Prithidipa Sahoo

Color response of tri-armed azo host colorimetric sensors and test kit for fluoride.

Five new chromogenic tripodal receptors (2a-e) containing electron withdrawing and donating groups appended to the azophenol moiety were synthesized, characterized, and their chromogenic behaviors toward various anions were investigated. These tripodal receptors showed a distinct color change only when treated with fluoride ions in CH(3)CN solution. Yet, other anions such as Cl(-), Br(-), I(-), NO(3)(-), ClO(4)(-), AcO(-), HSO(4)(-), and H(2)PO(4)(-) could not cause any color change. Thus, the receptors 2a-e can be used as a colorimetric chemosensor for the determination of fluoride ion. In addition, (1)H NMR experiments were carried out to explore the nature of interaction between tripodal receptors and fluoride. Finally, analytical application and the use of test strip of the receptor 2b to detect fluoride was also reported.

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions.

Summary A novel indolocarbazole-based chemosensor 1 containing hydrogen bond donor moieties has been established as a selective colorimetric and fluorometric sensor for F− in CH3CN/H2O (4:1 v/v). Upon the addition of a series of tetrabutylammonium salts to receptor 1 in aqueous CH3CN, only when the counter ion was F− was a significant color change (from light violet to dark orange) observed.

A BODIPY/pyrene-based chemodosimetric fluorescent chemosensor for selective sensing of hydrazine in the gas and aqueous solution state and its imaging in living cells

A BODIPY-based pyrenebutyrate-linked (BPB) chromogenic and fluorogenic probe was synthesized and characterized for the specific detection of hydrazine. In the presence of hydrazine, BODIPY-based pyrenebutyrate was selectively deprotected, producing switch off meso-phenoxyBODIPY along with a color change from yellow to brown, allowing colorimetric detection of hydrazine by the naked eye. Selectivity experiments proved BPB has excellent selectivity to hydrazine over other environmentally abundant ions and common amine-containing species. Probe BPB was also successfully applied in vapor hydrazine detection into a solid state over other interfering volatile analytes. Furthermore, the probe BPB coated with silica gel TLC plates could act as a visual and fluorimetric probe for hydrazine vapor detection. The probe (BPB) has been shown to detect hydrazine up to 1.87 μM at pH 7.4. DFT and TDDFT calculations were performed in order to demonstrate the sensing mechanism and the electronic properties of the probe and hydrazinolysis product. BPB can also be used for the detection of hydrazine in Vero cells without appreciable interference from other biologically abundant analytes.

A highly sensitive fluorescent probe for detection of hydrazine in gas and solution phases based on the Gabriel mechanism and its bioimaging

A new probe 2-benzo[1,2,5]thiadiazol-4-yl-isoindole-1,3-dione (BTI) based on the Gabriel reaction mechanism was synthesized and characterized for the specific detection of hydrazine with high selectivity against other amines in an organo-aqueous solution. Upon hydrazinolysis of BTI in the presence of hydrazine in a H2O–DMSO (4 : 6, v/v) solution (10 mM HEPES buffer, pH 7.4) at room temperature, the chemosensor produces fluorescent aminobenzthiadiazole with a maximum emission at 498 nm along with a color change from colorless to green, allowing selective colorimetric and fluorometric detection of hydrazine by the naked eye. Probe BTI was also successfully applied in vapor phase hydrazine detection into a solid state over other interfering volatile analytes. Furthermore, the probe BTI coated with silica gel TLC plates could act as a visual and fluorimetric probe for hydrazine vapor detection. The experimental detection limit of hydrazine is 2.9 ppb, which is well below the accepted limit (10 ppb) for hydrazine set by the U.S. Environmental Protection Agency (EPA). DFT and TDDFT calculations were performed in order to demonstrate the sensing mechanism and the electronic properties of probe and hydrazinolysis products. Additionally, probe BTI could also be applied for the imaging of hydrazine in living cells.

Pyrene appended thymine derivative for selective turn-on fluorescence sensing of uric acid in live cells

A new ‘turn-ON’ fluorescent probe, pyrene appended thymine acetamide (PTA), with high sensitivity and selectivity for the detection of uric acid (UA) was developed and first time imaging of uric acid in living cells in water was achieved. 1H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between probe PTA and UA.

