Color Change Of Solution Research Articles

Bi-enzyme assay coupled with silver nanoplate transformation for insecticide detection.

A novel colorimetric method utilizing a bi-enzyme assay using silver nanoplates (AgNPls) as a direct signal source was developed to enable rapid insecticide detection. This innovative system leverages the in situ generated H2O2 from the consecutive enzyme-catalyzed reactions of acetylcholine hydrolysis and choline oxidation to introduce oxidative etching of AgNPls, transforming them into aggregated silver nanospheres (AgNSs). The morphological transformation of silver nanoparticles could be observed with the naked eye due to the solution's color shifts from pink-violet to blue-violet. The presence of insecticide, i.e., dichlorvos (DDVP), could inhibit acetylcholinesterase activity, thereby limiting H2O2 production and affecting the transformation of AgNPls into aggregated AgNSs. Furthermore, the extent of AgNPl-to-aggregated AgNS transformation and the subsequent solution's color change was inversely proportional to the amount of DDVP. Under optimal conditions, the developed bi-enzyme assay enables the quantification of DDVP within 5 minutes, achieving detection limits of 0.5 ppm and 0.1 ppm by naked-eye detection and UV-visible spectrophotometry, respectively. Furthermore, the practical application of this assay was validated for detecting insecticides in real vegetable samples, demonstrating both accuracy and reliability.

Turn-on fluorescent probe based on dicyanoisophorone for bioimaging and rapid detection of peroxynitrite in aqueous media.

A novel dicyanoisophorone-based colorimetric fluorescent probe 3 has been prepared for recognizing peroxynitrite in aqueous conditions. A large bathochromic shift of the absorption band is observed upon titration with ONOO-, inducing a clearly visible solution color change from yellow to pale pink, which makes "naked-eye" detection possible. Moreover, probe 3 can react instantly with ONOO- and is accompanied by a significant fluorescence enhancement at 621 nm while the detection limit is as low as 37 nM. Most importantly, probe 3 exhibits high selectivity and sensitivity towards ONOO- in the presence of other competitive ions in aqueous solution. Probe 3 has also been successfully applied in living MCF-7 cells, and the results suggest that probe 3 could be applied as a potential candidate for the detection of ONOO-.

Flexible metallosalen complex for pyrophosphate sensing in biological milieu: Use disassembly strategy for signal amplification

In the present work, we have designed and synthesized two dimeric fluorescein derivatives with flexible salen (1) or a rigid salophen (2) linker unit. The Fe(III) complexes of these compounds ([1.Fe]+ and [2.Fe]+) showed changes in solution color specifically upon addition of inorganic pyrophosphate (PPi) at pH 7.0 in PBS buffer. Along this, we also observe appearance of green fluorescence (turn-on) in the prescence of PPi. The mechanistic studies suggested PPi-induced demetallation process, which led to disassembly for molecular structure in the aqueous medium and release of highly fluorescent fluorescein aldehyde. The disassembly process was found to be dependent on electronic structure, rigidity of the linker unit, temperature, and local pH etc. The selectivity as well as sensitivity of [1.Fe]+ towards PPi was also found to be superior than that observed with [2.Fe]+. Since each disassembly process released two signalling unit (fluorescein), we could observe a huge increment in FL intensity even with small quantity of PPi (<10 µM). Finally, the sensory system was utilized for detection of PPi in diluted blood serum samples and inside living mammalian cells (HeLa, cervical cancer cells). Chemically-modified paper strips have been developed for the detection of PPi in water samples at outside laboratory conditions.

Analysis of Practical Design for Making Natural Acid-Base Indicator Paper from Purple Golden Flower Extract (Ruellia simplex) as Teaching Material for Acid-Base Material

