A Facile Method for the Synthesis Fluorescent Zinc Chalcogenide (ZnO, ZnS and ZnSe) Nanoparticles in PS and PMMA Polymer Matrix.

A simple method for the synthesis of fluorescent zinc chalcogenide (ZnO, ZnS and ZnSe) nanoparticles directly in the transparent PMMA and PS polymer matrices were reported. Highly dispersed small spherical ZnO nanoparticles (3-5 nm) was obtained by hydrothermal reaction of PMMA/PS-Zn(acac)2H2O in toluene. ZnS and ZnSe nanoparticles were prepared by heterogeneous stirring of PMMA/PS-Zn(acac)2H2O in toluene with aqueous solution of thiourea or NaHSe. Interestingly, ZnO and ZnS-PMMA thin film showed strong fluorescence quenching upon exposure to ammonia.

Perylene Diimide Based Fluorescent Dyes for Selective Sensing of Nitroaromatic Compounds: Selective Sensing in Aqueous Medium Across Wide pH Range.

Water soluble perylenediimide based fluorophore salt, N,N'-bis(ethelenetrimethyl ammoniumiodide)-perylene-3,4,9,10-tetracarboxylicbisimide (PDI-1), has been used for selective fluorescence sensing of picric acid (PA) and 4-nitroaniline (4-NA) in organic as well as aqueous medium across wide pH range (1.0 to 10.0). PDI-1 showed strong fluorescence in dimethylformamide (DMF) (Φf = 0.26 (DMF) and moderate fluorescence in water. Addition of picric acid (PA) and 4-nitroaniline (4-NA) into PDI-1 in DMF/aqueous solution selectively quenches the fluorescence. The concentration dependent studies showed decrease of fluorescence linearly with increase of PA and 4-NA concentration. The interference studies demonstrate high selectivity for PA and 4-NA. Interestingly, PDI-1 showed selective fluorescence sensing of PA and 4-NA across wide pH range (1.0 to 10.0). Selective fluorescence sensing of PA and 4-NA has also been observed with trifluoroacetate (PDI-2), sulfate (PDI-3) salt of PDI-1 as well as octyl chain substituted PDI (PDI-4) without amine functionality. These studies suggest that PA and 4-NA might be having preferential interaction with PDI aromatic core and quenches the fluorescence. Thus PDI based dyes have been used for selective fluorescent sensing of explosive NACs for the first time to the best our knowledge.

Off-on Fluorescent Sensor from On-off Sensor: Exploiting Silver Nanoparticles Influence on the Organic Fluorophore Fluorescence.

Turn-off fluorescence of organic fluorophore, 2-{[4-(2H-Naphtho[1,2-d][1,2,3]triazol-2-yl)-phenyl]carboxylic acid (NTPC), with metal ions (Fe(3+), Cu(2+), Pb(2+)) was converted into turn-on fluorescent sensor for biologically important Zn(2+), Cu(2+) and Fe(3+) metal ions in aqueous solution at ppb level by exploiting strong fluorescence quenching phenomena of metal nanoparticles when organic fluorophores assembled in the vicinity of metallic surface. Amino acid attached phenolic ligands (L) were used as reducing as well as functional capping agents in the synthesis of silver nanoparticles (AgNPs). The hydrogen bonding functionality of L facilitated the assembling of NTPC in the vicinity of metallic surfaces that leads to complete quenching of NTPC fluorescence. The strong and selective coordination of L with metal ions (Zn(2+), Cu(2+) and Fe(3+)) separates the NTPC from the AgNPs surface that turn-on the NTPC fluorescence. HR-TEM and absorption studies confirm the metal coordination with L and separation of NTPC from the AgNPs surface. Mn(2+) showed selective red shifting of NTPC fluorescence after 12 h with all sample. Effects of different amino acid attached phenolic ligands were explored in the metal ion sensitivity and selectivity. This approach demonstrates the multifunctional utility of metal NPs in the development of turn-on fluorescence sensor for paramagnetic heavy metal ions in aqueous solution. ᅟ

Substitutional group dependent colori/fluorimetric sensing of Mn(2+), Fe(3+) and Zn(2+) ions by simple Schiff base chemosensor.

