Surface-Enhanced Raman Spectroscopy as a Probe of the Surface Chemistry of Nanostructured Materials

Surface-enhanced Raman spectroscopy (SERS) is now widely used as a rapid and inexpensive tool for chemical/biochemical analysis. The method can give enormous increases in the intensities of the Raman signals of low-concentration molecular targets if they are adsorbed on suitable enhancing substrates, which are typically composed of nanostructured Ag or Au. However, the features of SERS that allow it to be used as a chemical sensor also mean that it can be used as a powerful probe of the surface chemistry of any nanostructured material that can provide SERS enhancement. This is important because it is the surface chemistry that controls how these materials interact with their local environment and, in real applications, this interaction can be more important than more commonly measured properties such as morphology or plasmonic absorption. Here, the opportunity that this approach to SERS provides is illustrated with examples where the surface chemistry is both characterized and controlled in order to create functional nanomaterials.

Morphologically Diverse Cerium Oxide Nanostructures and Nanofields for Multi functional applications.

The prospective impact of nanomaterials in science and technology has followed an increasing trend due to their unique chemical and physical properties compared to bulk. Significant advances in current technologies in areas such as clean energy production, electronics, medicine, and environment have fuelled major research and development efforts in nanotechnology around the world. This leads to the opportunity to use such nanostructured materials in novel applications and devices. Ceria, zirconia, alumina and titania are some of the major oxides which find vast applications as a nanomaterial on a wider side.

Investigations on the structural, optical and magnetic properties of nanostructured cerium oxide in pure and doped forms and its polymer nanocomposites

In recent years, nanoscience and nanotechnology has emerged as one of the most important and exciting frontier areas of research interest in almost all fields of science and technology. This technology provides the path of many breakthrough changes in the near future in many areas of advanced technological applications. Nanotechnology is an interdisciplinary area of research and development. The advent of nanotechnology in the modern times and the beginning of its systematic study can be thought of to have begun with a lecture by the famous physicist Richard Feynman. In 1960 he presented a visionary and prophetic lecture at the meeting of the American Physical Society entitled “there is plenty of room at the bottom” where he speculated on the possibility and potential of nanosized materials. Synthesis of nanomaterials and nanostructures are the essential aspects of nanotechnology. Studies on new physical properties and applications of nanomaterials are possible only when materials are made available with desired size, morphology, crystal structure and chemical composition. Cerium oxide (ceria) is one of the important functional materials with high mechanical strength, thermal stability, excellent optical properties, appreciable oxygen ion conductivity and oxygen storage capacity. Ceria finds a variety of applications in mechanical polishing of microelectronic devices, as catalysts for three-way automatic exhaust systems and as additives in ceramics and phosphors. The doped ceria usually has enhanced catalytic and electrical properties, which depend on a series of factors such as the particle size, the structural characteristics, morphology etc. Ceria based solid solutions have been widely identified as promising electrolytes for intermediate temperature solid oxide fuel cells (SOFC). The success of many promising device technologies depends on the suitable powder synthesis techniques. The challenge for introducing new nanopowder synthesis techniques is to preserve high material quality while attaining the desired composition. The method adopted should give reproducible powder properties, high yield and must be time and energy effective. The use of a variety of new materials in many technological applications has been realized through the use of thin films of these materials. Thus the development of any new material will have good application potential if it can be deposited in thin film form with the same properties. The advantageous properties of thin films include the possibility of tailoring the properties according to film thickness, small mass of the materials involved and high surface to volume ratio. The synthesis of polymer nanocomposites is an integral aspect of polymer nanotechnology. By inserting the nanometric inorganic compounds, the properties of polymers can be improved and this has a lot of applications depending upon the inorganic filler material present in the polymer.

It’s a Trap! Unravelling Reversible Charge Trapping in Nanocrystals Through Single Particle and Ensemble Studies

