Bioconjugated graphene oxide-based Raman probe for selective identification of SKBR3 breast cancer cells.

In this article, we demonstrate the use of bio-conjugated 2D graphene oxide (bio-GO) nanostructure to probe breast cancer cell (SKBR3) with excellent discrimination over other types of circulating tumor cells. We distinctly observed that bio-GO nanostructure targets and bind SKBR3 cell selectively in the cell mixture. Longer incubation of SKBR3 cell with bio-GO causes Raman signal "turn off" when excited with 532 nm laser. This is attributed to penetration of the bio-GO through the plasma membrane of the cell by generating transient hole. Extraction of GO after cell digestion also support the internalization rubric of 2D graphene through cell membrane. Our experimental data with the HaCaT healthy cell line, as well as with LNCaP prostate cancer cell line clearly demonstrated that this Raman scattering assay is highly selective to SKBR3. The mechanism of selectivity and the assay's response change have been verified and discussed utilizing fluorescence properties of GO and various other techniques. The experimental results open up a possibility of new label free Raman scattering assay, for reliable diagnosis of cancer cell lines by monitoring "turn-off" of the Raman signal from Bio-GO nanostructure.

Alizarin Dye based ultrasensitive plasmonic SERS probe for trace level Cadmium detection in drinking water.

Alizarin functionalized on plasmonic gold nanoparticle displays strong surface enhanced Raman scattering from the various Raman modes of Alizarin, which can be exploited in multiple ways for heavy metal sensing purposes. The present article reports a surface enhanced Raman spectroscopy (SERS) probe for trace level Cadmium in water samples. Alizarin, a highly Raman active dye was functionalized on plasmonic gold surface as a Raman reporter, and then 3-mercaptopropionic acid, 2,6-Pyridinedicarboxylic acid at pH 8.5 was immobilized on the surface of the nanoparticle for the selective coordination of the Cd (II). Upon addition of Cadmium, gold nanoparticle provide an excellent hotspot for Alizarin dye and Raman signal enhancement. This plasmonic SERS assay provided an excellent sensitivity for Cadmium detection from the drinking water samples. We achieved as low as 10 ppt sensitivity from various drinking water sources against other Alkali and heavy metal ions. The developed SERS probe is quite simple and rapid with excellent repeatability and has great potential for prototype scale up for field application.

MEISENHEIMER COMPLEX BETWEEN 2,4,6-TRINITROTOLUENE AND 3-AMINOPROPYLTRIETHOXYSILANE AND ITS USE FOR A PAPER-BASED SENSOR.

2,4,6-Trinitrotoluene (TNT) forms a red-colored Meisenheimer complex with 3-aminopropyltrenthoxysilane (APTES) both in solution and on solid phase. The TNT-APTES complex is unique since it forms yellow-colored complexes with 2,4,6-trinitrophenol and 4-nitrophenol, and no complex with 2,4-dinitrotoluene. The absorption spectrum of TNT-APTES has two absorption bands at 530 and 650 nm, while APTES complexes with 2,4,6-trinitrophenol and 4-nitrophenol have absorption maxima at around 420 nm, and no absorption change for 2,4-dinitrotoluene. The TNT-APTES complex facilitates the exchange of the TNT-CH3 proton/deuteron with solvent molecules. The red color of TNT-APTES is immediately visible at 1 µM of TNT.

A surface enhanced Raman scattering probe for highly selective and ultra sensitive detection of iodide in water and salt samples.

Iodine is a biophilic and essential trace element for all life and especially for vertebrates, which require it to produce indispensable thyroid hormones in their thyroid glands. As a result, the adequate measurement of iodine in water and food samples is crucial to lead a healthy life. Motivated by its importance, this is the first time in the literature that the highly selective and ultra sensitive (30 ppt limit) surface enhanced Raman scattering (SERS)-based detection of iodide ions (I(-)) from environmental and food samples has been reported. The desired sensitivity and selectivity has been achieved by measuring the change in the SERS intensity originating from Rh6G-adsorbed 30 nm gold nanoparticles (GNPs) upon the addition of I(-). The strong chemical affinity offered by I(-) towards the gold surface results in extra negative charge being deposited on it. As a result, the GNP surface attracts a greater number of positively charged Rh6G molecules and induces a marked increase in the number of hot spots through aggregation, providing a significant enhancement of the Raman signal intensity. The oxidation of I(-) to molecular iodine (I(2)) by hydrogen peroxide (H(2)O(2)) is employed for the successful screening of the bromide ion (Br(-)) which shows substantial interference at higher concentrations.