Experiments are an essential part of chemistry. An indicator in the form of a synthetic indicator is generally used in acid-base practice. Using synthetic indicators can cause waste that is dangerous for the environment and is relatively expensive. Purple golden flowers are one of the plants that contain high levels of anthocyanin compounds, which have the potential to be an alternative in making natural acid-base indicators. This research aims to determine the curriculum and learning outcomes of acid-base material, the potential of natural indicator paper for purple golden flowers as a substitute for synthetic indicators, and the feasibility of indicator paper as a design for chemical experiments in SMA/MA. This research uses descriptive qualitative methods, which include literature studies, interviews, observations, and experiments. The purple golden flower indicator is produced by extraction using the maceration method using 96% ethanol solvent. The research results show that paper from purple golden flower extract can be used as a natural acid-base indicator by producing a pink color change in acidic solutions and a green color in essential solutions. Based on the natural indicator paper analysis, the purple golden flower can be used as an alternative indicator in practicum design in schools

Detection of Heavy Metal Ions Based on Gold Nanoparticles

Gold nanoparticles, abbreviated as AuNPs, have been widely used in catalysis, optics, electronics, and biotechnology due to their unique performance brought by large specific surface area. In recent years, with the improvement of health awareness, the use of gold nanoparticles to detect heavy metal ions has become a research hotspot. The detection is based on colorimetric techniques, which means the metal ions are detected through the color change in solutions. This color change is visible or could be distinguished by ultraviolet-vissible spectrometers. Numerous studies have been published on gold nanoparticles, especially for its synthesis methods. This work introduced the chemical, physical, and biological preparation methods of gold nanoparticles. Understanding mechanisms for detecting heavy metal ions using AuNPs is also very important. Aggregating mechanism, anti-aggregation mechanism, and etching mechanism were also introduced. In addition, applications of using AuNPs to detect heavy metal ions were also introduced. This work will help promote the further development of this technology.

Synthesis And Characterisation of Copper Nanoparticles Using Aqueous Leaf Extract of Lagerstreomia Speciose and Their Biological, Antioxidant and catalytic activities

Nanotechnology is gaining importance at tremendous rate in every field of science and technology. Researchers have developed a large number of different methods for the synthesis of nanoparticles; among this green route method is of great importance as it is eco-friendly and cost-effective. In this study we synthesized copper nanoparticles through green synthesis using a plant called lagerstroemia speciose. The formation of copper nanoparticles has been observed due to change in colour of extract solution. The sample solution was characterized by different techniques in order to find out the various physiological parameters like shape, size and nature of bonding. Plant extract acts as both reducing and capping agent .The various instruments used for characterization are DLS (Dynamic Light Scattering), SEM (Scanning Electron Microscopy), X-ray Diffractometry (XRD) and Fourier Transform-Infrared (FT-IR). Cups obtained were of size 35nm. The synthesized copper nanoparticles were studied for their anti-microbial activity, antioxidant, antidiabetic and catalytic activities and cytotoxicity.

Label-free multimodal analysis of copper ions at below permissible exposure limit in the aqueous medium

An anthraimidazoledione based amphiphilic dye molecule was synthesized that shows formation of tuneable charge-transfer state in solution, susceptible to change in pH, polarity and hydrogen bonding ability of the medium. The compound also showed formation of nanoscopic self-assembled structure in water medium. The probe molecule can achieve multimodal detection (colorimetric, fluorimetric and electrochemical) of copper ions as low as 0.3 ppm in the aqueous medium. Addition of copper leads to dose-dependent ratiometric change in solution color from yellow to purple. The mechanistic investigation indicates that the coordination of copper ions was possible via simultaneous engagement of both imidazole nitrogen ends and neighbouring hydroxyl unit. Not only optical property, the changes in microenvironment also influence the selectivity as well as sensitivity of the probe molecule towards Cu2+ ions. Further, the optical probe is used for detection as well as quantification of copper ions in natural water samples without any sample pretreatment. Low-cost, reusable paper strips are developed for rapid, on-location detection of residual Cu2+ in real-life samples.

