Picric Acid In Aqueous Solution Research Articles

PECULIARITIES OF REVEALING AND ESTIMATION OF AUSTENITIC GRAIN IN STRUCTURAL ALLOYED STEELS

Purpose. Establishing effective and correct techniques for detecting the grain structure in structural medium-carbon steels taking into account the recommendations of modern standards (ДСТУ ISO, ASTM, ГОСТ) with the aim of reliably determining the austenitic grain size and putting into operation of metal with the well-known and required, according to the normative technical documentation (technical requirements, drawings) quality.
 Research methods. Metallographic analysis of microstructure and evaluation of the austenitic grain size were carried out by comparing the image revealed on polished and etched using various chemical reagents microsections of heat-treatable steel 40KHN2МА-Ш with etalon of scale of standard.
 Results. Studies of structural alloyed steel 40ХН2МА-Ш found that the most effective etchant reagent, which best detects initial austenitic grain boundaries in medium-carbon alloyed steels, is a standard reagent - a saturated aqueous solution of picric acid. As a result of etching in this reagent, a visible image of the grain structure is formed in the form of a clear contrast of light areas of the grain body and dark lines of the grain boundaries, which allows a correct comparison of the structure with the images of the standards on the scales.
 Scientific novelty. On the example of heat- treatable steel 40ХН2МА-Ш, the ways of further development of ideas regarding the choice of an effective chemical reagent are considered for the purpose of detecting and forming a visible grain structure in accordance with the requirements of methodical standards in structural medium-carbon steels, proper and reliable estimation of austenitіс grain size using standard scale.
 Practical value. A correct procedure for detecting the initial austenite grain is proposed, which allows to reliably determine the grain size and quality from this parameter of various structural steels including for the production of responsible parts of aircraft and spacecraft.

Crystal structure of 2-(morpholino)ethyl-ammonium picrate monohydrate.

The title compound, C6H15N2O+·C6H2N3O7 -·H2O, was synthesized via slow evaporation of an aqueous solution of picric acid with the substituted morpholine base and crystallized with one cation (C6H15N2O)+, one anion (C6H2N3O7)- and a water mol-ecule in the asymmetric unit. The morpholine ring in the cation adopts a chair conformation. The structure is stabilized by C-H⋯O, O-H⋯O, O-H⋯N and N-H⋯O hydrogen-bonding inter-actions and π-π stacking. The inter-molecular inter-actions of the synthesized compound were qu-anti-fied by Hirshfeld surface analysis.

Two multifunctional luminescent cobalt metal-organic frameworks for selectively and sensitively sensing of Cu2+, MnO4- and picric acid in water

Developing novel metal-organic frameworks (MOFs) and exploring their luminescent applications gains continuous concern. Herein, based on tetraphenylpyrazine fluorophore, two cobalt metal-organic frameworks (MOFs), denoted as {Co(HCOO)(Tipp)·H2O}n(1) and {Co(Tipp)0.5A}n(2) (Tipp ​= ​2, 3, 5, 6-tetrakis[4-[(1H-imidazole-1-yl)-methyl]phenyl]pyrazine, H2A ​= ​4, 4'-oxybisbenzoic acid), have been prepared under hydrothermal condition. Structural analysis indicates that 1 has a (4, 6)-connected 3D seh network with the point symbol of {3∙42∙52∙6}{32∙42∙52∙64∙74∙8}. 2 shows a (2, 4)-connected 2D framework with a new Schläfli symbol of {42∙82∙102}{42∙83∙10}2{4}2. Significantly, 1 and 2 can be employed as multifunctional sensors for selective and sensitive detection of Cu2+, MnO4- and picric acid in aqueous solution by fluorescence quenching. The limits of detection (LODs) for Cu2+, MnO4- and picric acid were down to 10-7 ​M and quenching constant (Ksv) values reach the level of 105 ​M-1. Moreover, the two sensors show good recyclability and can respond to analytes in a wide pH range.

Lanthanide luminescence based probe for detection of picric acid

Europium fluorescence is significantly enhanced through ligand sensitization using aromatic benzene mono and di carboxylic acids as ligands in aqueous solution. By optimizing metal to ligand ratio and solution pH, it is established that the enhancement is maximum with iso-phthalic and tere-phthalic acid. Phosphorescence of isophthalic acid is recorded and its triplet energy level is found to be at 25633 cm-1; just above the fluorescing energy level of Eu3+. On complexation with these ligands though the europium luminescence is enhanced by orders of magnitude, the europium lifetime increased marginally. Addition of picric acid resulted in the quenching of europium luminescence in europium-isophthalic acid complex. Based on this quenching, a fluorimetric method is developed for the estimation of picric acid in aqueous solution. Picric acid in aqueous solution could be estimated down to 0.23 ppm. Common cations and anions found in natural waters did not interfere in the analysis. The precision in measurement is within 5 % RSD in the entire range of measurement.