Sensitive and selective detection of trivalent chromium using Hyper Rayleigh Scattering with 5,5'-dithio-bis-(2-nitrobenzoic acid)-modified gold nanoparticles.

Hyper Rayleigh Scattering (HRS) and absorption spectral assays using surface-modified gold nanoparticles (AuNP) have been developed for sensitive and selective detection of trivalent chromium (Cr3+) from other metal ions including hexavalent chromium (as Cr2O72-). Gold nanoparticles of 13 nm, covalently attached with 5,5'-dithio-bis-(2-nitrobenzoic acid) (AuNP-DTNBA), is used as a probe for both the absorption and HRS assays. AuNP-DTNBA is able to detect Cr3+ at 20 ppb level at pH 6.0 using absorption spectral change of the AuNP-DTNBA. Visible color change can be observed when mixed with 250 ppb of Cr3+, while there is no color change when mixed with 2 ppm level of some of the most common metal ions such as Cr2O72-, Hg2+, Ba2+, Fe3+, Pb2+, Na+, Zn2+, Cd2+, Co2+, Mn2+, Ca2+, and Ni2+. However, a color change is observed when mixed with Ni2+, Zn2+, and Cd2+ at a concentration higher than 2 ppm. The detection limit for the HRS assay is on a remarkable 25 ppt level, and there is no detectable HRS signal at 2 ppm level for Cr2O72-, Hg2+, Ba2+, Fe3+, Pb2+, Na+, Zn2+, Cd2+, Co2+, Mn2+, Ca2+, and Ni2+.

Chloridodiphen-yl{[1-(1,3-thia-zol-2-yl-κN)ethyl-idene]-4-phenyl-thio-semicarbazidato-κN,S}tin(IV) methanol monosolvate.

The title compound, [Sn(C(6)H(5))(2)(C(12)H(11)N(4)S(2))Cl]·CH(4)O, is formed during the reaction between 2-acetyl-thia-zole 4-phenyl-thio-semicarbazone (Hacthptsc) and diphenyl-tin(IV) dichloride in methanol. In the crystal structure, the Sn atom exhibits an octa-hedral geometry with the [N(2)S] anionic tridentate thio-semicarbazone ligand having chloride trans to the central N and the two phenyl groups trans to each other. The Sn-Cl distance is 2.5929 (6), Sn-S is 2.4896 (6) and Sn-N to the central N is 2.3220 (16) Å. The MeOH mol-ecules link the Sn complexes into one-dimensional chains via N-H⋯O and O-H⋯Cl hydrogen bonds.

A label-free gold-nanoparticle-based SERS assay for direct cyanide detection at the parts-per-trillion level.

Cyanide is an extremely toxic lethal poison known to humankind. Developing rapid, highly sensitive, and selective detection of cyanide from water samples is extremely essential for human life safety. Driven by the need, here we report a gold-nanoparticle-based label-free surface-enhanced Raman spectroscopy (SERS) system for highly toxic cyanide ion recognition in parts-per-trillion level and to examine gold-nanoparticle-cyanide interaction. We have shown that the SERS assay can be used to probe the gold nanoparticle dissociation process in the presence of cyanide ions. Our experimental data indicates that gold-nanoparticle-based SERS can detect cyanide from a water sample at the 110 ppt level with excellent discrimination against other common anions and cations. The results also show that the SERS probe can be used to detect cyanide from environmental samples.

Iodido{4-phenyl-1-[1-(1,3-thia-zol-2-yl-κN)ethyl-idene]thio-semicarbazidato-κN',S}{4-phenyl-1-[1-(1,3-thia-zol-2-yl)ethyl-idene]thio-semicarbazide-κS}mercury(II).

In the title compound, [Hg(C(12)H(11)N(4)S(2))I(C(12)H(12)N(4)S(2))], the Hg atom is in a distorted square-pyramidal coordination, defined by the iodide ligand, by the S atom of the neutral ligand in the apical position, and by the N atom of the thia-zole ring, the thio-ureido N and the S atom of the deprotonated ligand. The deprotonated ligand intra-molecularly hydrogen bonds to the thia-zole ring N atom, while the deprotonated ligand forms an inter-molecular hydrogen bond to the thiol-ate S atom. The deprotonation of the tridentate ligand and its coordination to Hg via the S atom strikingly affects the C-S bond lengths. In the free ligand, the C-S bond distance is 1.685 (7) Å, whereas it is 1.749 (7) Šin the deprotonated ligand. Similarly, the Hg-S bond distance is slightly longer to the neutral ligand [2.6682 (18) Å] than to the deprotonated ligand [2.5202 (19) Å]. The Hg-I distance is 2.7505 (8) Å.

