Chemical Properties Of Nanostructures Research Articles

Fractal Nanocatalysis and Related Phenomena

The concept of nanofractality is developed. Models describing the appearance of nanofractality in objects of different dimensions are presented. For two-dimensionality, analysis is based on the modification of Tamm states on fractal surfaces. In this context, the appearance of different effects is analyzed. The fractality of the free and internal surfaces of nanoobjects is found to affect their electronic spectrum, which can lead to radical modification of the physical and chemical properties of nanostructures.

Tamm states of fractal surfaces

The theory of modification of surface Tamm states on fractal surfaces is developed, and manifestations of such phenomena are analyzed. The obtained results suggest that the fractality of free and inner surfaces of nanoobjects affects their electronic spectrum, which may lead to modification of the physical and chemical properties of nanostructures.

Effect of Cu-doped site and charge on the optical and magnetic properties of 55-atom Ag cluster: A density functional theory study

In this study, the structures and magnetic properties of Cu single-doped Ag clusters are investigated by density functional theory (DFT). The optical spectrum of their neutral and charged states (−1,+1) are then examined by improved time-dependent DFT. Results show that Cu-doped site and charge affects not only structural stability of Ag55 cluster but also its performances. Icosahedral Ag54Cu1center cluster with Ih is more stable than icosahedral Ag54Cu1middle and Ag54Cu1sur clusters with Cs about 0.792 and 0.480eV, respectively. Some prominent surface plasmonic resonance (SPR) peaks are observed in the absorption spectrum of these clusters particularly in the infrared region. Cu doping Ag55 cluster causes redshifts in the adsorption spectrum of Ag54Cu1middle (charged (−1) and neutral) and Ag54Cu1center clusters and blueshift in the adsorption spectrum of Ag54Cu1middle (charged (+1)) and Ag54Cu1sur cluster. The redshifts of SPR as well appear as a cluster changes from Ag55 to Ag54Cu1middle to Ag54Cu1center to Cu55 for the same charge. The Cu doping site has no effect on the magnetic properties of neutral clusters. However, Cu doped in the cluster center and with charge (+1) enhances the magnetic properties of the clusters four times compared with neutral clusters. Cu atom-doped and charge can tune physical and chemical properties of nanostructures and thus have many potential applications, especially in solar cells and sensors.

Potencial risks of nanoparticles

Nanotoxicology is an emergent important subdiscipline of Nanosciences, which refers to the study of the interactions of nanostructures with biological systems giving emphasis to the elucidation of the relationship between the physical and chemical properties of nanostructures with induction of toxic biological responses. Although potential beneficial effects of nanotechnologies are generally well described, the potential (eco) toxicological effects and impacts of nanoparticles have so far received little attention. This is the reason why some routes of expousure, distribution, metabolism, and excretion, as well as toxicological effects of nanoparticles are discussed in this review.

Toxicology Perspective of Nanopharmaceuticals: A Critical Review

For the last 10 years pharmaceutical research and industry has elucidated several innovations and practices in pharmaceutical nanotechnology. Due to the increasing use of nanoparticles, the risk of human exposure rapidly increases and reliable toxicity test systems are urgently needed. Nanotoxicology refers to the study of the interactions of nanostructures with biological systems with an emphasis on the relationship between the physical and chemical properties of nanostructures with induction of toxic biological responses. It involves their unique biodistribution, clearance, accumulation, immune response and metabolism. An understanding of the relationship between the physical and chemical properties of the nanostructure and their in-vivo behavior would provide a basis for assessing toxic response and more importantly could lead to better predictive models for assessing toxicity. The current regulations for nanoparticles containing products are still in a nascent stage. The advantages of nanoparticles led to failures in noticing the toxic outcomes in living organisms. Major changes are required by considering several factors including environmental, health and safety issues. The rapid commercialization of nanotechnology requires thoughtful open discussion of broader societal impacts and urgent toxicological oversight action.

Nanotoxicology : An Emerging Discipline

Nanotoxicology refers to the study of the interactions of nanostructures with biological systems with an emphasis on elucidating the relationship between the physical and chemical properties of nanostructures with induction of toxic biological responses. Nanotoxicology is aimed at providing information on the potential toxicological effects, risk assessment and safety evaluation of nanostructured materials on human health. Nanoparticles present possible dangers, both medically and environmentally. They are also able to pass through cell membranes in organisms and their interactions with biological systems are relatively unknown. Animal studies have shown that nanoparticles can penetrate cells and tissues, move through the body and brain and cause biochemical damage. The greater chemical reactivity of nanomaterials result in increased production of reactive oxygen species which may contribute to similar patterns of cell injury and alterations at the molecular level by initiation, propagation and autocatalytic chain reactions. Intracellular signaling activation and inactivation of enzymes, stimulation, secretion and release of pro-inflammatory cytokines, chemokines and nuclear factor activation and alteration are also common events.

Nanotoxicity: the growing need for in vivo study

Nanotoxicology is emerging as an important subdiscipline of nanotechnology. Nanotoxicology refers to the study of the interactions of nanostructures with biological systems with an emphasis on elucidating the relationship between the physical and chemical properties (e.g. size, shape, surface chemistry, composition, and aggregation) of nanostructures with induction of toxic biological responses. In the past five years, a majority of nanotoxicity research has focused on cell culture systems; however, the data from these studies could be misleading and will require verification from animal experiments. In vivo systems are extremely complicated and the interactions of the nanostructures with biological components, such as proteins and cells, could lead to unique biodistribution, clearance, immune response, and metabolism. An understanding of the relationship between the physical and chemical properties of the nanostructure and their in vivo behavior would provide a basis for assessing toxic response and more importantly could lead to predictive models for assessing toxicity. In this review article, we describe the assumptions and challenges in the nanotoxicity field and provide a rationale for in vivo animal studies to assess nanotoxicity.

