Kumbam Lingeshwar Reddy

Controlled synthesis, bioimaging and toxicity assessments in strong red emitting Mn2+ doped NaYF4:Yb3+/Ho3+ nanophosphors

Rare earth, Yb3+/Ho3+ doped NaYF4 nanophosphors showed augmentation of visible green and red light emission by the introduction of Mn2+ as a co-dopant. Nanophosphors were characterized for their morphology and upconversion (UC) fluorescence, as a function of co-dopant concentration. The effect of Mn2+ doping has been investigated to explore the UC mechanism of the phosphors. With the introduction of Mn2+, the intensity of all the emission bands was increased, in particular the red band, which was most significant at 40 mol% doping. A possible mechanism for the enhancement of the red emission has been proposed. The prepared UC nanoparticles were functionalized with polyethylene glycol–polyethylene imine co-polymer to make them water dispersible and successfully applied for cancer cell imaging.

Bioinspired Functional Surfaces for Technological Applications

Biological matters have been in continuous encounter with extreme environmental conditions leading to their evolution over millions of years. The fittest have survived through continuous evolution, an ongoing process. Biological surfaces are the important active interfaces between biological matters and the environment, and have been evolving over time to a higher state of intelligent functionality. Bioinspired surfaces with special functionalities have grabbed attention in materials research in the recent times. The microstructures and mechanisms behind these functional biological surfaces with interesting properties have inspired scientists to create artificial materials and surfaces which possess the properties equivalent to their counterparts. In this review, we have described the interplay between unique multiscale (micro- and nano-scale) structures of biological surfaces with intrinsic material properties which have inspired researchers to achieve the desired wettability and functionalities. Inspired by naturally occurring surfaces, researchers have designed and fabricated novel interfacial materials with versatile functionalities and wettability, such as superantiwetting surfaces (superhydrophobic and superoleophobic), omniphobic, switching wettability and water collecting surfaces. These strategies collectively enable functional surfaces to be utilized in different applications such as fog harvesting, surface-enhanced Raman spectroscopy (SERS), catalysis, sensing and biological applications. This paper delivers a critical review of such inspiring biological surfaces and artificial bioinspired surfaces utilized in different applications, where material science and engineering have merged by taking inspiration from the natural systems.

Selective and Sensitive Fluorescent Detection of Picric Acid by New Pyrene and Anthracene Based Copper Complexes

New pyrene and anthracene based copper complexes 4 and 7 respectively were designed, synthesized and characterized. The fluorescence behaviour of both 4 and 7 were evaluated towards nitro aromatics and anions. Both 4 and 7 possess high selectivity for the detection of well-known explosive picric acid (PA) by showing maximum fluorescence affinity. Furthermore, complex 4 showed similar sensing efficiency towards PA at different pH ranges. It was also used for real world applications, as illustrated by the very fast detection of PA from soil samples observed directly by naked eye.

Amorphous titania matrix impregnated with Ag nanoparticles as a highly efficient visible- and sunlight-active photocatalyst material

Abstract Amorphous titania matrix impregnated with Ag nanoparticles has been synthesised based on a facile colloidal synthesis route and has been explored for visible- and sunlight-activated photocatalytic applications. The photocatalytic activity of the material under visible light and sunlight irradiation was demonstrated by investigations on the degradation of a common pollutant, nitrobenzene. In comparison to other TiO2-based nanomaterials, this amorphous titania impregnated with Ag nanoparticles was found to be highly efficient for visible light as well as sunlight-active photocatalytic applications. The superior catalytic activity could be attributed to the efficient charge separation and lessened recombination of the photo-generated electrons and holes at the Ag–titania interface and the presence of multiple metal–metal oxide interfaces due to dispersed impregnation of Ag nanoparticles on amorphous titania matrix. Also, it was found that the photocatalytic activity of the prepared nanocomposites had better efficiency under the sunlight irradiation, which may be attributed to the plasmonic heating of the Ag nanoparticles in the sunlight. Fundamentally, this work illustrates that the dispersed impregnation of noble metal nanoparticles on semiconductor metal oxide matrix can be used to tune the photophysical properties of the final material to enhance its photocatalytic performance.

