Hue Parameter Research Articles

The temporal changes of pigments content and key enzyme activities during autumnal turning period of Pistacia chinensis bunge

In this study, the temporal regularity of pigments and key enzyme intermediates of Pistacia chinensis Bunge in the color-changing period was investigated to provide a theoretical basis for exploring the mechanism of leaf discoloration. The pigment content and activities of key enzymes of P. chinensis during leaf discoloration were investigated. The correlation between leaf discoloration and environmental factors (temperature, relative humidity, light) was also analyzed. During the color change, the chlorophyll content decreased, while no significant change in the carotenoid content was observed. The anthocyanin content significantly increased in the middle of the period of color change. The ratios of carotenoids/chlorophyll and anthocyanins/chlorophyll showed an upward trend during the period of color change. The lightness parameter (L) and hue parameter (B) of P. chinensis Bunge leaves showed a fluctuating tendency, reaching the highest value at the beginning of color conversion. The hue parameter (A) showed an upward trend at the color conversion stage. The 5-aminolevulinic acid (ALA) and porphobilinogen (PBG) values showed an upward-downward-upward trend. The contents of ALA and PBG at the end of the color transformation were 2.01 times and 2.88 times higher than those at the beginning. The activity of phenylalaninammo-nialyase increased during the color change period. Chalcone isomerase and chalcone synthase first increased, then declined, reaching their highest level in the middle of color conversion, 261.0 u/g and 157.3 u/g, respectively. Although the activities of both enzymes declined at the end of the color conversion, they were higher than at the beginning of the color change. Anthocyanin content was negatively correlated with temperature, relative humidity, day length, and chalcone isomerase, whereas it was positively correlated with phenylalaninammo-nialyase. The results revealed the reasons for the discoloration of P. chinensis leaves in autumn and thus should be considered when exploring the mechanism of color-changing plants and performing color-changing plant applications.

Engineering an Enzymatic Cascade Catalytic Smartphone-Based Sensor for Onsite Visual Ratiometric Fluorescence-Colorimetric Dual-Mode Detection of Methyl Mercaptan.

Precise and reliable onsite detection of methyl mercaptan (CH3SH) is of great significance for environmental surveillance. Here, we synthesized a novel blue fluorescence nanozyme CeO2@TPE with high peroxidase-like activity by employing aggregation-induced emission (AIE) tetraphenylethene (TPE) to embed into hollow CeO2 nanospheres. In the presence of ethanol oxidase (AOX) and o-phenylenediamine (OPD), we engineered an enzymatic cascade activation ratiometric fluorescence-colorimetric dual-mode system AOX/CeO2@TPE + OPD toward CH3SH. In this design, CH3SH initiated AOX catalytic activity to convert it into H2O2 for activating the peroxidase-like activity of CeO2@TPE, producing •OH for oxidizing the naked-eye colorless OPD into deep yellow 2,3-diaminophenazine (DAP) with an absorption enhancement at ∼425 nm, companied by a new emission peak at ∼550 nm to match with the intrinsic emission at ∼441 nm for observing ratiometric fluorescence response, enabling a ratiometric fluorescence-colorimetric dual-mode analysis. Interestingly, both the ratiometric fluorescence and colorimetric signals could be gathered for being converted into the hue parameter on a smartphone-based sensor, achieving the onsite visual fluorescence-colorimetric dual-mode detection of CH3SH in real environmental media with acceptable results. This study gave a novel insight into designing target-responsive enzymatic cascade activation system-based efficient and reliable dual-mode point-of-care sensors for safeguarding environmental health.

