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Fluorescence imaging is a powerful tool for studying biologically relevant macromolecules, but its applicability is often limited by the fluorescent probe, which must demonstrate both high site‐specificity and emission efficiency. In this regard, M13 virus, a versatile biological scaffold, has previously been used to both assemble fluorophores on its viral capsid with molecular precision and to also target a variety of cells. Although M13‐fluorophore systems are highly selective, these complexes typically suffer from poor molecular detection limits due to low absorption cross‐sections and moderate quantum yields. To overcome these challenges, a coassembly of the M13 virus, cyanine 3 dye, and silver nanoparticles is developed to create a fluorescent tag capable of binding with molecular precision with high emissivity. Enhanced emission of cyanine 3 of up to 24‐fold is achieved by varying nanoparticle size and particle‐fluorophore separation. In addition, it is found that the fluorescence enhancement increases with increasing dye surface density on the viral capsid. Finally, this highly fluorescent probe is applied for in vitro staining of E. coli . These results demonstrate an inexpensive framework for achieving tuned fluorescence enhancements. The methodology developed in this work is potentially amendable to fluorescent detection of a wide range of M13/cell combinations., Defense Advanced Research Projects Agency (Award HR0011-15-C-0084)

Detection of biological features at the cellular level with sufcient sensitivity in complex tissue remains a major challenge. To appreciate this challenge, this would require fnding tens to hundreds of cells (a 0.1 mm tumor has ~125 cells), out of ~37 trillion cells in the human body. Near-infrared optical imaging holds promise for high-resolution, deep-tissue imaging, but is limited by autofuorescence and scattering. To date, the maximum reported depth using second-window near-infrared (NIR-II: 1000–1700 nm) fuorophores is 3.2 cm through tissue. Here, we design an NIR-II imaging system, “Detection of Optically Luminescent Probes using Hyperspectral and difuse Imaging in Near-infrared” (DOLPHIN), that resolves these challenges. DOLPHIN achieves the following: (i) resolution of probes through up to 8 cm of tissue phantom; (ii) identifcation of spectral and scattering signatures of tissues without a priori knowledge of background or autofuorescence; and (iii) 3D reconstruction of live whole animals. Notably, we demonstrate noninvasive real-time tracking of a 0.1 mm-sized fuorophore through the gastrointestinal tract of a living mouse, which is beyond the detection limit of current imaging modalities., Untied States. National Cancer Institute. Cancer Center Support (Grant P30-CA14051), United States. National Cancer Institute. Center for Cancer Nanotechnology Excellence (Grant 5-U54-CA151884-03)

We present herein an experimental screening study that assesses how partially replacing Pb in methylammonium lead triiodide perovskite films with nine different alternative, divalent metal species, B = {Co, Cu, Fe, Mg, Mn, Ni, Sn, Sr, and Zn}, influences photovoltaic performance and optical properties. Our findings indicate the perovskite film is tolerant to most of the considered homovalent metal species with lead-cobalt compositions yielding the highest power conversion efficiencies when less than 6% of the Pb2+ ions are replaced. Through subsequent materials characterisation, we demonstrate for the first time that partially substituting Pb2+ at the B-sites of the perovskite lattice is not restricted to Group IV elements but is also possible with at least Co2+. Moreover, adjusting the molar ratio of Pb: Co in the mixed-metal perovskite affords new opportunities to tailor the material properties while maintaining stabilised device efficiencies above 16% in optimised solar cells. Specifically, crystallographic analysis reveals that Co2+ incorporates into the perovskite lattice and increasing its concentration can mediate a crystal structure transition from the cubic to tetragonal phase at room-temperature. Likewise, Co2+ substitution continually modifies the perovskite work function and band edge energies without either changing the band gap or electronically doping the intrinsic material. By leveraging this orthogonal dimension of electronic tunability, we achieve remarkably high open-circuit voltages up to 1.08 V with an inverted device architecture by shifting the perovskite into a more favourable energetic alignment with the PEDOT: PSS hole transport material., Funding Agencies|Eni, S. p. A. (Italy) through the MIT Energy Initiative Program; People Programme (Marie Curie Actions) of the European Unions Seventh Framework Programme under REA [PIOF-GA-2013-622630]; Fannie and John Hertz Foundation; National Science Foundation