Preface: phys. stat. sol. (a) 204/4

AbstractThis issue contains scientific contributions to the Fifth Brazilian–German Workshop on Applied Surface Science. The workshop was held in Brazil at the beautiful Hotel Portobello, Mangaratiba, a city located 100 km from Rio de Janeiro, from 3–7 April 2006.The meeting was attended by about 80 participants, with 29 invited talks and 43 poster presentations on current topics of surface science.As in previous meetings (1995 in Portobello, RJ, Brazil, 1998 in Döllnsee, Berlin, and 2001 in Itapema, SC, Brazil, 2003 in Ringberg‐Castle, Tegernsee), the program featured contributions to numerous issues in surface science both from the theoretical and the experimental point of view. In the field of materials science, important topics such as catalysis, magnetism, optics and the physics of devices were addressed by describing the structural, physical and chemical properties of nanostructures and films of inorganic (metals, alloys and oxides) and organic (polymers and biological molecules) materials.A substantial part of the success of the meeting is probably due to the relaxed atmosphere at the beach hotel on the green coast of Mangaratiba, where excellent scientific presentations were mixed with intense discussions among both senior and younger researchers.A significant moment came in the opening session, when a presentation in memory of Wolfgang H. P. Losch, his life and scientific achievements, was given by Prof. Horst Niehus. Prof. Losch was the first organizer of this series of meetings together with Prof. Niehus and passed away on 10 August 2004.The organizers of the Workshop, Fernando Lázaro Freire Jr. (Rio de Janeiro, Brazil), Hajo Freund (Berlin, Germany), Antonio Azevedo (Recife, Brazil), Horst Niehus (Berlin, Germany), André A. Pasa (Florianópolis, Brazil) and Eberhard Umbach (Würzburg, Germany), are greatly indebted to the following organizations for financial support: Deutsche Forschungsgemeinschaft (DFG), Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Finaciadora de Estudos e Projetos (FINEP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Universidade Federal de Santa Catarina (UFSC) and the specially created intergovernmental agreement between CAPES and DFG to promote such meetings.March 2007

Preface: phys. stat. sol. (a) 201/5

This issue contains scientific contributions to the 4th German/Brazilian Workshop on Applied Surface Science. The workshop was held in Germany at the beautiful Castle Ringberg conference site of the Max Planck Society, located 60 km from Munich, from 21–26 September 2003. The meeting was attended by about 50 participants, with 21 invited talks and 18 contributed presentations (8 oral and 10 posters) on relevant topics of surface science. As in previous meetings (1995 in Portobello, RJ, Brazil, 1998 in Döllnsee, Berlin, Germany, and 2001 in Itapema, SC, Brazil), a significant number of important questions in surface science were covered from both the theoretical and the experimental point of view. In the field of materials science, emphasis was given to the description of the structural, physical and chemical properties of nanostructures and films of inorganic (metals, alloys and oxides) and organic (polymers and biological molecules) materials. A substantial part of the success of the meeting can be attributed to the relaxed atmosphere at the castle, near the lake Tegernsee, where excellent scientific presentations were mixed with intense discussions among both senior and younger researchers. The event also led to the development of new and ongoing collaborations between partners from Brazil and Germany. The organizers of the Workshop, Israel J. R. Baumvol (Porto Alegre, Brazil), Hajo Freund (Berlin, Germany), Wolfgang H. P. Losch (Natal, Brazil), Horst Niehus (Berlin, Germany), André A. Pasa (Florianópolis, Brazil) and Eberhard Umbach (Würzburg, Germany), are greatly indebted to the following organizations for financial support: Deutsche Forschungsgemeinschaft (DFG), Fritz-Haber-Institut Berlin (FHI), Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Universidade Federal de Santa Catarina (UFSC) and the specially created intergovernmental agreement between CAPES and DFG to promote such meetings. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Reproducible lateral force microscopy measurements for quantitative comparisons of the frictional and chemical properties of nanostructures

Atomic force microscopy (AFM) is a widely used technique for characterizing the topography and frictional properties of nanostructures. Inherent misalignments between the AFM cantilever and the feedback hardware lead to crosstalk between topography data and lateral force microscopy (LFM) data. Because the degree of crosstalk depends on the positioning of the cantilever, LFM and topography data of the same structure can vary from one experiment to the next. For nanostructures with large LFM contrast, errors as large as 50% in topography and LFM can be observed. This paper describes an empirical strategy for correcting this alignment error. The technique is used to characterize the frictional properties of scanning probe-induced oxide nanostructures and the hydrogen-terminated Si(1 1 1) surfaces on which they are patterned. Reproducible differences in the frictional properties of the oxide nanostructures patterned on HF-treated and NH 4F-treated Si(1 1 1) surfaces are observed and attributed to the mixed-hydride versus monohydride termination of each surface. The observed frictional contrast is consistent with known differences in surface reactivity and demonstrates how LFM measurements can provide insight into the frictional and chemical properties of nanostructures