Water soluble spiropyran for Hg2+ sensing in water

A novel spiropyran derivative was synthesized for heavy metals sensing in water. Considering the environmental and human risks of contamination of heavy metals, it is necessary to develop rapid, sensitive, and simple methods to estimate their presence in water. While spiropyran derivatives have been extensively studied, many are soluble solely in organic solvents. To address this challenge, a spiropyran derivative (SPSO) was synthesized adding the methoxy functional group at the benzopyran moiety and tested for sensing several ions (cations and anions) in aqueous solution. The new derivative was structurally characterized by Fourier transformed infrared (FTIR-ATR), nuclear magnetic resonance (NMR) and single crystal by X-ray diffraction. The SPSO binding affinity to several ions was investigated by spectroscopy measurements (UV–visible absorption analysis and naked eye aqueous solution color change). The results demonstrated a specific colorimetric change of color of the solution when in presence of mercury (II) ion due to the SPSO greater binding affinity. Even though Al3+ and Cu2+ caused a minor decrease in the visible band associated with the MC isomer, only Hg2+ was capable of inducing a shift in the color of the solutions from pink to yellow, even at lower concentrations. The experimental results suggest that SPSO could serve as a rapid, sensitive, and simple tool for detecting Hg2+ ions in water with high selectivity with a LOD of 0.1 mmol.L–1, while maintaining its performance in the presence of potential interferences. Further experiments may still be conducted to evaluate this behavior in samples obtained from contaminated natural sources.

Detection of homogentisic acid by electrospray ionization mass spectrometry.

Homogentisic acid (HGA) is excreted in excessive amounts in the urine of patients with alkaptonuria, which is a hereditary metabolic disorder of phenylalanine and tyrosine. Therefore, the detection of HGA in urine is useful for the diagnosis of alkaptonuria. To evaluate the detection of HGA, we confirmed the color shift of HGA solutions and analyzed them by electrospray ionization mass spectrometry (ESI-MS). We observed the color change of the HGA solutions under different pH conditions (pH 6.0, 7.0, and 8.0) and examined the influences of adding potassium hydroxide (KOH) and ascorbic acid (AA) to the HGA solutions. Then, we analyzed the chemical reaction in HGA solutions using ESI-MS. The HGA solution at pH 8.0 became brown after incubation at room temperature for 24 h and became darker brown with the addition of KOH; however, HGA solutions at pH 6.0 and 7.0 showed no color changes. The brown color change of the HGA solution at pH 8.0 was also inhibited by AA. Moreover, all HGA sample solutions showed the deprotonated molecular ion peak at m/z 167.035 in the negative ion mode after incubation at room temperature for 24 h and with the addition of KOH and AA. We identified the molecular ion of HGA in all sample solutions by ESI-MS, regardless of different pH conditions, color changes, or the presence of AA. These results suggest that spectral analysis by ESI-MS is suitable for the detection of HGA and the diagnosis of alkaptonuria.

Fluorescence Naphthalene Cationic Schiff Base Reusable Paper as a Sensitive and Selective for Heavy Metals Cations Sensor: RSM, Optimization, and DFT Modelling.

Heavy metals are particularly damaging contaminants in the environment, and even trace concentrations represent a risk to human health due to their toxicity. To detect the heavy metals of Mn2+ and Co2+ ions, a novel selective reusable paper-based Fluorescence naked-eye sensor based on naphthalene cationic Schiff base (NCSB) was synthesized and confirmed using FT-IR, 1H-NMR, and MS tools. Based on a blue to colorless color change in the aqueous solution, the NCSB sensor is utilized to Mn2+ and Co2+ cations selectively among other metal ions (Fe2+, Cu2+, Mg2+, Ni2+, Zn2+, Cd2+, Hg2+, Pb2+, Sn2+ and Cr3+). In the aqueous medium, the NCSB sensor displayed high sensitivity, with limits of detection (LOD) values of 0.014 µM (14.08 nM) and 0.041 µM (41.47 nM) for Mn2+ and Co2+ cations, respectively. The paper-based sensor naked-eye detected Mn2+ and Co2+ cations in water at concentrations as low as 0.65 µM (65 nM) and 0.086 µM (86 nM), respectively. It was discovered that 5min of incubation time and a pH range of 7 to 11 were optimal for the complexation reaction between the Mn2+ and Co2+ ions and the NCSB sensor. Through a static quenching process, the interaction of the different metal ions with the Schiff base group in the NCSB molecule results in the development of a ground-state non-fluorescent complex. NCSB sensor was also successfully applied in analysis of Mn2+ and Co2+ in environmental water with good recoveries of 94.8-105.9%. The theoretical calculations based on density functional theory (DFT) studies are in support of experimental interpretations. The links between the input factors and the anticipated response were evaluated using the quadratic model of the response surface methodology (RSM) modeling.