Colour Catcher® sheet beyond the laundry: A low-cost support for realizing porphyrin-based mercury ion sensors

The detection of mercury ions in drinkable water is a challenging task, because this heavy metal should be detected in very low concentrations. While analytical laboratory instruments can allow reaching the required sensitivity, the need for continuous monitoring of water samples by chemical sensors is more difficult. In this work, we report the development of a simple colorimetric approach based on the color variation of a free base porphyrin upon interaction with Hg(II) ions. The support is made by Color Catcher® strip embedded by the tetra (4-carboxyphenyl)porphyrin; the anionic character of the porphyrin allows a uniform and stable deposition onto the positively charged solid support. An optical platform, composed of low cost electronic devices, such as LED and webcam, coupled to a PC has been developed to digitalize the images of the strip color changes upon the flux of water solution containing Hg(II) ions. Homemade software developed in Matlab, using the Hue parameter, was exploited to analyze the color changes, allowing reaching a LOD three times below the Hg(II) legal limit stabilized by WHO. The device also showed good selectivity towards other potential interferent metal ions, demonstrating the potentialities of this approach in the real field.

Smartphone-based colorimetric analysis of structural colors from pH-responsive photonic gel

We report a smartphone-based colorimetric analysis of an inverse opal photonic gel (IOPG) sensor that exhibits reversible color changes corresponding to a specific analyte. Herein, pH-responsive IOPG sensors containing a copolymer including poly(acrylic acid) were fabricated by opal-templated photopolymerization. The structural colors of an IOPG sensor templated by a 235 nm-sized microsphere changed from green to red upon increasing the pH, and the colors of a 200 nm microsphere sensor changed from blue to green. Up to now, UV–vis spectrometry has been commonly used for precision analysis to obtain a reflectance spectrum from an IOPG and for a subsequent peak analysis. However, a typical spectrometer comprises benchtop equipment that is bulky, expensive, and often time-consuming to use. Therefore, we investigated a smartphone-based mobile sensing approach as a simple, inexpensive, and rapid alternative to the conventional method by leveraging its built-in functions. In this approach, we use the hue (H) parameter in HSV color space instead of RGB color coordinates which are not directly related to the wavelengths of the visible light spectrum. Through rigorous examinations, the smartphone-based H analysis of the IOPG sensor was found to be applicable with reasonable precision under common illuminations such as fluorescent light, LED, or the built-in flash of a smartphone. Both green-red and blue-green IOPGs showed similar reliability in the colorimetric determination of pH in the range of interest. Results suggest that there was no significant dependence of the colorimetric analysis on smartphones from different companies.

Comparative Assessment of Three Toothpastes and Prophylactic Polishing Paste as A Method of Iron Stain Removal in Primary Teeth: An in-Vitro Study

Aim: To compare and assess the efficacy of three toothpastes compared to prophylactic polishing paste as iron stain removal method in extracted primary teeth. Method: Sixty extracted primary anterior teeth were decoronated at cementoenamel junction, followed by filling the pulp chamber with flowable composite. The teeth were then immersed in ferrous sulphate solution and digital images were obtained. The teeth were subjected to electric tooth brushing using Colgate® Visible White (Group A), Himalaya® Sparkling White (Group B) and Biomed ® Superwhite (Group C) toothpastes. Prophylactic polishing paste (Group D) was used as control for stain removal. Post-intervention digital images were obtained and color parameter differences (L*, a*, b *, hue, chroma and ΔE) were evaluated using image color summarizer software. The data was then statistically analysed using one way ANOVA test. Intergroup analysis was done using bon ferroni multiple comparison test. Results: Significant differences in L* and b* colour parameters were obtained for Group A, B and D (p < 0.05); however, a* parameter did not show a significant change in values for any group. A significant difference was observed in terms of chroma in groups A, C and D. No significant difference was observed in hue parameter values for all four groups. Intergroup comparison of ΔE revealed significant differences between groups D (p < 0.05) and group A, B and C respectively.