Thesis (Ph.D.)--University of Washington, 2016-08

Understanding the Reaction Mechanism of Nanocomposite Thermites

Nanocomposite energetics are a relatively new class of materials that combine nanoscale fuels and oxidizers to allow for the rapid release of large amounts of energy. In thermite systems (metal fuel with metal oxide oxidizer), the use of nanomaterials has been illustrated to increase reactivity by multiple orders of magnitude as a result of the higher specific surface area and smaller diffusion length scales. However, the highly dynamic and nanoscale processes intrinsic to these materials, as well as heating rate dependencies, have limited our understanding of the underlying processes that control reaction and propagation. For my dissertation, I have employed a variety of experimental approaches that have allowed me to probe these processes at heating rates representative of free combustion with the goal of understanding the fundamental mechanisms. Dynamic transmission electron microscopy (DTEM) was used to study the in situ morphological change that occurs in nanocomposite thermite materials subjected to rapid (10^11 K/s) heating. Aluminum nanoparticle (Al-NP) aggregates were found to lose their nanostructure through coalescence in as little as 10 ns, which is much faster than any other timescale of combustion. Further study of nanoscale reaction with CuO determined that a condensed phase interfacial reaction could occur within 0.5-5 µs in a manner consistent with bulk reaction, which supports that this mechanism plays a dominant role in the overall reaction process. Ta nanocomposites were also studied to determine if a high melting point (3280 K) affects the loss of nanostructure and rate of reaction. The condensed phase reaction pathway was further explored using reactive multilayers sputter deposited onto thin Pt wires to allow for temperature jump (T-Jump) heating at rates of ~5x10^5 K/s. High speed video and a time of flight mass spectrometry (TOFMS) were used to observe ignition temperature and speciation as a function of bilayer thickness. The ignition process was modeled and a low activation energy for effective diffusivity was determined. T-Jump TOFMS along with constant volume combustion cell studies were also used to determine the effect of gas release in nanoparticle systems by comparing the reaction properties of CuO and Cu2O.

Efficient and Durable Vaccine against Intimin β of Diarrheagenic E. Coli Induced by Clay Nanoparticles

Improved strategies are urgently required to control infections with enterohemorrhagic Escherichia coli and enteropathogenic E. coli, two dominant zoonotic enteric pathogens responsible for a wide spectrum of illnesses as well as deaths of human being, with tremendous financial cost worldwide. The present study investigates the capacity of two clay nanoparticles (NPs) with opposite surface charges, namely synthetic layered double hydroxide (LDH) and hectorite (HEC) NPs as adjuvants to promote strong immune responses against the infections. Here both LDH and HEC NPs are showed to be able to carry an appreciable amount of Intimin β (1.1 and 4.4 mg per mg clay nanomaterials, respectively) and significantly facilitate antigen uptake by antigen-presenting cells. Remarkably, these clay NPs induce strong antibody and cell-mediated immune responses, which are much higher than that by the potent adjuvant, QuilA. Furthermore, these strong immune responses are well maintained for at least four months in the mouse model, during which there are no changes in histopathology of the animal organs. Collectively these data demonstrate the suitability of LDH and HEC NPs as useful adjuvants in new-generation vaccine formulations to control various infectious diseases.

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.

Synteza, modyfikacja powierzchni i charakterystyka fizykochemiczna wielofunkcyjnych nanomateriałów luminescencyjnych zawierających jony pierwiastków ziem rzadkich

Wydział Chemii: Zakład Ziem Rzadkich

Cyto- and Genotoxicity assessment of manufactured nano cerium dioxide in the A549 cell line

In the past decades the growing application of nanomaterials (NMs) in diverse consumer products has raised various concerns in the field of toxicology. They have been extensively used in a broad range of applications and cover most of the industrial sectors as well as the medicine and the environmental areas. The most common scenarios for human exposure to NMs are occupational, environmental and as consumers and inhalation is the most frequent route of exposure, especially in occupational settings. Cerium dioxide NMs (nano-CeO2) are widely used in a number of applications such as in cosmetics, outdoor paints, wood care products as well as fuel catalysts. For such reason, nano-CeO2 is one of the selected NMs for priority testing within the sponsorship program of the Working Party of Manufactured Nanomaterials of the OECD. In this context, the aim of this study is to assess the safety of nano-CeO2 (NM-212, Joint Research Center Repository) through the characterization of its cytotoxicity and genotoxicity in a human alveolar epithelial cell line. A dispersion of the NM in water plus 0.05% BSA was prepared and sonicated during 16 minutes, according to a standardized protocol. DLS analysis was used to characterize the quality of the NM dispersion in the culture medium. To evaluate the cytotoxicity of nano-CeO2 in the A549 cell line, the colorimetric MTT assay was performed; the capacity of cells to proliferate when exposed to CeO2 was also assessed with the Clonogenic assay. The genotoxicity of this NM was evaluated by the Comet Assay (3 and 24h of exposure) to quantify DNA breaks and the FPG-modified comet assay to assess oxidative DNA damage. The Cytokinesis-Block Micronucleus (CBMN) assay was used to further detect chromosome breaks or loss. The nano-CeO2 particles are spherical, displaying a diameter of 33 nm and 28 m2/g of surface area. The results of the MTT assay did not show any decreased in cells viability following treatment with a dose-range of nano-CeO2 during 24h. Nevertheless, the highest concentrations of this NM were able to significantly reduce the colony forming ability of A549 cells, suggesting that a prolonged exposure may be cytotoxic to these cells. Data from both genotoxicity assays revealed that nano-CeO2 was neither able to induce DNA breaks nor oxidative DNA damage. Likewise, no significant micronucleus induction was observed. Taken together, the present results indicate that this nano-CeO2 is not genotoxic in this alveolar cell line under the tested conditions, although further studies should be performed, e.g., gene mutation in somatic cells and in vivo chromosome damage (rodent micronucleus assay) to ensure its safety to human health.