Multimodal Sensing of Acetate Anion by Using Anthraimidazoledione‐Based Redox‐Active Amphiphilic Dye in Aqueous Environment

AbstractAnthraimidazoledione based amphiphilic dye is synthesized that exhibits pH‐responsive chromogenic response in aqueous environment. This entices us to investigate its anion‐responsive behavior. In pure water, the compound shows no optical response towards anions (poor sensitivity), whereas interaction with multiple anions is witnessed in acetonitrile medium (poor selectivity). Interestingly, changes in solution color from yellow to orange is observed explicitly upon addition of acetate anion, accompanied by fluorescence turn‐off response. Further, it is revealed that the acetate engaged in hydrogen bonding interaction with both imidazole −NH group and hydroxyl unit. The high basicity of acetate anion along with ‘Y‐shaped’ structure might be responsible for such unique selectivity. The present system has been involved in analyzing residual acetate in natural water samples. Low‐cost, reusable paper strips have been designed for equipment free, rapid on‐location detection of acetate.

Strengthening of reinforced concrete structures by composite materials taking into consideration the carbonization of concrete

One of the main causes for deterioration of reinforced concrete structures in modern construction is corrosion of reinforcement. Corrosion leads to decrease of adhesion between reinforcement and concrete, formation of cracks and destruction of the protective layer of concrete. All this reduces the load-bearing capacity of reinforced concrete structures. The structures of sludge reservoirs exposed to carbon dioxide were used as an object of the study. The characteristic defects and damages revealed by visual inspection were described. The verification calculation of the considered construction depending on the pH of the medium was performed on the basis of the results of technical inspection and study. The degree of carbon dioxide impact on the considered structures was determined by the phenolphthalein test method, which is based on the color change of acid-base indicator solution on the surface of concrete and reinforced concrete depending on the pH value of its medium. The phenolphthalein test revealed that pH of the medium is less than 8 for the depth more than the thickness of the concrete protective layer. A verification calculation of the considered structure was performed on the basis of the technical inspection results and the conducted research. According to the calculation results, a variant of beam reconstruction and strengthening using external reinforcement based on carbon fibers FibARM 230/150 was proposed. The reconstruction was carried out with account of the carbonized concrete layer.

Synthesis and application of purine-based fluorescence probe for continuous recognition of Cu2+ and glyphosate

In this study, a novel fluorescent sensor, N,N-dimethyl-4-((2-(8-m-ethyl-9-(naphthalen-1-yl)-9H-purin-6-yl)hydrazineylidene)methyl)aniline(PHA), which was constructed via Schiff base reaction of purine derivatives and dimethylaminobenzaldehyde. This probe showed significant selective fluorescence quenching of Cu2+, and accompanying with an increase in Cu2+ concentration and a change in solution color from colorless to yellow. The outstanding features of PHA include low detection limit (0.429 μM), strong anti-interference ability and fast response time. We further investigated the chelation mechanism of PHA and Cu2+ by Job's plot experiment, density generalization theory (DFT), and the probe PHA can form a 1:2 complex with Cu2+ ions, leading to a fluorescence quenching process, thus realizing the rapid detection of Cu2+. In addition, this new fluorescent sensor [PHA-Cu2+] can be used to detect pesticide residues in solution. When the [PHA-Cu2+] system was mixed with glyphosate solution, that a fluorescence recovering was observed. This may be because glyphosate chelates more strongly with Cu2+ ions, making the copper ions dissociated from the [PHA-Cu2+] system. The detection limit of the fluorescent sensor [PHA-Cu2+] for glyphosate was 18.77 nM. Finally, the sensor system has been successfully applied in fluorescence imaging of glyphosate in living cells.

