Nanotechnology for more efficient photovoltaics: the quantum dot intermediate band solar cell

The intermediate band solar cell [1] has been proposed as a concept able to substantially enhance the efficiency limit of an ordinary single junction solar cell. If a band permitted for electrons is inserted within the forbidden band of a semiconductor then a novel path for photo generation is open: electron hole pairs may be formed by the successive absorption of two sub band gap photons using the intermediate band (IB) as a stepping stone. While the increase of the photovoltaic (PV) current is not a big achievement —it suffices to reduce the band gap— the achievement of this extra current at high voltage is the key of the IB concept. In ordinary cells the voltage is limited by the band gap so that reducing it would also reduce the band gap. In the intermediate band solar cell the high voltage is produced when the IB is permitted to have a Quasi Fermi Level (QFL) different from those of the Conduction Band (CB) and the Valence Band (VB). For it the cell must be properly isolated from the external contacts, which is achieved by putting the IB material between two n- and p-type ordinary semiconductors [2]. Efficiency thermodynamic limit of 63% is obtained for the IB solar cell1 vs. the 40% obtained [3] for ordinary single junction solar cells. Detailed information about the IB solar cells can be found elsewhere [4].

Nanotechnology for high frequency communications: nitrides and graphene

The achievement of higher frequencies (HF) and the reduction of energy consumption, to improve sensing, communication and computation, involve the continued scaling down to the nanometer level. This scaling is enabled by of innovative device designs, improved processing technologies and assessment tools, and new material structures. In this work, we have used all these factors to demonstrate state-of-the-art HF devices in two materials with quite different electronic properties: wide semiconductor bandgap III-nitrides for resonators and power amplifiers; and graphene, a zero bandgap material expected to revolutionize low noise and HF flexible electronics. Some issues faced during their development will be discussed during the talk.

Bottom-up risk regulation? How nanotechnology risk knowledge gaps challenge federal and state environmental agencies

Nanotechnologies have been called the "Next Industrial Revolution." At the same time, scientists are raising concerns about the potential health and environmental risks related to the nano-sized materials used in nanotechnologies. Analyses suggest that current U.S. federal regulatory structures are not likely to adequately address these risks in a proactive manner. Given these trends, the premise of this paper is that state and local-level agencies will likely deal with many "end-of-pipe" issues as nanomaterials enter environmental media without prior toxicity testing, federal standards, or emissions controls. In this paper we (1) briefly describe potential environmental risks and benefits related to emerging nanotechnologies; (2) outline the capacities of the Toxic Substances Control Act, the Clean Air Act, the Clean Water Act, and the Resources Conservation and Recovery Act to address potential nanotechnology risks, and how risk data gaps challenge these regulations; (3) outline some of the key data gaps that challenge state-level regulatory capacities to address nanotechnologies' potential risks, using Wisconsin as a case study; and (4) discuss advantages and disadvantages of state versus federal approaches to nanotechnology risk regulation. In summary, we suggest some ways government agencies can be better prepared to address nanotechnology risk knowledge gaps and risk management.

Nanotechnology for the delivery of vaccines

Liposomes offer an ideal platform for the delivery of subunit vaccines, due to their versatility and flexibility, which allows for antigen as well as immunostimulatory lipids and TLR agonists to become associated with these bilayered vesicles. Liposomes have the ability to protect vaccine antigen, as well as enhance delivery to antigen presenting cells, whilst the importance of cationic surface charge for delivery of TB subunit vaccines and formation of an ‘antigen depot’ may play a key role in boosting cell-mediated immunity and Th1 immune responses. The rational design of vaccine adjuvants requires the thorough investigation into the physicochemical characteristics that dictate the function of a liposomal adjuvant. Within this thesis, physicochemical characteristics were investigated in order to show any effects on the biodistribution profiles and the ensuing immune responses of these formulations. Initially the role of liposome charge within the formulation was investigated and subsequently their efficacy as vaccine adjuvants in combination with their biodistribution was measured to allow the role of formulation in vaccine function to be considered. These results showed that cationic surface charge, in combination with high loading of H56 vaccine antigen through electrostatic binding, was crucial in the promotion of the ‘depot-effect’ at the injection site which increases the initiation of Th1 cell-mediated immune responses that are required to offer protection against tuberculosis. To further investigate this, different methods of liposome production were also investigated where antigen incorporation within the vesicles as well as surface adsorption were adopted. Using the dehydration-rehydration (DRV) method (where liposomes are freeze-dried in the presence of antigen to promote antigen encapsulation) and the double emulsion (DE) method, a range of liposomes entrapping antigen were formulated. Variation in the liposome preparation method can lead to antigen entrapment within the delivery system which has been shown to be greater for DRV-formulated liposomes compared to their DE-counterparts. This resulted in no significant effect on the vaccine biodistribution profile, as well as not significantly altering the efficacy of cationic liposomal adjuvants. To further enhance the efficacy of these systems, the addition of TLR agonists either at the vesicle surface as well as within the delivery system has been displayed through variation in the preparation method. Anionic liposomal adjuvants have been formulated, which displayed rapid drainage from the injection site to the draining lymph nodes and displayed a reduction in measured Th1 immune responses. However, variation in the preparation method can alter the immune response profile for anionic liposomal adjuvants with a bias in immune response to Th2 responses being noted. Through the use of high shear mixing and stepwise incorporation, the efficient loading of TLR agonist within liposomes has been shown. However, interestingly the conjugation between lipid and non-electrostatically bound TLR agonist, followed by insertion into the bilayer of DDA/TDB resulted in localised agonist retention at the injection site and further stimulation of the Th1 immune response at the SOI, spleen and draining lymphatics as well as enhanced antibody titres.