Photodegradation of selected PCBs in the presence of Nano-TiO2 as catalyst and H2O2 as an oxidant.

Photodegradation of five strategically selected PCBs was carried out in acetonitrile/water 80:20. Quantum chemical calculations reveal that PCBs without any chlorine on ortho-positions are closer to be planar, while PCBs with at least one chlorine atoms at the ortho-positions causes the two benzene rings to be nearly perpendicular. Light-induced degradation of planar PCBs is much slower than the perpendicular ones. The use of nano-TiO(2) speeds up the degradation of the planar PCBs, but slows down the degradation of the non-planar ones. The use of H(2)O(2) speeds up the degradation of planar PCBs greatly (by >20 times), but has little effect on non-planar ones except 2,3,5,6-TCB. The relative photodegradation rate is: 2,2',4,4'-TCB > 2,3,5,6-TCB > 2,6-DCB ≈ 3,3',4,4'-TCB > 3,4',5-TCB. The use of H(2)O(2) in combination with sunlight irradiation could be an efficient and "green" technology for PCB remediation.

Highly sensitive and selective dynamic light-scattering assay for TNT detection using p-ATP attached gold nanoparticle.

TNT is one of the most commonly used nitro aromatic explosives for landmines of military and terrorist activities. As a result, there is an urgent need for rapid and reliable methods for the detection of trace amount of TNT for screenings in airport, analysis of forensic samples, and environmental analysis. Driven by the need to detect trace amounts of TNT from environmental samples, this article demonstrates a label-free, highly selective, and ultrasensitive para-aminothiophenol (p-ATP) modified gold nanoparticle based dynamic light scattering (DLS) probe for TNT recognition in 100 pico molar (pM) level from ethanol:acetonitile mixture solution. Because of the formation of strong π-donor-acceptor interaction between TNT and p-ATP, para-aminothiophenol attached gold nanoparticles undergo aggregation in the presence of TNT, which changes the DLS intensity tremendously. A detailed mechanism for significant DLS intensity change has been discussed. Our experimental results show that TNT can be detected quickly and accurately without any dye tagging in 100 pM level with excellent discrimination against other nitro compounds.

Gold nanoparticle based label-free SERS probe for ultrasensitive and selective detection of trinitrotoluene.

TNT is one of the most commonly used nitro aromatic explosives used for landmine and military purpose. Due to the significant detrimental effects, contamination of soil and groundwater with TNT is the major concern. Driven by the need to detect trace amounts of TNT from environmental samples, this article demonstrates for the first time a highly selective and ultra sensitive, cysteine modified gold nanoparticle based label-free surface enhanced Raman spectroscopy (SERS) probe, for TNT recognition in 2 pico molar (pM) level in aqueous solution. Due to the formation of Meisenheimer complex between TNT and cysteine, gold nanoparticles undergo aggregation in the presence of TNT via electrostatic interaction between Meisenheimer complex bound gold nanoparticle and cysteine modified gold nanoparticle. As a result, it formed several hot spots and provided a significant enhancement of the Raman signal intensity by 9 orders of magnitude through electromagnetic field enhancements. A detailed mechanism for termendous SERS intensity change has been discussed. Our experimental results show that TNT can be detected quickly and accurately without any dye tagging in lower pM level with excellent discrimination against other nitro compounds and heavy metals.

Gold Nanoparticle Based Surface Enhanced Fluorescence For Detection of Organophosphorus Agents.

Organophosphorus agents (OPA) represent a serious concern to public safety as nerve agents and pesticides. Here we report the development of gold nanoparticle based surface enhanced fluorescence (NSEF) spectroscopy for rapid and sensitive screening of organophosphorus agents. Fluorescent from Eu3+ ions that are bound within the electromagnetic field of gold nanoparticles exhibit a strong enhancement. In the presence of OPA, Eu3+ ions are released from the gold nanoparticle surface and thus a very distinct fluorescence signal change was observed. We discussed the mechanism of fluorescence enhancement and the role of OPA for fluorescence intensity change in the presence of gold nanoparticles.