Fluorescence imaging in the second near-infrared window (NIR-II, 1,000–1,700 nm) features deep tissue penetration, reduced tissue scattering, and diminishing tissue autofluorescence. Here, NIR-II fluorescent probes, including down-conversion nanoparticles, quantum dots, single-walled carbon nanotubes, and organic dyes, are constructed into biocompatible nanoparticles using the layer-by-layer (LbL) platform due to its modular and versatile nature. The LbL platform has previously been demonstrated to enable incorporation of diagnostic agents, drugs, and nucleic acids such as siRNA while providing enhanced blood plasma half-life and tumor targeting. This work carries out head-to-head comparisons of currently available NIR-II probes with identical LbL coatings with regard to their biodistribution, pharmacokinetics, and toxicities. Overall, rare-earth-based down-conversion nanoparticles demonstrate optimal biological and optical performance and are evaluated as a diagnostic probe for high-grade serous ovarian cancer, typically diagnosed at late stage. Successful detection of orthotopic ovarian tumors is achieved by in vivo NIR-II imaging and confirmed by ex vivo microscopic imaging. Collectively, these results indicate that LbL-based NIR-II probes can serve as a promising theranostic platform to effectively and noninvasively monitor the progression and treatment of serous ovarian cancer., United States. Department of Defense. Ovarian Cancer Research Program (TEAL Innovator Award OC120504), National Cancer Institute (U.S.) (Center for Cancer Nanotechnology Excellence Grant 5-U54- CA151884-03)

Mesoporous semiconducting networks exhibit advantageous photoelectrochemical properties. The M13 virus is a versatile biological scaffold that has been genetically engineered to organize various materials into nanowire (NW)-based mesoporous structures. In this study, high-aspect ratio titanium dioxide NWs are synthesized by utilizing M13 viruses as templates, and the NWs are assembled into semiconducting mesoporous networks with tunable structural properties. To understand the effects of different morphologies on the photovoltaic performance, the as-fabricated networks are employed as photoanodes in liquid-state dye-sensitized solar cells (DSCs). Compared with traditional nanoparticle-based photoanodes, the NW-based DSC photoanodes demonstrate much higher electron diffusion lengths while maintaining a comparable light harvesting capacity, thus leading to improved power conversion efficiencies. In addition, the NW-based semiconducting mesoporous thin films are able to load sufficient organolead iodide perovskite materials into the interconnected pores, and the perovskite-coated films are utilized as efficient photoanodes for solid-state organolead iodide perovskite hybrid solar cells and achieve power conversion efficiencies superior to those of liquid-state DSCs., Eni S.p.A. (Firm) (Eni-MIT Energy Fellowship), Natural Sciences and Engineering Research Council of Canada (Postgraduate Scholarship)

Utilization of the material-specific peptide–substrate interactions of M13 virus broadens colloidal stability window of graphene. The homogeneous distribution of graphene is maintained in weak acids and increased ionic strengths by complexing with virus. This graphene/virus conducting template is utilized in the synthesis of energy-storage materials to increase the conductivity of the composite electrode. Successful formation of the hybrid biological template is demonstrated by the mineralization of bismuth oxyfluoride as a cathode material for lithium-ion batteries, with increased loading and improved electronic conductivity., National Institute for International Education (Korea) (Korean Government Scholarship Program), United States. Army Research Office (Institute for Collaborative Biotechnologies (ICB)), National Institutes of Health (U.S.) (Materials Research Science and Engineering Centers program)

In photovoltaic devices, light harvesting (LH) and carrier collection have opposite relations with the thickness of the photoactive layer, which imposes a fundamental compromise for the power conversion efficiency (PCE). Unbalanced LH at different wavelengths further reduces the achievable PCE. Here, we report a novel approach to broadband balanced LH and panchromatic solar energy conversion using multiple-core–shell structured oxide-metal-oxide plasmonic nanoparticles. These nanoparticles feature tunable localized surface plasmon resonance frequencies and the required thermal stability during device fabrication. By simply blending the plasmonic nanoparticles with available photoactive materials, the broadband LH of practical photovoltaic devices can be significantly enhanced. We demonstrate a panchromatic dye-sensitized solar cell with an increased PCE from 8.3% to 10.8%, mainly through plasmon-enhanced photoabsorption in the otherwise less harvested region of solar spectrum. This general and simple strategy also highlights easy fabrication, and may benefit solar cells using other photoabsorbers or other types of solar-harvesting devices., Eni-MIT Energy Initiative Founding Member Program, National Science Foundation (U.S.) (ECCS Award 1028568), United States. Air Force Office of Scientific Research (AFOSR MURI Award FA9550-12-1-0488)