Schiff base is one of the easiest synthesizable chemosensor and exhibit strong coordination with metal ions; the property that has been vastly exploited for metal ions sensing. Simple Schiff base chemosensors (1a-d and 2a-d) were synthesized and demonstrated substitutional group dependent colorimetric sensing of metal ions. Chemosensor without (1a, 2a) and OCH3 substitution (1b, 2b) did not show any significant colour change for metal ions. However, a highly selective colorimetric change (colourless to pink) for Mn(2+) ions (10(-6)M) was observed with diethylamine substituted 1c, 2c. Hydroxyl substitution (1d, 2d) leads to selective colorimetric sensing (colourless to orange) of Fe(3+) ions (10(-6)M). PVA thin films of 2c/2d were fabricated and demonstrated selective colorimetric sensing of Mn(2+) and Fe(3+) ions. The practical applicability of the synthesized chemosensors were also demonstrated by performing selective colorimetric sensing of Mn(2+) and Fe(3+) ions in real samples such as tap, ground, pond and river water. Effect of substitution on the fluorescence selectivity of Zn(2+) has also been investigated.

Surface functionalized fluorescent CdS QDs: selective fluorescence switching and quenching by Cu(2+) and Hg(2+) at wide pH range.

Fluorescent CdS QDs surface functionalized with organic functional unit, N-(2-hydroxybenzyl)-cysteine (L), has been synthesized using simple wet chemical approach in a single step. The as-prepared L-CdS QDs showed good fluorescence at 542 nm. Fluorescence sensor studies of L-CdS QDs showed selective fluorescence switching (542-600 nm) for Cu(2+) ions and quenching for Hg(2+) ions in aqueous solution. High selectivity of L-CdS QDs for Cu(2+) ions have been confirmed by interference studies. Interestingly, L-CdS QDs showed enhancement in the fluorescence intensity (4-fold) upon reducing pH from 2.0 to 10.0 without changing λmax. Importantly, selective fluorescent switching and quenching for Cu(2+) and Hg(2+) was observed from 2.0 to 10.0 pH range. The practical application of L-CdS QDs fluorescence sensing for Cu(2+) and Hg(2+) have also been demonstrated in real samples such as river, pond, tap and ground water.

Synthesis of new colori/fluorimetric chemosensor for selective sensing of biologically important Fe³âº, Cu²âº and Zn²âº metal ions.

New Schiff base chemosensors (1 and 2) based on aryl ether amine were synthesized and demonstrated positional isomer and functional group dependent colori/fluorimetric sensing of Fe(3+), Cu(2+) and Zn(2+) at ppm level. Methoxy salicylaldehyde based chemosensor 1 exhibited selective colorimetric sensing of Fe(3+) whereas 2-hydroxy naphthaldehyde based chemosensor 2 showed selective disappearance of yellow color for Cu(2+) ions. Interestingly, both 1 and 2 exhibited a highly selective strong turn-on fluorescence for Zn(2+). The significance of COOH group in 1 and 2 for Zn(2+) turn-on fluorescence sensing has been confirmed by structure-property studies. Concentration dependent studies of 1 and 2 indicate that Fe(3+), Cu(2+) and Zn(2+) can be detected up to 10 µM. The formation of 1:1 Zn(2+) and chemosensor (1 and 2) confirmed by NMR studies. High selectivity of 1 and 2 was demonstrated by interference studies in presence of different metal ions.

Selective turn-on fluorescence for Zn(2+) and Zn(2+)+Cd(2+) metal ions by single Schiff base chemosensor.

Chemosensor based on Schiff base molecules (1, 2) were synthesized and demonstrated the selective fluoro/colorimetric sensing of multiple metal ions (Mn(2+), Zn(2+) and Cd(2+)) in acetonitrile-aqueous solution. Both 1 and 2 showed a highly selective naked-eye detectable colorimetric change for Mn(2+) ions at 10(-7) M. Fluorescence sensing studies of 1 and 2 exhibited a strong fluorescence enhancement (36 fold) selectively upon addition of Zn(2+) (10(-7) M, λmax=488 nm). Fluorescence titration and single crystal X-ray analysis confirmed the formation of 1:1 molecular coordination complex between 1 and Zn(2+). Interestingly, a rare phenomenon of strong second turn-on fluorescence (190 fold, λmax=466 nm) was observed by the addition of Cd(2+) (10(-7) M) into 1+Zn(2+) or Zn(2+) (10(-7) M) into 1+Cd(2+). Importantly both 1 and 2 exhibited different fluorescence λmax with clearly distinguishable color for both Zn(2+) and Cd(2+).

ADAMIS: a database for medical information systems.

This paper describes the design and implementation of ADAMIS ('A database for medical information systems'). ADAMIS is a relational database management system for a general hospital environment. Apart from the usual database (DB) facilities of data definition and data manipulation, ADAMIS supports a query language called the 'simplified medical query language' (SMQL) which is completely end-user oriented and highly non-procedural. Other features of ADAMIS include provision of facilities for statistics collection and report generation. ADAMIS also provides adequate security and integrity features and has been designed mainly for use on interactive terminals.