A highly stable terbium metal-organic framework for efficient detection of picric acid in water

A highly stable fluorescent terbium MOF (Tb4(paip)6·1.2H2O, paip = 5-(1H-pyrazole-4-yl)isophthalate) showing a sharp green emission (545 nm) and a quantum yield of 21.0% was successfully synthesized. This compound is shown to be a recyclable sensor for detecting picric acid in aqueous solution with both high sensitivity and selectivity, attributed to the electron transfer quenching mechanism.

Water-soluble polyaromatic-based imidazolium for detecting picric acid: Pyrene vs. anthracene

Highly water-soluble fluorescent polyaromatic-based imidazolium compounds capable of detecting a wide-range of nitroaromatics, e.g., nitrophenols and picric acid in aqueous solution with fully quenched fluorescence are reported. The two probes contained an anthracene and pyrene group with the increased size and angularity of the pyrene ring in pyrene-based imidazolium (PIM) raising the hydrophobicity or π-π stacking and sensitivity of the probe towards all mono-, di-, and trinitrophenols even under harsh conditions (pH 4-8). The high affinity for nitrophenols was confirmed by single crystal X-ray crystallography. Time-dependent density functional theory (TD-DFT) reveals cation-anion interactions between the imidazolium and picrate ions causing fluorescent quenching through PET and charge transfer involving a dark S1 excited state.

Nitrogen/sulfur-co-doped carbon quantum dots: a biocompatible material for the selective detection of picric acid in aqueous solution and living cells.

Here, a fast and eco-friendly one-pot hydrothermal technique is utilized for the synthesis of nitrogen/sulfur-co-doped fluorescent carbon quantum dots (NS-CQDs) from a simple precursor of citric acid (CA) and thiosemicarbazide (TSC). The obtained NS-CQDs exhibited strong blue emission under UV light, with fluorescence quantum yield (QY) of ~37.8%. The Commission internationale de l'eclairage (CIE) coordinates originated at (0.15, 0.07), which confirmed the blue fluorescence of the synthesized NS-CQDs. Interestingly, the prepared NS-CQDs were successfully used as a selective nanoprobe for the monitoring of environmentally hazardous explosive picric acid (PA) in different nitro- and non-nitro-aromatic derivatives of PA. The mechanism of the NS-CQDs was also explored, and was posited to occur via the fluorescence resonance electron transfer (FRET) process and non-fluorescent complex formation. Importantly, this system possesses excellent biocompatibility and low cytotoxicity in HeLa cervical cancer cells; hence, it can potentially be used for PA detection in analytical, environmental, and pathological applications. Furthermore, the practical applicability of the proposed sensing system to pond water demonstrated the feasibility of our system along with good recovery. Graphical abstract.

A facile one step hydrothermal synthesis of carbon quantum dots for label -free fluorescence sensing approach to detect picric acid in aqueous solution

In this work, a facile one step approach has been applied for the synthesis of nitrogen and sulphur co-doped water soluble carbon quantum dots (NS-CQDs) through hydrothermal treatment of L-Lysine and thiourea. The obtained NS-CQDs have a high quantum yield (QY) of 53.19 % and emit strong blue fluorescence under UV light excitation of wavelength 365 nm. The morphology of NS-CQDs is spherical in shape and their sizes are distributed in the range 5–8 nm with average diameter 6.86 nm. Moreover the NS-CQDs show excitation dependent emission behavior due to quantum confinement effect. Additionally, NS-CQDs serve as a fluorescent probe for the selective and sensitive detection of picric acid (PA) in aqueous solution. A good linear response to PA in the concentration range 1–10 μM with a detection limit 0.24 μM has been obtained. The high selectivity of PA by NS-CQDs is suggested to arise from fluorescence resonance energy transfer (FRET) mechanism. Finally these NS-CQDs fluorescent probes have been examined in real water sample by measuring the concentration of PA in tap water.