Aminomethylpyrene-based imino-phenols as primary fluorescence switch-on sensors for Al3+ in solution and in Vero cells and their complexes as secondary recognition ensembles toward pyrophosphate

Three aminomethylpyrene-based salicyl-imines, viz. L1, L2 and L3 were synthesized and characterized and their recognition of biologically relevant Mn+ ions was studied. These three receptors were shown to be selective and sensitive for Al3+ among the 13 metal ions studied in a HEPES buffer medium by fluorescence, absorption, and visual emission color change with detection limits of 3.60, 2.13 and 2.16 μM, respectively, by L1, L2 and L3. The interaction of Al3+ with the three receptors (L1, L2 and L3) has been further supported by absorption studies, and the stoichiometry of the complex formed (1 : 1) has been established on the basis of emission and ESI-MS. Competitive ion titrations carried out reveal that the Al3+ can be detected even in the presence of other metal ions of bio importance. The structure of the aluminium complexes and their mode of interactions were established by DFT calculations. TDDFT calculations were performed in order to demonstrate the electronic properties of receptors. Microstructural features of L2 and its Al3+ complex have been measured by AFM. Moreover, the utility of the receptors L1, L2 and L3 in showing aluminium recognition in live cells has also been demonstrated using Vero cells as monitored by fluorescence imaging. In situ prepared [AlL1] and [AlL3] complexes were found to be sensitive and selective toward phosphate-bearing ions and molecules and in particular to pyrophosphate (PPi) among the other 15 anions studied; however, [AlL2] was not sensitive toward any of the anions studied.

Optimisation of tribological performance of electroless Ni–B coating using Taguchi method and grey relational analysis

Abstract The present study utilises Taguchi based grey relational analysis in order to find the optimal tribological condition (combination of load, speed and time) to minimise coefficient of friction and wear of electroless Ni–B coating. A grey relational grade is used as performance index to study the behaviour of electroless Ni–B coating with respect to friction and wear characteristics. An L27 orthogonal array is used so that the main effects as well as the interaction effects of the factors can be studied effectively. It is found that all the three test parameters have significant influence on friction and wear behaviour of Ni–B coating. Moreover significant amount of interaction is found to exist between load and speed. The coating is characterised using scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction analysis. The wear mechanism is also studied and found to be abrasive in nature.

Molecular recognition of caffeine in solution and solid state

The molecular recognition of caffeine in both solution and solid state is important to understand different enzymatic reactions i.e., enzyme-substrate interactions, immunological reactions in vivo, selective host-guest complexation and catalytic reactions in bio-mimetic chemistry. The weak intermolecular forces in recognition system direct the molecules toward self-linking in supramolecular engineering in the chemistry of life and material science. In this contribution, it has been illustrated the immense variety of receptors that have been designed for caffeine recognition in both solid and solution phase. The binding studies for the recognition of caffeine are reported by different research groups including our group. It is important to understand the goal of developing artificial molecular receptors, capable of binding very efficiently and very selectively with caffeine which is described elaborately in this context. The modern bioorganic chemistry concerns the design of synthetic molecules that mimic various aspects of enzyme chemistry and to understand their essential roles in biological systems. The stimulating effect of caffeine is not only exploited in nutrient technology but also in cosmetics and pharmaceuticals, which accounts for the economic importance of this particular additive. Although caffeine was first time isolated by Ferdinand Runge from coffee beans almost 200 years ago, it still has some surprise in hoard.

First theophylline-based ratiometric fluorescent synthetic receptor for selective recognition of dihydrogenphosphate and biological phosphate ions.

We have developed a new ratiometric fluorescent chemosensor 1 based on xanthine alkaloid theophylline moiety for the detection of dihydrogen phosphate and ATP. The chemosensor 1 selectively recognizes tetrabutylammonium dihydrogen phosphate in CH(3)CN/H(2)O (9:1) by exhibiting a significant decrease in the emission of naphthalene and its sensing properties regarding ATP and other related phosphate species were evaluated. The anion binding properties of 1 were evaluated by (1)H NMR, UV-vis, and fluorescence spectroscopic methods.

Carbazole-driven ratiometric fluorescence turn on for dual ion recognition of Zn2+ and Hg2+ by thiophene-pyridyl conjugate in HEPES buffer medium: spectroscopy, computational, microscopy and cellular studies

Abstract Carbazole-based thiophene-pyridyl conjugate (L) was synthesised and characterised. The complexation between L with Zn2+ and Hg2+ was studied in HEPES buffer medium by fluorescence, absorption and visual colour change with the detection limit of ~3.7 and ~4.8 μM, respectively. The L detects Zn2+ by bringing ratiometric change in the fluorescence signals at 418 and 515 nm, but in the case of Hg2+, the signals are observed at 418 and 365 nm, while no new band is observed at 515 nm. The structure of L has been established by single-crystal XRD and that of complexes [ZnL] and [HgL] by density functional theory calculations. TDDFT calculations were performed in order to demonstrate the electronic properties of receptors and their zinc and mercury complexes. The isolated fluorescent complexes [ZnL] and [HgL] were found to be sensitive and selective towards phosphate-bearing ions and sulfide ions, respectively, among the other anions studied. The nanostructural features such as shape and size obtained using atomic force microscopy distinguish L from its complexes formed between L and Zn2+ from that formed with Hg2+. Moreover, the utility of the conjugate L in showing the zinc recognition in live cells has also been demonstrated using RAW cells as monitored by fluorescence imaging.