Characterizing the Size Distribution of Silver Nanoparticles Biofabricated Using Calotropis gigantea from Geothermal Zone

This research aims to synthesize silver nanoparticles (AgNPs) using an aqueous leaf extract of Calotropis gigantea obtained from the geothermal manifestation Ie Seu-Um, Aceh Besar, Aceh Province, Indonesia. The C. gigantea leaf extract was mixed with AgNO3 solutions at concentrations of 2, 5, and 9 mM, respectively. The mixture was stirred at 80 rpm by a magnetic stirrer for 48 hours in the dark. The change in solution color indicated the reduction of Ag+ to Ag0. The resulting AgNPs synthesized using C. gigantea leaf extract (AgNPs-LCg) exhibited cloudy grey, reddish dark brown, and light brown colors when synthesized with AgNO3 concentrations of 2, 5, and 9 mM, respectively. The particle sizes of AgNPs-LCg had maximum frequencies at 246.98 nm (synthesized using AgNO3 2 mM), 93.02 nm (synthesized using AgNO3 5 mM), and 171.25 nm (synthesized using AgNO3 9 mM). The zeta potential values of AgNPs-LCg using 2, 5, and 9 mM AgNO3 were -41.9, -40.1, and -31.4 mV, respectively. Based on the solution color, nanoparticle size, and stability value of AgNPs, it can be concluded that the use of AgNO3 at 5 mM is optimal for the green synthesis process of AgNPs-LCg.

A colorimetric chemosensor for Cu2+/Hg2+ based on a cycloruthenated 2-phenylbenzimidazole

A cyclometalated ruthenium complex (1) with 2-phenylbenzimidazole as the ligand was synthesized and used as a colorimetric chemosensor to detect Hg2+ and Cu2+. It is interesting that the presence of Hg2+ caused a blue-shifted absorption of 1 from 560 to 450 nm resulting in a solution color change from red to yellow, while the addition of Cu2+ resulted in an attenuated absorption along with the solution color changing from red to colorless. Their corresponding detection limits were calculated to be 0.25 µM for Hg2+ and 0.45 µM for Cu2+, respectively. Moreover, the slips of paper were dyed with complex 1 and then successfully used to recognize Hg2+ and Cu2+ by naked eyes, respectively. Furthermore, 1 was also used to determine Hg2+ and Cu2+ in some spiked water samples, respectively.

Dual fluorescence-colorimetric sensor based on silver nanoparticles for determination of tobramycin in its pharmaceutical preparations

The purpose of this study is to develop a dual fluorescence-colorimetric sensor for determination of the non-chromophoric drug, tobramycin using fluorescein-modified silver nanoparticles. Fluorescein is adsorbed on the surface of silver nanoparticles resulting in quenching of the fluorescence intensity of fluorescein at 513 nm. Upon addition of tobramycin to fluorescein-bound silver nanoparticles, tobramycin can displace fluorescein from the surface of nanoparticles resulting in nanoparticles aggregation and liberation of free fluorescein restoring its fluorescence. The interaction of tobramycin with fluorescein-bound silver nanoparticles is manifested by a decrease in the surface plasmon resonance band of silver nanoparticles at 395 nm, an increase in the fluorescence intensity of fluorescein at 513 nm and color change of the colloidal solution from yellow to light pink. These spectral effects are directly proportional to the concentration of tobramycin with a linearity range of 0.10 – 0.45 μg mL−1 and 0.05 – 0.45 μg mL−1 for the spectrophotometric and spectrofluorimetric methods, respectively. The proposed methods were applied for determination of tobramycin in Tobrin® ophthalmic solution with mean %recovery ± standard deviation of 99.036 ± 1.737 for the spectrophotometric method and 101.192 ± 1.315 for the spectrofluorimetric method. The optical sensor is simple, rapid, and cost-effective and can be used for determination of tobramycin in bulk and in its pharmaceutical preparations.

Effect of denture cleansers on color stability and surface roughness of denture bases fabricated from three different techniques: Conventional heat-polymerizing, CAD/CAM additive, and CAD/CAM subtractive manufacturing.

