discriminant analysis (LDA). The sensor array achieved the correct discrimination of 15 proteins at a 10 nM level in buffer solution and real serum samples. Also, the sensor array had the capability to discriminate individual proteins and the mixtures of them. Remarkably, the practicability of the sensor array was further confirmed by the identification of 35 unknown protein samples with 100% accuracy. [ABSTRACT FROM AUTHOR]

We herein present a simple, low-cost, and ultrasensitive colorimetric sensing strategy for the detection of mercury ions (Hg2+) that takes advantage of the natural pore structure in rose petals to encapsulate gold nanoparticles (AuNPs). AuNPs easily aggregate in high salt concentrations, which restrict their application, for example, as a catalyst in real sample analysis. Rose petals offer a three-dimensional (3D) space for more efficient dispersability of AuNPs in their extensive network of channels, which will increase the specific surface area, thereby enhancing the catalytic capability of AuNPs. The presence of Hg2+ triggers the formation of gold amalgam, which results in remarkable enhancement of the catalytic ability of citrate-capped AuNPs. On the basis of this effect, a colorimetric signal amplification is achieved via the use of gold amalgam to catalyze the reaction of methylene blue (MB) and sodium borohydride. A limit of detection (LOD) as low as 10 fM can be obtained by naked eye observation. Our sensor has promising potential for detection and quantitation of Hg2+ in environmental samples. [ABSTRACT FROM AUTHOR]

Breaking the restrictions of a lock-and-key sensing strategy which relies only on the most dominant interactions between the sensing element and target, here, we develop a colorimetric sensor array with three kinds of cationic polymers (polydiallyl dimethylammonium chloride (PDDA), chitosan (CTS), and cetyltrimethylammonium bromide (CTAB)) as nonspecific receptors. Diverse interactions between cationic polymers and proteins make gold nanoparticles (Au NPs) exhibit different aggregation behaviors, resulting in changes in color and absorbance of Au NPs. Based on the diverse colorimetric response patterns, seven proteins were successfully discriminated visually at the 20 nM level by linear discrimination analysis (LDA). Furthermore, the practicability of the sensor array was validated by the successful identification of proteins without any overlap in human serum samples. [ABSTRACT FROM AUTHOR]

We present an ultrasensitive colorimetric nucleic acid assay based on the intensity of gold nanoparticles (Au NPs) using dark field microscopy. In the absence of target DNA, two hairpin-like DNA strands with protruding single-stranded DNA (ssDNA) can be absorbed onto the Au NP surface via non-covalent interactions between the exposed nitrogen bases of ssDNA and Au NPs, which inhibits Au NPs from aggregating in a high concentration of salt media, while in the presence of target DNA, two hairpin DNA strands hybridize with target DNA to form double-stranded DNA (dsDNA). After hybridization chain reaction (HCR) amplification, rigid dsDNA polymers are formed, which results in serious Au NP aggregation in the salt environment. By measuring the intensity change of yellow and red dots on a dark-field image, the concentration of target DNA can be accurately quantified with a limit of detection (LOD) of 66 fM. [ABSTRACT FROM AUTHOR]

Peroxides in edible oils, whose amounts are measured using the peroxide value, are closely related to human health. Long-term consumption of edible oils with high peroxide values can lead to a variety of human diseases, which highlights the significance of examining oil types and their corresponding peroxide values. For identifying a wide range of edible oils, we established a colorimetric sensor array based on the halogen ion exchange between CsPbBr 3 and two iodides (octadecylammonium iodide (ODAI) and ZnI 2 ). Different kinds of edible oils contain distinct peroxidic substances that have the distinct ability to oxidize iodides. After specific types of edible oils react with excess iodides (ODAI and ZnI 2 ), different amounts of residual iodides are left for further halogen exchange with CsPbBr 3 , resulting in various colorimetric responses, measured in RGB (red/green/blue) values, under fluorescent light. Based on RGB pattern analysis as fingerprints using two anion exchangers (ODAI and ZnI 2 ), our proposed colorimetric sensor array was proved by linear discriminant analysis (LDA) to have an ability to accurately distinguish edible oils at a minimal volumetric concentration of 6.67% in seven real samples.

Here, we report a simple but effective nose/tongue-mimic sensor array based on HAuCl 4 /3,3',5,5'-tetramethylbenzidine (TMB) for colorimetric discrimination and determination of antioxidants. Two concentrations of HAuCl 4 were employed as receptor units to construct the colorimetric sensor array. The sensing strategy is based on the fact that HAuCl 4 with different concentrations (0.08 and 0.03 mM) could oxidize TMB to oxidized TMB (oxTMB), resulting in a blue and green color solution, respectively, corresponding to an absorption peak centered at 440 nm and 657 nm. However, the presence of different antioxidants could cause the reduction in HAuCl 4 , leading to the fading of the blue and green color and the decrease in the absorbance at 440 nm and 657 nm to varying degrees. Based on the above phenomena, by taking advantage of linear discriminant analysis (LDA), five antioxidants (i.e. ascorbic acid (AA), melatonin (MT), uric acid (UA), tannic acid (TCA), and glycine (Gly)) at five concentrations (200, 120, 60, 20, and 1 nM) were successfully discriminated both in buffer and serum. More importantly, this approach is simple, fast, and without the use of any nanomaterials.

We herein present a simple, low-cost, and ultrasensitive colorimetric sensing strategy for the detection of mercury ions (Hg2+) that takes advantage of the natural pore structure in rose petals to encapsulate gold nanoparticles (AuNPs). AuNPs easily aggregate in high salt concentrations, which restrict their application, for example, as a catalyst in real sample analysis. Rose petals offer a three-dimensional (3D) space for more efficient dispersability of AuNPs in their extensive network of channels, which will increase the specific surface area, thereby enhancing the catalytic capability of AuNPs. The presence of Hg2+ triggers the formation of gold amalgam, which results in remarkable enhancement of the catalytic ability of citrate-capped AuNPs. On the basis of this effect, a colorimetric signal amplification is achieved via the use of gold amalgam to catalyze the reaction of methylene blue (MB) and sodium borohydride. A limit of detection (LOD) as low as 10 fM can be obtained by naked eye observation. Our sensor has promising potential for detection and quantitation of Hg2+ in environmental samples.