Rational Design and Development of Lanthanide-Doped NaYF4@CdS–Au–RGO as Quaternary Plasmonic Photocatalysts for Harnessing Visible–Near-Infrared Broadband Spectrum

Utilization of the total solar spectrum efficiently for photocatalysis has remained a huge challenge for a long time. However, designing a system by rationally combining nanocomponents with complementary properties, such as upconversion nanoparticles, semiconductors, plasmonic metals, and carbonaceous support, offers a promising route for efficient utilization of solar energy by harnessing the broadband spectrum. In this work, a series of novel quaternary plasmonic photocatalysts comprising of lanthanide-doped NaYF4@CdS (UC) core-shell nanostructures decorated with Au nanoparticles (Au NPs) supported on reduced graphene oxide (RGO) nanosheets were prepared using the multistep hydrothermal method. The different components of the prepared nanocomposites could be efficiently employed to utilize both the visible and near-infrared (NIR) regions. Specifically in this work, the utility of these quaternary nanocomposites for photocatalytic degradation of a colorless pharmaceutical pollutant, ciprofloxacin, under visible and NIR light irradiations has been demonstrated. In comparison to bare counterparts, our quaternary nanocomposites exhibit an enhanced photocatalytic activity attributable to the synergistic effect of different components arranged in such a way that favors harnessing energy from the broad spectral region and efficient charge separation. The combination of upconversion and plasmonic properties along with the advantages of a carbonaceous support can provide new physical insights for further development of photocatalysts, which could utilize the broadband spectrum.

Lanthanide Doped Near Infrared Active Upconversion Nanophosphors: Fundamental Concepts, Synthesis Strategies, and Technological Applications

Near infrared (NIR) light utilization in a range of current technologies has gained huge significance due to its abundance in nature and nondestructive properties. NIR active lanthanide (Ln) doped upconversion nanomaterials synthesized in controlled shape, size, and surface functionality can be combined with various pertinent materials for extensive applications in diverse fields. Upconversion nanophosphors (UCNP) possess unique abilities, such as deep tissue penetration, enhanced photostability, low toxicity, sharp emission peaks, long anti-Stokes shift, etc., which have bestowed them with prodigious advantages over other conventional luminescent materials. As new generation fluorophores, UCNP have found a wide range of applications in various fields. In this Review, a comprehensive overview of lanthanide doped NIR active UCNP is provided by discussing the fundamental concepts including the different mechanisms proposed for explaining the upconversion processes, followed by the different strategies employed for the synthesis of these materials, and finally the technological applications of UCNP, mainly in the fields of bioimaging, drug delivery, sensing, and photocatalysis by highlighting the recent works in these areas. In addition, a brief note on the applications of UCNP in other fields is also provided along with the summary and future perspectives of these materials.

Core-Shell Structures of Upconversion Nanocrystals Coated with Silica for Near Infrared Light Enabled Optical Imaging of Cancer Cells

Optical imaging of cancer cells using near infrared (NIR) light is currently an active area of research, as this spectral region directly corresponds to the therapeutic window of biological tissues. Upconversion nanocrystals are photostable alternatives to conventional fluorophores. In our work, we have prepared upconversion nanocrystals of NaYF4:Yb/Er and encapsulated them in silica to form core-shell structures. The as-prepared core-shell nanostructures have been characterized for their structure, morphology, and optical properties using X-ray diffraction, transmission electron microscopy coupled with elemental mapping, and upconversion luminescence spectroscopy, respectively. The cytotoxicity examined using cell viability assay indicated a low level of toxicity of these core-shell nanostructures. Finally, these core-shell nanostructures have been utilized as photostable probes for NIR light enabled optical imaging of human breast cancer cells. This work paves the way for the development of advanced photostable, biocompatible, low-toxic core-shell nanostructures for potential optical imaging of biological cells and tissues.

New Ni-Anthracene Complex for Selective and Sensitive Detection of 2,4,6-Trinitrophenol

Selective and sensitive detection of explosive materials through a simple approach is an attractive area of research having implications on public safety and homeland security. Considering this implication in mind, a new Ni-anthracene complex was designed and synthesized and has been demonstrated as an efficient fluorescence chemosensor for the selective and sensitive detection of 2,4,6-trinitrophenol. Firstly, a fluorescent anthracene ligand (A) was synthesized by treating anthracene-9-carboxaldehyde with 1,3-diaminopropane in presence of a weak acid. To achieve superior selectivity and great quenching efficiency for 2,4,6-trinitrophenol (TNP), a Ni complex, namely, [Ni( -L)(NO3)] (B), was synthesized via the reaction of A with Ni(NO3)2·6H2O. Complex B showed strong emission peak ( ) at 412 nm and exhibited high selectivity towards TNP among other nitroaromatics and anions. 100 equivalents of TNP made 95% fluorescence quenching of B and its detection limit for TNP was calculated as 2.8 μM.