Denture base materials are commonly exposed to different denture cleansers which can affect their essential properties. This study aimed to assess the effect of denture cleansers on color stability and surface roughness of poly methyl methacrylate (PMMA) denture bases fabricated from different techniques: Conventional heat-polymerizing, CAD/CAM additive and CAD/CAM subtractive. In this in vitro study, 24 disc-shaped specimens were fabricated by the mentioned methods for each group. The initial color and surface roughness of specimens were recorded. The specimens were randomly divided into three subgroups (n = 8): a control subgroup (distilled water), and two experimental subgroups of bioactive oxygen tablet (Corega) and 1% sodium hypochlorite solution. Then they were immersed in the solutions simulating 180 days of clinical use. Color change (∆E) was measured by a spectrophotometer according to the CIE L*a*b* color space and the American National Bureau of Standards (NBS = 0.92 × ∆E). Final surface roughness was recorded by a profilometer and its change was calculated. The Kruskal-Wallis test followed by the Wilcoxon signed rank test were used for statistical analyses (α = .05). The conventional and CAD/CAM subtractive groups showed an increase in surface roughness following immersion in hypochlorite solution (p < .05). After immersion in the solutions, the highest surface roughness was noted in the conventional group, and the lowest in the CAD/CAM additive group. The CAD/CAM additive group experienced a significant color change in hypochlorite solution (p < .05) and showed the highest color change while the CAD/CAM subtractive group showed the lowest color change in all denture cleanser solutions. Although the CAD/CAM additive denture base resins had the lowest surface roughness after exposure to denture cleanser solutions, they showed significant color change, which should be taken into account. Using hypochlorite as a denture cleanser should be cautioned due to its negative effects on the surface roughness and color stability of denture base materials.

Smartphone coupled, solution, solid and vapour phase sensing of nerve agent mimic by 1,8-naphthalimide derived Schiff base

A 1,8-naphthalimide based Schiff base, SAL, comprising of n-butyl-1,8-naphthalimide and 2-hydroxysalicyaldehyde as fluorophore and receptor units, respectively, has been utilized for the efficient detection of nerve agent mimic, diethyl chlorophosphate (DCP). Upon interaction with DCP, blue shift in the UV–vis band and enhancement in emission peak of SAL was observed with detection limit of 15.4 µM based on fluorescence titration data. The sensor was capable to selectively detect various concentrations of DCP by naked eye as well as fluorescent color change in solid, solution and vapour phase in the presence of stockpile of other competitive analytes. Further, the colorimetric changes were coupled with the smartphone via a color detector app for the cost-effective, convenient and on-site detection of DCP.

High‐Contrast Optical Nitrile‐Rich Molecular Switches: Synthesis of Pyrrol‐2‐ones Containing a Butadienetricarbonitrile Fragment and Kinetics of Their Reversible Interaction with Morpholine

AbstractDirect synthesis of previously undescribed 5‐aryl‐substituted pyrrol‐2‐one derivatives containing a butadienetricarbonitrile (BDTC) acceptor was carried out. The kinetics of their reversible interaction with morpholine accompanied with high‐contrast color changes in acetonitrile solution was studied for the first time. It was found that the electronic effects of substituents in aromatic ring had a direct effect on the reaction rate and extent, that was supported by the observed linearity between the estimated equilibrium constants and the electrophilic Hammett constants.

Visual monitoring of polystyrene nanoplastics < 100 nm in drinking water based on functionalized gold nanoparticles

Nanoplastics (NPLs), of which polystyrene (PS) plastics are typical representatives, are of global concern as emerging contaminants, especially the leakage of NPLs into drinking water, which is directly related to human health. To onsite visually assess the extent of NPLs contamination in drinking water in a rapid and non-destructive manner, this work extends the application of the highly sensitive response to pH of mercaptoundecanoic acid (MUA)-functionalized gold nanoparticles (Au NPs). Further, a visual sensing method based on the binding of alkyl chains to PS NPLs with hydrophobic force to suppress pH-induced aggregation of functionalized nanoparticles was constructed. Particularly, the designed analytical strategy is a significant renewal of the first strategy for the visual detection of PS NPLs, featuring non-destructive, fast response (∼30 s), high selectivity, and detection limit (26 μg/L). Importantly, it can reliably distinguish the more hazardous PS NPLs of smaller particle size (<100 nm). Moreover, visualization-based detection observes the color change of the reaction solution from dark purple to wine red. The employment of a smartphone installed App to read the color three-channel value R further ensures the credibility of the analysis results. The proposed visual analysis strategy will provide a promising new avenue for efficient detection of surface hydrophobic NPLs and further evaluation of their particle size or shape.