Wireless wearable wristband for continuous sweat pH monitoring

Several studies have shown that the determination of pH in sweat, which is one of the most accessible body fluids, can be an indicator of health and wellness, and even be used for potential disease diagnosis. On that basis, we present herein a wearable wristband for continuous and wireless monitoring of sweat pH with potential applications in the field of personal health assessment. The developed wristband consists of two main parts: a microfluidic cloth analytical device (μCAD) to collect continuously the sweat from skin with a color-based pH sensing area; and a readout and processing module with a digital color sensor to obtain the pH of sweat from the color changes in the μCAD. In addition, the readout module includes a low-power Bluetooth interface to transmit the measurements in real-time to a custom-designed smartphone application. To allow continuous operation, an absorbent pad was included in the design to retire and store thsweat from the sensing area through a passive pump path. It was found that the Hue parameter (H) in the HSV color space can be related to the sweat pH and fitted to a Boltzmann equation (R2 = 0.997). The range of use of the wristband device goes from 6 to 8, which includes the pH range of sweat, with a precision at different pH values from 3.6 to 6.0 %. Considering the typical human sweat rate, the absorbent pad allows continuous operation up to more than 1000 min.

Characteristic of Color-Play on Liquid Crystal Sheet Based on Image Analysis

In this research, we compare two samples of Liquid Crystal sheet (LCs), R30C5W and R35C5W to get information about the characteristic of LCs based on the color-play of the LCs surface caused by increasing of temperature. We analize the color-play of the samples quantitatively by image analysis using hue parameter, texture analysis method by choosing entropy and energy parameter, and color-play area measurement. According to the experiment results, both samples show the similar characteristic in color-play behaviour, illustrated by similar curve for each sample, the different only in the starting temperature of the color-play and the clearing point temperature. The samples also show the same behavior in increasing of the color-play area linearly by increasing of temperature. Based on the graph of hue, entropy and energy parameters, it can be measured the clearing-point temperature of samples at 43 °C and 49 °C for LCs R30C5W and LCs R35C5W respectively. Moreover, the changes of color from red to blue cause the irregularity of pattern illustrated by increasing of entropy values and decreasing of energy values. Study the characteristic of LCs in various types is important particularly before it is used for many application purposes, for instance in heat transfer observation.

The Temperature Dependence of Optical Texture in Chiral Nematic Liquid Crystal Observed by Polarizing Microscope

Study the optical-thermal dependence of liquid crystal based on the quantity data of image texture is important to get more information accurately. In this research, the optical-thermal dependence of chiral nematic liquid crystals ink sample was investigated based on the texture and color changes of the sample at various temperatures. The textures of the samples were recorded by the crossed-polarizing optical microscope attached to the hot stage and a camera. The temperature dependence of textures are represented by the hue parameter values taken from the HSV image type. The result obtained from the graph of the increase mean hue parameter against the temperatures was in accordance with the preceding results done by the various techniques. The results show that the higher the temperature of the material, the higher the average hue value. The increase in the hue parameter relates to the color changes of texture from red-dominant to green-dominant. The color difference appeared in various wavelengths represent a diffraction pattern caused by its optically active and the twisted molecular structure. Approaching to the Bragg diffraction equation, the pitch obtained at 0.7 <i>µ</i>m. Furthermore, the relation of the different textures and the twist structure of the sample was evaluated. Considering the sample thickness of 100 µm carries out to the conclusion that there are hundreds of twisted nematic liquid crystal molecules in various alignment on a volume space.

Use of maltodextrin and gum arabic for encapsulation of red cabbage anthocyanins

Maltodextrin (MD) and two types of gum arabic (IRX 40642 and IRX 49345) were used to encapsulate anthocyanins of red cabbage. The solution of the encapsulated dye was evaluated by polarized light microscopy. The spray-dried powder (microspheres) containg anthocyanins (red cabbage juice obtained by disintegration and filtration) and encapsulating agent was characterized by Scanning Electron Microscopy (SEM) and water sorption isotherms; the product color characterization was measured using software of imaging analysis (Mathematica). The microspheres showed that in gum arabic solutions, the dye was located at the wall. Specifically, dried gum arabic microspheres had a better quality than that produced by the maltodextrin because the MD does not form microsphere, but serving only as wall material. GAB isotherm was well fitted on experimental water sorption data. Through the color parameters quantified in CIELab and CIELCH systems for anthocyanin solutions in the presence of three studied encapsulating agents, it was possible to observe that maltodextrin had little effect on the coloring of the dye solution, for example, through the analysis of the hue parameter H, which was least affected by changes in concentration or pH from 5.0 to 3.0. The gum arabic IRX 40642 showed an oxidized hue, while gum arabic IRX 49345 gave similar colors to the original dye at concentrations less or equal to 10%. Even with some limitations, it was concluded that the gums used in this study are suitable for the encapsulation of red cabbage anthocyanins.