Pyrenoviologen-based fluorescent sensor for detection of picric acid in aqueous solution

Two highly emissive pyrenoviologen derivatives were synthesized and used to fabricate fluorescent sensors for detection of picric acid (PA) with good sensitivity and selectivity. The sensitivity of the sensor was attributed to the specific electrostatic association effect of the cationic pyrenoviologens to the picrate anions, which also gave the sensor special selectivity among other compounds with similar structure. The electron transfer between them was attributed to the fluorescence response. Fluorescence lifetime measurements revealed that the quenching is static in nature. The novel and efficient pyrenoviologen derivatives-based sensors offered a strategy to fabricate real-life PA sensor.

Nanostructured CeO2 for selective-sensing and smart photocatalytic applications

Well crystalline CeO2 nanoparticles have been successfully synthesized via solution combustion synthesis (SCS) using (NH4)2[Ce(NO3)6] and C4H6O6 as oxidizer and fuel. The structural characteristics of as-synthesized material were investigated in terms of FESEM, HRTEM, EDS, XRD, FTIR and UV–Vis spectroscopy techniques. The surface area of synthesized CeO2 nanoscale material was obtained from BET plot. Results showed a pure, well-crystallized, flake-like mesoporous material to be formed with crystallite size of 18.86 nm. The focus of this study was to investigate the application of as-synthesized CeO2 nanomaterial for sensing and photocatalytic degradation of picric acid (PA) in its aqueous solution. It was found to be highly selective for PA detection in aqueous solution when compared with other aromatic compounds. Detection limit (0.52 µM) for PA when compared with earlier studies was found to be much better. In addition, 0.05 gm of as-synthesized CeO2 nanomaterial is found to be optimum amount ensuring maximum catalytic photodegradation of 10 ppm PA in aqueous solution. These experimental findings point out that as-synthesized CeO2 nanomaterial can be efficiently used as an effective chemical sensor and photocatalyst.

Electrospun nanofibrous membrane based on AIE-active compound for detecting picric acid in aqueous solution

An electrospun membrane (CB-PS) was prepared by electrospinning technique from a solution of aggregation induced emission (AIE) active compound 5-(N-carbazole styryl)-1,3-dimethyl-barbituric acid (CB) and polystyrene (PS) in DMF/THF. The membrane was electrospun upon amino-functionalized glass [G-NH2], producing a fluorescent sensor [CB-PS]/[G-NH2] for detecting picric acid (PA). The AIE-active compound were highly photostable and the sensor [CB-PS]/[G-NH2] exhibited high selectivity and sensitivity for the detection of PA over nitroaromatics (NACs) in aqueous phase. The quenching constant (KSV) to PA was obtained to be 3.29 × 104 M−1 in aqueous phase with a limit of detection (LOD) up to 228 ppb. Selectivity study demonstrates that common interferents have an insignificant effect on the emission intensity of the fluorescent nanofibers in aqueous phase, while reusability study indicates that the fluorescent nanofibers can be regenerated. Real water sample was also tested, and negligible matrix effect on explosives detection was observed. The fluorescence quenching by PA can be attributed to the photo-induced electron transfer (PET) in the quenching process. This research provides new insights into the application of AIE-active materials in fluorescent nanofibrous explosive sensor.

Inner filter effect based selective detection of picric acid in aqueous solution using green luminescent copper nanoclusters

Designing superior probes to detect trace amounts of picric acid (PA) is of huge importance for homeland security and environmental protection.

Aggregation-enhanced FRET-active conjugated polymer nanoparticles for picric acid sensing in aqueous solution

A conjugated polymer with aggregation-enhanced FRET activity has been used for fluorescence sensing of picric acid in aqueous solution.

Rapid synthesis of a hyperfluorescence 2-pyridone derivative as a fluorescent molecular sensor for picric acid

In this article, a hyperfluorescence 2-pyridone derivative (D-TPCA) has been synthesized within 5min by the microwave-assistant heat treatment of the aqueous mixture of citric acid and 2-aminoethanethiol hydrochloride. The as-prepared D-TPCA exhibited good aqueous solubility and excellent fluorescent property with a quantum yield of 89.9%. Because the fluorescence of D-TPCA could be effectively quenched by picric acid (PA), D-TPCA could be served as a “turn-off” fluorescence sensor for PA in aqueous solution. The proposed sensing method permitted a selective and sensitive detection of PA in a linear range of 0–45μM with a detection limit of 56.0nM. The determination results of PA in real water samples with a recovery range of 95.4–107.3% confirmed a good analytical performance of this sensor. In addition, the possible sensing mechanism has been discussed in detail.

