Sirimuvva Tadepalli

Bilayered Biofoam for Highly Efficient Solar Steam Generation.

A novel bilayered hybrid biofoam composed of a bacterial nanocellulose (BNC) layer and a reduced graphene oxide (RGO)-filled BNC layer is introduced for highly efficient solar steam generation. The biofoam exhibits a solar thermal efficiency of ≈83% under simulated solar illumination (10 kW m-2 ). The fabrication method introduced here is highly scalable and cost-efficient.

Wood–Graphene Oxide Composite for Highly Efficient Solar Steam Generation and Desalination

Solar steam generation is a highly promising technology for harvesting solar energy, desalination and water purification. We introduce a novel bilayered structure composed of wood and graphene oxide (GO) for highly efficient solar steam generation. The GO layer deposited on the microporous wood provides broad optical absorption and high photothermal conversion resulting in rapid increase in the temperature at the liquid surface. On the other hand, wood serves as a thermal insulator to confine the photothermal heat to the evaporative surface and to facilitate the efficient transport of water from the bulk to the photothermally active space. Owing to the tailored bilayer structure and the optimal thermo-optical properties of the individual components, the wood-GO composite structure exhibited a solar thermal efficiency of ∼83% under simulated solar excitation at a power density of 12 kW/m2. The novel composite structure demonstrated here is highly scalable and cost-efficient, making it an attractive material for various applications involving large light absorption, photothermal conversion and heat localization.

Plasmonic Biofoam: A Versatile Optically Active Material

Owing to their ability to confine and manipulate light at the nanoscale, plasmonic nanostructures are highly attractive for a broad range of applications. While tremendous progress has been made in the synthesis of size- and shape-controlled plasmonic nanostructures, their integration with other materials and application in solid-state is primarily through their assembly on rigid two-dimensional (2D) substrates, which limits the plasmonically active space to a few nanometers above the substrate. In this work, we demonstrate a simple method to create plasmonically active three-dimensional biofoams by integrating plasmonic nanostructures with highly porous biomaterial aerogels. We demonstrate that plasmonic biofoam is a versatile optically active platform that can be harnessed for numerous applications including (i) ultrasensitive chemical detection using surface-enhanced Raman scattering; (ii) highly efficient energy harvesting and steam generation through plasmonic photothermal heating; and (iii) optical control of enzymatic activity by triggered release of biomolecules encapsulated within the aerogel. Our results demonstrate that 3D plasmonic biofoam exhibits significantly higher sensing, photothermal, and loading efficiency compared to conventional 2D counterparts. The design principles and processing methodology of plasmonic aerogels demonstrated here can be broadly applied in the fabrication of other functional foams.

Multifunctional Hybrid Nanopatches of Graphene Oxide and Gold Nanostars for Ultraefficient Photothermal Cancer Therapy

Multifunctional hybrid nanomaterials with enhanced therapeutic efficiency at physiologically safe dosages for externally triggered, image-guided therapy are highly attractive for nanomedicine. Here, we demonstrate a novel class of multifunctional hybrid nanopatches comprised of graphene oxide (GO) and gold nanostars for enhanced photothermal effect and image-guided therapy. The hybrid nanopatches with tunable localized surface plasmon resonance into the near-infrared therapeutic window (650-900 nm) were realized using a biofriendly method that obviates the need for toxic shape-directing agents. Internalization of the intact nanopatches into epithelial breast cancer cells was confirmed by Raman imaging, transmission electron microscopy, and inductively coupled plasma mass spectrometry. It appears that the amphipathic nature and the large surface area of the graphene oxide enable it to serve as a soft, flexible, and biocompatible intracellular carrier for the in situ grown plasmonic nanostructures and provide long-term biocompatibility with extremely low cytotoxicity. Apart from a remarkably improved photothermal effect compared to that of either of the components at very low dosages of the hybrids (10 μg/mL GO) and using a low laser power (0.75 W cm(-2)), the hybrid nanopatches exhibit strong Raman scattering, making them excellent candidates for bioimaging, diagnostics, and image-guided therapy applications.

Plasmonic nanorattles with intrinsic electromagnetic hot-spots for surface enhanced Raman scattering.

The synthesis of plasmonic nanorattles with accessible electromagnetic hotspots that facilitate highly sensitive detection of chemical analytes using surface enhanced Raman scattering (SERS) is demonstrated. Raman spectra obtained from individual nanorattles demonstrate the significantly higher SERS activity compared to solid plasmonic nanostructures.

Hydrophilic, bactericidal nanoheater-enabled reverse osmosis membranes to improve fouling resistance.