Responsive brushes and gels as components of soft nanotechnology

Progress in the development of generic molecular devices based on responsive polymers is discussed. Characterisation of specially synthesised polyelectrolyte gels, "grafted from" brushes and triblock copolymers is reported. A Landolt pH-oscillator, based on bromate/ sulfite/ferrocyanide, with a room temperature period of 20 min and a range of 3.1

Nanotechnology and microfluidics:formulation design and on-chip manufacture of nanoparticles

Nanoparticles offer an ideal platform for the delivery of small molecule drugs, subunit vaccines and genetic constructs. Besides the necessity of a homogenous size distribution, defined loading efficiencies and reasonable production and development costs, one of the major bottlenecks in translating nanoparticles into clinical application is the need for rapid, robust and reproducible development techniques. Within this thesis, microfluidic methods were investigated for the manufacturing, drug or protein loading and purification of pharmaceutically relevant nanoparticles. Initially, methods to prepare small liposomes were evaluated and compared to a microfluidics-directed nanoprecipitation method. To support the implementation of statistical process control, design of experiment models aided the process robustness and validation for the methods investigated and gave an initial overview of the size ranges obtainable in each method whilst evaluating advantages and disadvantages of each method. The lab-on-a-chip system resulted in a high-throughput vesicle manufacturing, enabling a rapid process and a high degree of process control. To further investigate this method, cationic low transition temperature lipids, cationic bola-amphiphiles with delocalized charge centers, neutral lipids and polymers were used in the microfluidics-directed nanoprecipitation method to formulate vesicles. Whereas the total flow rate (TFR) and the ratio of solvent to aqueous stream (flow rate ratio, FRR) was shown to be influential for controlling the vesicle size in high transition temperature lipids, the factor FRR was found the most influential factor controlling the size of vesicles consisting of low transition temperature lipids and polymer-based nanoparticles. The biological activity of the resulting constructs was confirmed by an invitro transfection of pDNA constructs using cationic nanoprecipitated vesicles. Design of experiments and multivariate data analysis revealed the mathematical relationship and significance of the factors TFR and FRR in the microfluidics process to the liposome size, polydispersity and transfection efficiency. Multivariate tools were used to cluster and predict specific in-vivo immune responses dependent on key liposome adjuvant characteristics upon delivery a tuberculosis antigen in a vaccine candidate. The addition of a low solubility model drug (propofol) in the nanoprecipitation method resulted in a significantly higher solubilisation of the drug within the liposomal bilayer, compared to the control method. The microfluidics method underwent scale-up work by increasing the channel diameter and parallelisation of the mixers in a planar way, resulting in an overall 40-fold increase in throughput. Furthermore, microfluidic tools were developed based on a microfluidics-directed tangential flow filtration, which allowed for a continuous manufacturing, purification and concentration of liposomal drug products.

Defining Key Inventors: A Comparison of Fuel Cell and Nanotechnology Industries

This paper defines the notion of key inventors — those whose patenting is simultaneously highly productive and also widely cited. By implication, key inventors should be the leaders in any developing new field and we investigate the validity of the notion through an exploration of two emerging technological fields: fuel cell and nanotechnology. The nature of the two groups is compared to discuss the differences between the technological groups.

Nanotechnology in the food industry I: applications

Nanotechnology is a multidisciplinary science that is having a boom today, providing new products with attractive physicochemical properties for many applications. In agri/feed/food sector, nanotechnology offers great opportunities for obtaining products and innovative applications for agriculture and livestock, water treatment and the production, processing, storage and packaging of food. To this end, a wide variety of nanomaterials, ranging from metals and inorganic metal oxides to organic nanomaterials carrying bioactive ingredients are applied. This review shows an overview of current and future applications of nanotechnology in the food industry. Food additives and materials in contact with food are now the main applications, while it is expected that in the future are in the field of nano-encapsulated and nanocomposites in applications as novel foods, additives, biocides, pesticides and materials food contact.

Nanotechnology in food industry II: risk assessment and legislation

Currently, there is increasing use of nanomaterials in the food industry thanks to the many advantages offered and make the products that contain them more competitive in the market. Their physicochemical properties often differ from those of bulk materials, which require specialized risk assessment. This should cover the risks to the health of workers and consumers as well as possible environmental risks. The risk assessment methods must go updating due to more widespread use of nanomaterials, especially now that are making their way down to consumer products. Today there is no specific legislation for nanomaterials, but there are several european dispositions and regulations that include them. This review gives an overview of the risk assessment and the existing current legislation regarding the use of nanotechnology in the food industry.

Principles of toxicology applied to nanotechnology: risk assessment

Background: Nanotechnologies are developing very rapidly and nanomaterials (NMs) are increasingly being used in a wide range of applications in science, industry and biomedicine.

Nanotechnology: radical new science or plus ça change?

Is a radical nanotechnology involving the construction of macroscopic products via software-directed manipulation of single molecules possible? Are we only a few decades away from a technological utopia where virtually any product may be constructed via molecular manufacturing? These and other similarly provocative questions formed the backdrop for a well-attended debate on nanotechnology held in the University of Nottingham last year (26 August 2005).

Broad Concerns about Nanotechnology Patents: Symptoms and Diagnosis

We discuss the concerns that the patenting activity in the new nanotechnologies could blur the line between what is considered a discovery and what can be considered as an invention. We find that the nature of nanotechnology products, research, and the development agendas in science and engineering fields that include biomimetics pose a challenge to the present practice of including chemicals as eligible patent subject matter. After revisiting the historical development of patent law and noting its divergence from the developments in science and technology, we introduce the distinction between simple and complex machines as these relate to chemistry and nanotechnology. This distinction poses the question of what is the logical category of inventions that fall within patentable subject matter given that patent law was conceived to cover simple machines, not complex ones.