Hue- and Chromaticity-Based Exploration of Surface Complexation-Induced Tunable Emission from Non-Luminescent Quantum Dots.

Herein we report the use of a hue parameter of HSV (Hue, Saturation and Value) color space-in combination with chromaticity color coordinates-for exploring the complexation-induced luminescence color changes, ranging from blue to green to yellow to white, from a non-luminescent Fe-doped ZnS quantum dot (QD). Importantly, the surface complexation reaction helped a presynthesized non-luminescent Fe-doped ZnS QD to glow with different luminescence colors (such as blue, cyan, green, greenish-yellow, yellow) by virtue of the formation of various luminescent inorganic complexes (using different external organic ligands), while the simultaneous blue- and yellow-emitting complex formation on the surface of non-luminescent Fe-doped ZnS QD led to the generation of white light emission, with a hue mean value of 85 and a chromaticity of (0.28,0.33). Furthermore, the surface complexation-assisted incorporation of luminescence properties to a non-luminescent QD not only overcomes their restricted luminescence-based applications such as light-emitting, biological and sensing applications but also bring newer avenues towards unravelling the surface chemistry between QDs and inorganic complexes and the advantage of having an inorganic complex with QD for their aforementioned useful applications.

Integrating Target-Responsive Hydrogels with Smartphone for On-Site ppb-Level Quantitation of Organophosphate Pesticides.

Precise on-site profiling of organophosphate pesticides (OPs) is of significant importance for monitoring pollution and estimating poisoning. Herein, we designed a simple and convenient portable kit based on Ag+-responsive hydrogels for accurate detection of OPs. The newly developed hydrogels employed o-phenylenediamine (OPD) and silicon quantum dots (SiQDs) as indicator, which possessed ratiometric response. In this sensor, OPs as inhibitor of acetylcholinesterase prevented the generation of thiocholine, which blocked the formation of metal-polymer with Ag+, further triggered the oxidation of OPD to yield yellow 2,3-diaminophenazine (DAP) with fluorescence emission at 557 nm. The fluorescence intensity of SiQDs (444 nm) was quenched by DAP through inner filter effect (IFE) process, emerging a typical ratiometric response. Interestingly, the ratiometric signal of kit, which was recorded by smartphone's camera, can be transduced by ImageJ software into the hue parameter that was linearly proportional to the concentration of OPs. The simplicity of portable kit combined with smartphone operation, which possessed high sensitivity (detection limit <10 ng mL-1) and rapid sample-to-answer detection time (45 min) in agricultural sample, indicating that the methodology offered a new sight for portable monitoring of food safety and human health.

Protein-Inorganic Hybrid Nanoflower-Rooted Agarose Hydrogel Platform for Point-of-Care Detection of Acetylcholine.

Rapid and precise profiling of acetylcholine (ACh) has become important for diagnosing diseases and safeguarding health care because of its pivotal role in the central nervous system. Herein, we developed a new colorimetric sensor based on protein-inorganic hybrid nanoflowers as artificial peroxidase, comprising a test kit and a smartphone reader, which sensitively quantifies ACh in human serum. In this sensor, ACh indirectly triggered the substrate reaction with the help of a multienzyme system including acetylcholinesterase, choline oxidase, and mimic peroxidase (nanoflowers), accompanying the enhancement of absorbance intensity at 652 nm. Therefore, the multienzyme platform can be used to detect ACh via monitoring the change of the absorbance in a range from 0.0005 to 6.0 mmol L-1. It is worth mentioning that the platform was used to prepare a portable agarose gel-based kit for rapid qualitative monitoring of ACh. Coupling with ImageJ program, the image information of test kits can be transduced into the hue parameter, which provides a directly quantitative tool to identify ACh. Based on the advantages of simple operation, good selectivity, and low cost, the availability of a portable kit for point-of-care testing will achieve the needs of frequent screening and diagnostic tracking.

