Novel applications possibilities for phase-change materials and devices

Paper presented at European\Phase Change and Ovonics Symposium 2013, 2013-09-08, 2013-09-10, BerlinPhase-change materials and devices are most widely known for their use in optical and electrical non-volatile memory applications. Recently however the potential has been demonstrated for using phase-change materials and devices for a range of novel applications, including the provision of electronic 'mimics' of biological synapses and neurons (and their associated use in neuromorphic computing) and the provision of arithmetic and logic functionality. Furthermore, such neuromorphic, arithmetic and logic capabilities of phase-change materials and devices are accessible in both the optical (photonic) and the electrical (electronic) domains, or indeed via a 'mixed-mode' approach in which excitation is in the optical domain and detection is electrical, or vice-versa. This versatility of operation opens up the route towards various intriguing possibilities, such as 'all-optical' memory and computing devices, or the development of an optical analogue of the memristor, the so-called 'memflector'. In this paper we discuss such novel applications possibilities for phase-change materials and devices and present proof-of-principle of some of the underlying concepts

Two Dimensional Materials for Military Applications

This paper particularly focuses on 2D materials and their utilization in military applications. 2D and heterostructured 2D materials have great potential for military applications in developing energy storage devices, sensors, electronic devices, and weapon systems. Advanced 2D material-based sensors and detectors provide high awareness and significant opportunities to attain correct data required for planning, optimization, and decision-making, which are the main factors in the command and control processes in the military operations. High capacity sensors and detectors or energy storage can be developed not only by using 2D materials such as graphene, hexagonal boron nitride (hBN), MoS2, MoSe2, MXenes; but also by combining 2D materials to obtain heterostructures. Phototransistors, flexible thin-film transistors, IR detectors, electrodes for batteries, organic photovoltaic cells, and organic light-emitting diodes have been being developed from the 2D materials for devices that are used in weapon systems, chemical-biological warfare sensors, and detection systems. Therefore, the utilization of 2D materials is the key factor and the future of advanced sensors, weapon systems, and energy storage devices for military applications

“Green” Quantum Dots: Basics, Green Synthesis, and Nanotechnological Applications

Nanotechnological development of new materials involves the discovery or design of materials at small length scales with controlled physical and chemical properties than can be tuned or modified in function of their applications. One of the most suitable examples of nanoparticles used for this purpose are quantum dots, a type of colloidal fluorescent semiconducting nanocrystalline material that has the possibility, due to its unique optical and electronic properties, to be used in numerous technological applications such as biosensing, in vivo imaging techniques, photovoltaics, nanomedicine, molecular pathology, and drug delivery. Thus, there are almost endless possibilities for quantum dots materials. In spite of the fast advance in the search of quantum dots with better nanomaterial performance, environmentally benign and sustainable production is still lacking. Although the use of these materials is developing promptly, there is increasing concern that these materials might pose potential risks to human health. Herein, we discuss principal properties of quantum dots, including their functional architecture and toxicity, and review the main studies about “green” quantum dots synthesis to be aligned with green nanotechnology approach for nontoxic, cleaner, safer, and more responsible processes. The organometallic colloidal synthesis and the aqueous colloidal synthesis, as well as their drawbacks and benefits, are conferred. Recent advances in technological and biological quantum dots–based applications are also discussed in this chapter

Biohybrid plants with electronic roots via in vivo polymerization of conjugated oligomers

Plant processes, ranging from photosynthesis through production of biomaterials to environmental sensing and adaptation, can be used in technology via integration of functional materials and devices. Previously, plants with integrated organic electronic devices and circuits distributed in their vascular tissue and organs have been demonstrated. To circumvent biological barriers, and thereby access the internal tissue, plant cuttings were used, which resulted in biohybrids with limited lifetime and use. Here, we report intact plants with electronic functionality that continue to grow and develop enabling plant-biohybrid systems that fully maintain their biological processes. The biocatalytic machinery of the plant cell wall was leveraged to seamlessly integrate conductors with mixed ionic-electronic conductivity along the root system of the plants. Cell wall peroxidases catalyzed ETE-S polymerization while the plant tissue served as the template, organizing the polymer in a favorable manner. The conductivity of the resulting p(ETE-S) roots reached the order of 10 S cm(-1) and remained stable over the course of 4 weeks while the roots continued to grow. The p(ETE-S) roots were used to build supercapacitors that outperform previous plant-biohybrid charge storage demonstrations. Plants were not affected by the electronic functionalization but adapted to this new hybrid state by developing a more complex root system. Biohybrid plants with electronic roots pave the way for autonomous systems with potential applications in energy, sensing and robotics

Photoemission Electron Microscopy of Heterogeneous Two-Dimensional and Biological Materials