By genetically encoding affinity for inorganic materials into the capsid proteins of the M13 bacteriophage, the virus can act as a template for the synthesis of nanomaterial composites for use in various device applications. Herein, the M13 bacteriophage is employed to build a multifunctional and three-dimensional scaffold capable of improving both electron collection and light harvesting in dye-sensitized solar cells (DSSCs). This has been accomplished by binding gold nanoparticles (AuNPs) to the virus proteins and encapsulating the AuNP–virus complexes in TiO2 to produce a plasmon-enhanced and nanowire (NW)-based photoanode. The NW morphology exhibits an improved electron diffusion length compared to traditional nanoparticle-based DSSCs, and the AuNPs increase the light absorption of the dye-molecules through the phenomenon of localized surface plasmon resonance. Consequently, we report a virus-templated and plasmon-enhanced DSSC with an efficiency of 8.46%, which is achieved through optimizing both the NW morphology and the concentration of AuNPs loaded into the solar cells. In addition, we propose a theoretical model that predicts the experimentally observed trends of plasmon enhancement., National Science Foundation (U.S.) (award number DMR- 0819762), MIT Energy Initiative (Eni-MIT Energy Fellowship), United States. Air Force Office of Scientific Research (AFOSR MURI Award No. FA9550-12-1-0488), National Science Foundation (U.S.) (ECCS Award No. 1028568), Eni S.p.A. (Firm)

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student-submitted PDF version of thesis., Includes bibliographical references (p. 206-217)., Lack of energy supply and non-uniform distribution of traditional energy sources, such as coal, oil, and natural gas, have brought up tremendous social issues. To solve these issues, highly efficient energy conversion devices including solar cells, water splitting cells, and lithium-ion batteries are required. In this thesis, by utilizing the biological scaffolds of M13 bacteriophage, nanocomposites with novel nanostructures and various functional nanomaterials have been synthesized, assembled, and fabricated into devices. Using excellent properties from each functional material in the nanocomposites, performance of the energy conversion devices has been improved. Specifically, in dye-sensitized solar cells, the electron collection efficiency is improved by the complex of the viruses and single-walled carbon nanotubes. The light harvesting efficiency is also improved by localized surface plasmon-enhanced photo-absorption of dye-molecules, with and without adding viruses into the titania photoanodes of dye-sensitized solar cells. In addition, virus-graphene complex is utilized to enhance the performance of lithium-ion batteries, by increasing the electron conductivity throughout the cathode active materials. Moreover, two types of virus-templated perovskite ternary metal oxide materials (strontium titanate and bismuth ferrite) are synthesized and demonstrated for photocatalytic and photovoltaic properties., by Xiangnan Dang., Ph.D.

Single-layer graphene sheets have significantly broadened the horizon of nanotechnology with the unique electronic, optical, quantum mechanical and mechanical properties associated with the two-dimensional atomic crystal structure. To best utilize this material for practical applications, it is crucial to prevent the spontaneous aggregation between individual graphene sheets while composite materials are formed. Numerous efforts have been made to stabilize functionalized graphene sheets on molecular[2] or polymeric species. Biomolecules such as DNA and proteins have also been grafted onto graphene planes and used for biosensors, controlled drug-delivery as well as cancer imaging. As well as biomedical applications, graphene sheets can also be hybridized with biomolecules into energy-storage devices to increase the conductivity of the active materials that are often insulators. In previous work, ultrasonication or chemical reduction, followed by heat treatment, have been adopted to achieve composites between graphene and various materials (e.g., LiFePO4 and SnO2. However, due to the non-specific nature of the interactions between the graphene templates and active materials, it is expected that only random and inhomogeneous contacts are created, leaving the segregation on nano- or even sub-micrometer levels., Published in the Journal of Small, v8 n7 p1006-1011, 2012.