Battery-Less NFC Sensor for pH Monitoring

In this paper, we present a low-cost battery-less color sensor based on Near Field Communication (NFC). This system consists of a color sensor connected to a low-power microcontroller connected to an NFC chip. The energy needed to power up the chipset is retrieved from the magnetic field generated by the reader, i.e., a commercial smartphone. The low cost of NFC chips affords the opportunity to manufacture low-cost tags with sensing capability. We have developed a mobile application to simultaneously present the data and send them to a database in the cloud. The system has been tested with several pH reactive strips. The pH was determined via color measurement using the HSV color space. A simple linear relationship was found between the Hue parameter and the pH. Comparison with the pH determination via smartphone camera showed that the accuracy was greater when the NFC colorimeter was used.

Hue Parameter Fluorescence Identification of Edible Oils with a Smartphone.

Food fraud can be highly lucrative, and high accuracy authentication of various foodstuffs is becoming essential. Olive oil is one of the most investigated food matrices, due to its high price and low production globally, with recent food fraud examples showing little or no high quality olive oil in the tested oils. Here a simple method using a 405 nm LED flashlight and a smartphone is developed for edible oil authentication. Identification is fingerprinted by intrinsic fluorescent compounds in the oils, such as chlorophylls and polyphenols. This study uses the hue parameter of HSV-colorspace to authenticate 24 different edible oils of 9 different types and 15 different brands. For extra virgin olive oil, all nine samples are well separated from the other oil samples. The rest of the samples were also well type-distinguished by the hue parameter, which is complemented by hue-histogram analysis. This opens up opportunities for low-cost and high-throughput smartphone field-testing of edible oils on all levels of the production and supply chain.

Test strips based on iron(iii)-impregnated alginate/polyacrylonitrile nanofibers for naked eye screening of tetracycline.

Tetracycline (TC) is an inexpensive broad-spectrum antibiotic used to treat infectious diseases and to promote growth in animals. However, driven by economic interest, abuse of TC poses a serious threat to human beings, and it remains a significant challenge to create easy-to-use TC colorimetric test strips for public use. Herein, we present a strategy to prepare free-standing, nanofibrous structured test strips with tortuous porous structure and large surface area by combining polyacrylonitrile nanofibrous membranes (PAN NMs), alginate, and Fe3+. In this approach, alginate was first functionalized on the PAN NMs and then, Fe3+ was assembled into the alginate to construct a TC-sensing surface. The resultant test strips exhibited the following integrated properties: fast sensing process (10 min), low naked eye detection limit (5 μg kg-1), excellent anti-interference ability, and satisfactory reusability. Furthermore, the TC concentration-dependent color change (yellow to maroon) was quantitatively visualized by an iPhone read-out hue parameter. All the findings indicate that this intriguing approach may pave the way for versatile designing of NMs to serve as a preventive treatment for the public.

Highly selective vapochromic fluorescence of polycarbonate films Doped with an ICT‐Based solvatochromic probe

ABSTRACTThe vapochromic properties of a fluorescent 3‐[2‐(4‐nitrophenyl) ethenyl]‐1‐(2‐ethylhexyl)‐2‐methylindole (NPEMI‐E) characterized by intramolecular charge transfer (ICT) character, dispersed in polycarbonate (PC) films is reported. NPEMI‐E solvatochromism is investigated by means of experimental and computational methods. Fluorescent PC films containing 0.1 wt % of NPEMI‐E are prepared and exposed to saturated atmospheres of different volatile organic compounds (VOCs). NPEMI‐E/PC films show remarkable and reversible vapochromism when exposed to VOCs with high polarity index and favorable interaction with PC matrix such as CHCl3. Only minor variations in the emission wavelength are actually recorded for all other classes of VOCs investigated. The hue parameter is also used for the effective extraction of spectral information from digital color images without the need for wavelength discriminators. Overall, the present results support the use of NPEMI‐E/PC films for the cost‐effective detection of CHCl3 vapors. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1171–1180

Hue-based quantification of mechanochromism towards a cost-effective detection of mechanical strain in polymer systems.