The engineering of nanoscale materials can fundamentally determine the macroscopic device functionalities for modern technologies. Similarly, there is also a hierarchy of length scales in nature that connects full-body biological activities with organ-level behavior, and eventually with molecular structures that are also on the nanometer scale. The design for high-performance and reproducible applications is constantly disturbed by structural heterogeneity such as edges, grain boundaries, and variations in domains and phases. The modified material morphology can lead to unique electronic states that impact the ultrafast dynamics of charge transfer or charge recombination. Structural variations are also ubiquitous in biological systems and they are critical to the functional forms of living systems. The knowledge of the structure-property relationship in both fields is highly demanded to achieve controlled, predictable functionalities of either device engineering or a biological body. In this thesis, we present our approaches to entangling the nanoscale heterogeneous information using a novel technique, photoemission electron microscopy, or PEEM. In particular, we will focus on the study of two-dimensional materials and neurological tissues with several variations of PEEM configurations. Chapter 1 introduces the motivations for this thesis, explains the necessary theory background on photoemission and electron imaging, exemplifies PEEM applications that are closely related to this thesis, and provides a summary of the system of study, including 2D black phosphorus, a perylene diimide (PDI)/MoS2 bilayer heterostructure, and ultra-thin mouse brain sections. Chapter 2 describes the details of the experimental apparatus constructed to realize the research goal. We will cover an ultrafast laser as well as two distinct PEEM systems, and explain the setups for polarization-dependent and time-resolved PEEM experiments. Chapter 3 discusses current progress and challenges for preparing and characterizing mechanically exfoliated 2D materials. Chapter 4 details the study of edge-specific characteristics of 2D black phosphorus using polarization-dependent PEEM. Chapter 5 discusses a time-resolved PEEM study on the nanoscale ultrafast dynamics of PDI/MoS2 bilayer heterostructures. Chapter 6 introduces the applications of PEEM to neuroscience and demonstrates the potential for fast 3D imaging as well as the contrast mechanism of osmium-stained biological tissues. Chapter 7 extends the previous discussion and presents a few ongoing experiments that open the opportunities of PEEM to wider applications

Can Carbon Nanotubes Deliver on their Promise in Biology? Harnessing Unique Properties for Unparalleled Applications

Carbon nanotubes (CNTs) are cylindrical sheets of hexagonally ordered carbon atoms, giving tubes with diameters on the order of a few nanometers and lengths typically in the micrometer range. They may be single- or multiwalled (SWCNTs and MWCNTs respectively). Since the seminal report of their synthesis in 1991, CNTs have fascinated scientists of all stripes. Physicists have been intrigued by their electrical, thermal, and vibrational potential. Materials scientists have worked on integrating them into ultrastrong composites and electronic devices, while chemists have been fascinated by the effects of curvature on reactivity and have developed new synthesis and purification techniques. However, to date no large-scale, real-life biotechnological CNT breakthrough has been industrially adopted and it is proving difficult to justify taking these materials forward into the clinic. We believe that these challenges are not the end of the story, but that a viable carbon nanotube biotechnology is one in which the unique properties of nanotubes bring about an effect that would be otherwise impossible. In this Outlook, we therefore seek to reframe the field by highlighting those biological applications in which the singular properties of CNTs provide some entirely new activity or biological effect as a pointer to "what could be"

Evaluation of the Structure-Activity Relationship of Hemoproteins through Physicochemical Studies: Hemoglobins as a Prototype of Biosensor

In the present work, we have studied a group of prerequisites in terms of “structure-function relationship” of hemoproteins, especially hemoglobins, emphasizing the role of the heme and its chemical environment in the biochemical and physicochemical properties of the biomolecule. We have discussed the ferrous center and its properties as coordination center; the macrocyclic ligands, especially the porphyrins; the esterochemical and electronic properties of the iron-porphyrins (heme groups); and the interaction between heme groups and globins, which is related to several redox and oligomeric properties of hemoprotein systems and its potential applications with respect to novel materials. One of the main uses of hemoglobins in new materials is also discussed, which is its employment as a biosensor. Therefore, we have discussed the development of novel biosensors based on hemoglobins and their physico-chemical properties as well as on the main molecules of biological relevance that have been detected by these biosensors, such as hydrogen peroxide (H2O2), nitric oxide (NO), and cholesterol, among others. Indeed, several important biomolecules and biological processes can be detected and/or evaluated by devices that present hemoglobins as leading chemical components. Different apparatus are covered with respect to distinct characteristics, such as chemical stability, sensitivity, selectivity, reproducibility, durability, optimum conditions of measurements, etc. and their respective characteristics are analyzed