Polyamide (PA) semipermeable membranes typically used for reverse osmosis water treatment processes are prone to fouling, which reduces the amount and quality of water produced. By synergistically coupling the photothermal and bactericidal properties of graphene oxide (GO) nanosheets, gold nanostars (AuNS), and hydrophilic polyethylene glycol (PEG) on PA reverse osmosis membrane surfaces, we have dramatically improved fouling resistance of these membranes. Batch fouling experiments from three classes of fouling are presented: mineral scaling (CaCO3 and CaSO4), organic fouling (humic acid), and biofouling (Escherichia coli). Systematic analyses and a variety of complementary techniques were used to elucidate fouling resistance mechanisms from each layer of modification on the membrane surface. Both mineral scaling and organic fouling were significantly reduced in PA-GO-AuNS-PEG membranes compared to other membranes. The PA-GO-AuNS-PEG membrane was also effective in killing all near-surface bacteria compared to PA membranes. In the PA-GO-AuNS-PEG membrane, the GO nanosheets act as templates for in situ AuNS growth, which then facilitated localized heating upon irradiation by an 808 nm laser inactivating bacteria on the membrane surface. Furthermore, AuNS in the membrane assisted PEG in preventing mineral scaling on the membrane surface. In flow-through flux and foulant rejection tests, PA-GO-AuNS-PEG membranes performed better than PA membranes in the presence of CaSO4 and humic acid model foulants. Therefore, the newly suggested membrane surface modifications will not only reduce fouling from RO feeds, but can improve overall membrane performance. Our innovative membrane design reported in this study can significantly extend the lifetime and water treatment efficacy of reverse osmosis membranes to alleviate escalating global water shortage from rising energy demands.

Bio-Optics and Bio-Inspired Optical Materials

Through the use of the limited materials palette, optimally designed micro- and nanostructures, and tightly regulated processes, nature demonstrates exquisite control of light-matter interactions at various length scales. In fact, control of light-matter interactions is an important element in the evolutionary arms race and has led to highly engineered optical materials and systems. In this review, we present a detailed summary of various optical effects found in nature with a particular emphasis on the materials and optical design aspects responsible for their optical functionality. Using several representative examples, we discuss various optical phenomena, including absorption and transparency, diffraction, interference, reflection and antireflection, scattering, light harvesting, wave guiding and lensing, camouflage, and bioluminescence, that are responsible for the unique optical properties of materials and structures found in nature and biology. Great strides in understanding the design principles adapted by nature have led to a tremendous progress in realizing biomimetic and bioinspired optical materials and photonic devices. We discuss the various micro- and nanofabrication techniques that have been employed for realizing advanced biomimetic optical structures.

Bioplasmonic calligraphy for multiplexed label-free biodetection

Printable multi-marker biochips that enable simultaneous quantitative detection of multiple target biomarkers in point-of-care and resource-limited settings are a holy grail in the field of biodiagnostics. However, preserving the functionality of biomolecules, which are routinely employed as recognition elements, during conventional printing approaches remains challenging. In this article, we introduce a simple yet powerful approach, namely plasmonic calligraphy, for realizing multiplexed label-free bioassays. Plasmonic calligraphy involves a regular ballpoint pen filled with biofunctionalized gold nanorods as plasmonic ink for creating isolated test domains on paper substrates. Biofriendly plasmonic calligraphy approach serves as a facile method to miniaturize the test domain size to few mm(2), which significantly improves the sensitivity of the plasmonic biosensor compared to bioplasmonic paper fabricated using immersion approach. Furthermore, plasmonic calligraphy also serves as a simple and efficient means to isolate multiple test domains on a single test strip, which facilitates multiplexed biodetection and multi-marker biochips. Plasmonic calligraphy, which can be potentially automated by implementing with a robotic arm, serves as an alternate path forward to overcome the limitations of conventional ink-jet printing.

Multiplexed charge-selective surface enhanced Raman scattering based on plasmonic calligraphy

Multiplexed surface enhanced Raman scattering (SERS) substrates, which enable chemically selective detection of two or more target analytes from a complex chemical mixture, are highly attractive for chemical detection in real-world settings. We introduce a new approach called plasmonic calligraphy that involves the formation of chemically selective test domains on paper substrates using functionalized plasmonic nanostructures as ink in a regular ballpoint pen. We demonstrate selective detection of positively and negatively charged analytes (rhodamine 6G and methyl orange) from complex chemical mixtures using polyelectrolyte-coated gold nanorods as SERS medium. The approach demonstrated here obviates the need for complex patterning techniques such as photolithography to create isolated test domains on paper substrates for multiplexed chemical detection. Plasmonic calligraphy can be easily extended to other shape-controlled nanostructures with different surface functionalities and potentially automated by implementation with a robotic arm.

Bio‐Enabled Gold Superstructures with Built‐In and Accessible Electromagnetic Hotspots

The bio-enabled synthesis of a novel class of surface enhanced Raman scattering probes is presented for functional imaging with built-in and accessible electromagnetic hotspots formed between densely packed satellites grown on a plasmonic core. The superstructures serve as nanoscale sensors to spatiotemporally map intravesicular pH changes along endocytic pathways inside live cells.