HSV is a digital colour space easily accessible by the transformation of RGB images. In this work, the hue parameter H was used to assess mechanically induced colour changes of the aggregation-sensitive fluorescent dye 4,4'-bis-(2-benzoxazolyl)stilbene (BBS), thus implementing a cheap and reliable method for the detection of mechanical deformation in a polymer matrix.

Carbon dots originated from carnation for fluorescent and colorimetric pH sensing

Herein, fluorescent carbon dots (CDs) originated from carnation were creatively synthesized with well-distributed size. By detailed characterization, the prepared CDs were mainly composed of C and O as well as limited amount of N, and there existing O–H, N–H, C–H, C=N, C=O, C=C and C–O groups on their surfaces. Significantly, these CDs showed a distinct pH-sensitive feature. To be specific, the fluorescence intensity of CDs exhibited a linear fashion over the pH range from 11.7 to 3.2. Simultaneously, the color of the CDs solution varied from yellow to yellow–orange, and the corresponding hue parameter decreased linearly with the pH value range from 10.6 to 5. All these evidence illustrated that this CDs have potential as colorimetric and fluorescent sensors for pH sensing. Additionally, The CDs were applied for cellular imaging and painting.

Leaf hue measurements offer a fast, high-throughput initial screening of photosynthesis in leaves

Experiments with tobacco and grapevine leaves having different color due to varying stages of senescence showed that leaf hue is significantly linearly correlated with chlorophyll content up to 80% loss of pigment. Samples from leaves with more pronounced loss of chlorophyll did not fit into this linear relationship, and the hue data set as a whole followed a saturating exponential dependence on chlorophyll content. In leaves with less than 80% chlorophyll loss, the hue parameter was also proportional to the photochemical yield of photosystem (PS) II measured in the light. These results suggest that leaf hue measurements offer a fast, high-throughput initial screening system to precede more specific but more time consuming photosynthesis measurements, with the possibility of applications not only for senescing plants, but also for stress conditions accompanied by chlorophyll loss.

Synergism between lipoxygenase‐active soybean flour and ascorbic acid on rheological and sensory properties of wheat bread

AbstractBACKGROUND: The interaction between lipoxygenase‐active soybean flour (LOX) and ascorbic acid (AA), on colour, rheological and sensory properties of wheat bread was studied with the aim of reducing the applied quantity of additives in bread formulations.RESULTS: The ascorbic acid (0–500 ppm) and active soybean flour (0–1%) mixture improved bread‐crumb colour by lowering the yellow hue in a higher proportion than those expressed by the components alone, characterising a synergistic mechanism (ŷb = 15.1− (1.7 × LOX) − (0.5 × AA) − (5.8 × LOX × AA), where ŷb represent the estimated value for the yellow hue parameter). No differences in flavour and porosity were seen between the samples. As supported by the instrumental methods, breads made with active soybean flour and ascorbic acid (LOX + AA) had whiter crumbs and were softer and springier than controls as assessed by a trained sensory panel. In summary, the combination of both active soybean flour and ascorbic acid showed synergism, promoting a greater bleaching effect than when used alone.CONCLUSION: These results suggest the potential use of active soybean flour as a synergistic ingredient in the substitution of artificial additives in bread making. Since the interaction on the bleaching response was not linear and active soybean flour showed a higher iron concentration (66.40 ± 4.23 µg g−1) than non‐active soybean flour (52.30 ± 0.40 µg g−1), more studies are warranted to establish the biochemical mechanisms involved in this interaction. Copyright © 2007 Society of Chemical Industry