Efeitos bioquímicos da exposição ao nanomaterial óxido de grafeno em diferentes tecidos do camarão branco (Litopenaeus vannamei; Crustacea, Decapoda), através da suplementação na ração

O desenvolvimento da nanotecnologia vem se intensificando nos últimos anos. Sendo que os NM já estão sendo utilizados em vários produtos disponíveis no mercado. Dentre os NM mais utilizados estão os compostos de carbono que embora sejam compostos somente por este elemento podem ter estruturas diferentes que refletem em suas aplicações e possivelmente em seus efeitos. Dentre os NM de carbono, o grafeno e o óxido de grafeno apresentam promissoras características que ampliam sua utilização em diversos segmentos desde eletrônicos até a distribuição de medicamentos. A intensificação da produção e utilização destes NM é acompanhada pela liberação destes nanomateriais no ambiente que pode afetar os organismos vivos, principalmente os animais aquáticos. Entretanto, pouco se sabe sobre os efeitos do óxido de grafeno em crustáceos de importância comercial como é o caso do camarão branco Litopenaeus vannamei. Portanto, a presente dissertação teve como objetivo avaliar os efeitos biológicos da exposição ao óxido de grafeno em diferentes tecidos do camarão.

Interação da cianotoxina microcistina e o nanomaterial de carbono fulereno (C60) em brânquias do peixe Cyprinus carpio (Teleostei: Cyprinidae) sob incidência de radiação UVA

A produção mundial de nanomateriais tem aumentado nos últimos anos, em função de suas variadas aplicações tecnológicas e, como consequência do seu crescente uso e demanda, poderão existir riscos ambientais sendo a água o ambiente onde muitas destas substâncias podem exercer efeitos deletérios. Um dos nanomaterias de carbono mais utilizados é o fulereno, um composto orgânico lipofílico que pode se comportar como carreador de moléculas tóxicas, potencializando a entrada de contaminantes ambientais em órgãos específicos, fenômeno conhecido como “cavalo de Troia”. As microcistinas (MC) são cianotoxinas produzidas por cianobactérias durante episódios de floração, afetando aos organismos aquáticos e ao ser humano. Diversos estudos demonstram que organismos expostos tanto às MCs quanto ao fulereno podem causar produção excessiva de espécies ativas de oxigênio e alterar os níveis de antioxidantes. Além disso, outro fator que pode vir a intensificar o potencial tóxico de ambos é a incidência de radiação UVA. Sendo assim, procurou-se avaliar os efeitos em parâmetros de estresse oxidativo da co-exposição ex vivo da cianotoxina microcistina-LR (MC-LR) e o nanomaterial de carbono fulereno em brânquias do peixe Cyprinus carpio sob incidência de radiação UVA. Os resultados mostraram que: (a) houve uma perda da capacidade antioxidante no tratamento com MC-LR (baixa concentração) quando coexposta com fulereno no UVA em relação com o tratamento realizado sem co-exposição com fulereno; (b) o fulereno no UV diminuiu a atividade da enzima glutationa-Stransferase (GST) quando comparado com o controle no UV; (c) a MC-LR (alta concentração) co-exposta com fulereno foi capaz de diminuir as concentrações do antioxidante glutationa (GSH) quando comparado com o mesmo tratamento tanto no UVA quanto no escuro sem a co-exposição ao fulereno; (d) o tratamento MC-LR (baixa concentração) com UVA aumentou o dano oxidativo lipídico quando comparado com o controle UVA; (e) o fulereno não causou uma maior bioacumulação da microcistina no tecido. Sendo assim, pode-se concluir que o fulereno não apresentou o potencial de carregador de moléculas nessas concentrações de microcistina, porém, a co-exposição dos compostos diminuem tanto capacidade antioxidante total, como a concentração da GSH, podendo gerar problemas a longo prazo na detoxificação da toxina.