Characterization of potassium bromide crystals grown in the aqueous solution of picric acid

Potassium bromide crystals were grown in the aqueous solution of picric acid by slow evaporation technique at room temperature. X-ray Diffraction (XRD) analysis ensures that the grown sample is in Fm3m space group and FCC structure. Energy Dispersive X-ray Spectroscopy (EDX) reveals the presence of elements in the title compound. UV–Vis-NIR spectrum reveals that the grown sample is a promising nonlinear optical (NLO) material. FTIR analysis confirms the functional groups present in the sample. The thermogravimetric (TG) and differential thermogravimetric (DTA) analyses ensure that the sample material is thermally stable up to 160°C. The second harmonic efficiency of the sample is 1.3 times greater than that of standard KDP. The mechanical strength of the grown sample is estimated by Vickers microhardness tester. The electrical properties were investigated by impedance analysis and the results of various studies of the grown crystals are discussed.

Self-Assembled Pentacenequinone Derivative for Trace Detection of Picric Acid

Pentacenequinone derivative 3 forms luminescent supramolecular aggregates both in bulk as well as in solution phase. In bulk phase at high temperature, long-range stacking of columns leads to formation of stable and ordered columnar mesophase. Further, derivative 3 works as sensitive chemosensor for picric acid (PA) and gel-coated paper strips detect PA at nanomolar level and provide a simple, portable, and low-cost method for detection of PA in aqueous solution, vapor phase, and in contact mode.

Amine-capped carbon dots as a nanosensor for sensitive and selective detection of picric acid in aqueous solution via electrostatic interaction

In this study, a simple and low toxicity method based on water-soluble amine-capped carbon dots as a nanosensor for sensitive and selective detection of picric acid (PA) in water was developed. We found that PA could remarkably quench the fluorescence signal of the amine-capped carbon dots in water, while other nitroaromatic explosives and common reagents only caused little fluorescence quenching. The detection limit of the amine-capped carbon dots towards PA in aqueous solution was about 1 μM. The results indicate that the strong electrostatic interaction from an anion–cation pair between PA and the carbon dot surface could enhance the fluorescence selective response towards PA in aqueous solution.

Triphenylene derivatives: chemosensors for sensitive detection of nitroaromatic explosives

New triphenylene derivatives 3 and 5, synthesized using a Suzuki-Miyaura coupling protocol and by a click reaction respectively, serve as potent chemosensors for various electron deficient nitroaromatic explosives, such as picric acid, trinitrotoluene, dinitrotoluene and dinitrobenzene. Derivative 5 exhibits a more sensitive response towards the nitroaromatics compared to derivative 3 due to its ordered organization. Furthermore, the solution coated strips of derivative 3 and gel coated strips of derivative 5 can detect picric acid in the range of 14 pg cm(-2), thus providing a simple and low cost method for the detection of picric acid in aqueous solution and in a contact mode.

New method for testing the absorbency of surgical dressings.

Absorbent cellulose dressings have been tested by immersion in a standard aqueous solution of picric acid followed by standard draining, elution of the picric acid, and measurement of the absorbance of the yellow colour at 355 nm. Six samples of gauze were graded by this procedure, and two considered unsatisfactory, despite all sinking in less than 10s. Filmated gauzes and unwoven dressings required greater dilution for the absorbance readings, reflecting their different structures.

Grain refinement during the γ-α transformation in a low-carbon steel

samples were quenched in water) corresponded to every ferrite grain structure. Austenite and ferrite grain structures were revealed through etching of polished sections in a boiling saturated aqueous solution of picric acid with surfactant additives and in a 4% solution of nitric acid in alcohol, respectively. Images of microstructures were taken at a resolution of 1536 × 1024 on a Neophot 21 microscope with an optical attachment and a Canon EOS 300D digital video camera. Ferrite and austenite grains were measured at magnifications of × 100‐500 by the random intercept method (at least 500‐600 grains per version) using an Epiquant semi-automatic analyzer. The results were processed using the Image Expert Pro program. The average sizes of the initial ( D γ ) and final ( d α ) grains, their ratios (transformation coefficients k ), and their errors were calculated. The change in the transformation coefficient (and the change in the ferrite grain size) as a function of the scale of the initial austenite grain and the cooling rate was estimated for the steel of every grade, k = f ( D γ , w )