How to design the surface of peptide-loaded nanoparticles for efficient oral bioavailability?

International audience

Are iron oxide nanoparticles safe? Current knowledge and future perspectives

Due to their unique physicochemical properties, including superparamagnetism, iron oxide nanoparticles (ION) have a number of interesting applications, especially in the biomedical field, that make them one of the most fascinating nanomaterials. They are used as contrast agents for magnetic resonance imaging, in targeted drug delivery, and for induced hyperthermia cancer treatments. Together with these valuable uses, concerns regarding the onset of unexpected adverse health effects following exposure have been also raised. Nevertheless, despite the numerous ION purposes being explored, currently available information on their potential toxicity is still scarce and controversial data have been reported. Although ION have traditionally been considered as biocompatible - mainly on the basis of viability tests results - influence of nanoparticle surface coating, size, or dose, and of other experimental factors such as treatment time or cell type, has been demonstrated to be important for ION in vitro toxicity manifestation. In vivo studies have shown distribution of ION to different tissues and organs, including brain after passing the blood-brain barrier; nevertheless results from acute toxicity, genotoxicity, immunotoxicity, neurotoxicity and reproductive toxicity investigations in different animal models do not provide a clear overview on ION safety yet, and epidemiological studies are almost inexistent. Much work has still to be done to fully understand how these nanomaterials interact with cellular systems and what, if any, potential adverse health consequences can derive from ION exposure.

Efeitos tóxicos induzidos pelos nanomateriais Fulereno (C60) e Nanoprata no Poliqueto Laeonereis Acuta (Nereididae) e nas comunidades bacterianas que habitam sua superfície corporal

O fulereno (C60) pertence a uma família de nanomateriais (NM) constituída exclusivamente de átomos de carbono, sendo encontrado na forma de suspensão na água (nC60). A nanoprata (nAg) possui um excepcional e amplo espectro bactericida e um custo de fabricação relativamente baixo. No entanto, pouco se sabe a respeito dos eventuais efeitos tóxicos induzidos por estes NM em organismos estuarinos. O poliqueto Laeonereis acuta tem o muco colonizado por comunidades bacterianas. Há registros de que L. acuta apresenta um gradiente corporal para concentração de EAO e capacidade antioxidante total. Neste estudo, os poliquetos foram expostos in vivo durante 24 horas ao nC60 e à nAg, separadamente. Após isso, as unidades formadoras de colônias (UFC) bacterianas foram contadas e pesadas, além de serem realizadas diversas medições bioquímicas nos poliquetos e nas bactérias. Os números de UFC bacterianas expostas ao nC60 foi menor na concentração de 0.01mg/L e os números de UFC bacterianas expostas à nAg foram similares aos dados de biomassa, diminuindo na maior concentração (1.0 mg/L) (p<0.05). A capacidade antioxidante contra radicais peroxil em homogeneizados bacterianos expostos ao nC60 foi menor na concentração de 0.1mg/L quando comparado ao controle (p<0.05). A região anterior apresentou menor capacidade antioxidante (p<0.05) nos poliquetos expostos a 1.0 mg/L, quando comparado ao controle. Os poliquetos expostos à nAg apresentaram menor capacidade antioxidante na região posterior na concentração de 1.0 mg/L quando comparado ao controle (p<0.05). O conteúdo de peróxidos lipídicos (TBARS) foi reduzido na região anterior dos poliquetos expostos nas duas menores concentrações ( 0.01 e 0.1 mg/L) de nC60 (p<0.05). Na região corporal posterior, somente os organismos expostos a maior concentração de nC60 (1.0 mg/L) mostraram aumento na concentração de TBARS quando comparado ao grupo controle (p<0.05). A atividade da enzima glutationa-Stransferase (GST) foi aumentada (p<0.05) na região média e posterior dos poliquetos expostos a 0.1 mg/L de nC60. Como conclusões pode se dizer que os dois NM induziram efeitos tóxicos ainda numa situação (escuridão) onde o fulereno não é fotoexcitado. O aumento na produção e comercialização de produtos com NM levanta a questão dos riscos ambientais associados ao desenvolvimento da nanotecnologia.