Advancements in the micro-and nano-scale fabrication techniques have opened up new avenues for the development of portable, scalable and easier-to-use biosensors. Over the last few years, electrodes made of carbon have been widely used as sensing units in biosensors due to their attractive physiochemical properties. The aim of this research is to investigate different strategies to develop functionalized high surface carbon micro/nano-structures for electrochemical and biosensing devices. High aspect ratio three-dimensional carbon microarrays were fabricated via carbon microelectromechanical systems (C-MEMS) technique, which is based on pyrolyzing pre-patterned organic photoresist polymers. To further increase the surface area of the carbon microstructures, surface porosity was introduced by two strategies, i.e. (i) using F127 as porogen and (ii) oxygen reactive ion etch (RIE) treatment. Electrochemical characterization showed that porous carbon thin film electrodes prepared by using F127 as porogen had an effective surface area (Aeff 185%) compared to the conventional carbon electrode. To achieve enhanced electrochemical sensitivity for C-MEMS based functional devices, graphene was conformally coated onto high aspect ratio three-dimensional (3D) carbon micropillar arrays using electrostatic spray deposition (ESD) technique. The amperometric response of graphene/carbon micropillar electrode arrays exhibited higher electrochemical activity, improved charge transfer and a linear response towards H2O2 detection between 250μM to 5.5mM. Furthermore, carbon structures with dimensions from 50 nano-to micrometer level have been fabricated by pyrolyzing photo-nanoimprint lithography patterned organic resist polymer. Microstructure, elemental composition and resistivity characterization of the carbon nanostructures produced by this process were very similar to conventional photoresist derived carbon. Surface functionalization of the carbon nanostructures was performed using direct amination technique. Considering the need for requisite functional groups to covalently attach bioreceptors on the carbon surface for biomolecule detection, different oxidation techniques were compared to study the types of carbon–oxygen groups formed on the surface and their percentages with respect to different oxidation pretreatment times. Finally, a label-free detection strategy using signaling aptamer/protein binding complex for platelet-derived growth factor oncoprotein detection on functionalized three-dimensional carbon microarrays platform was demonstrated. The sensor showed near linear relationship between the relative fluorescence difference and protein concentration even in the sub-nanomolar range with an excellent detection limit of 5 pmol.

Orientadores: Alexandre Leite Rodrigues de Oliveira, Eliana Aparecida de Rezende Duek / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-26T15:35:48Z (GMT). No. of bitstreams: 1 Assaf_Kyl_M.pdf: 4219247 bytes, checksum: 1f0af33b698c2094539d28e23f3f042b (MD5) Previous issue date: 2015 / Resumo: Lesões traumáticas de nervos periféricos podem gerar separação de seus cotos, impossibilitando a neurorrafia término-terminal. Nesses casos, os enxertos autólogos são muito utilizados, mas apresentam algumas desvantagens, como disponibilidade do tecido doador, formação de neuromas dolorosos na área doadora, entre outras. A técnica de tubulização, na qual são empregados tubos para orientar e proteger o nervo durante a regeneração, oferece vantagens como preservação da área doadora e possibilidade de manipulação do ambiente interno do tubo. Muitos aspectos do tubo a ser utilizado para regeneração nervosa devem ser considerados, como sua biocompatibilidade, biodegradabilidade, tempo de degradação, etc. A poli(?-caprolactona) (PCL) é um material que possui tais propriedades. Os nanotubos de carbono (NT1) e o grafeno (NTN) também possuem características que os tornam excelentes dispositivos para implantes neurais e para compor compósitos poliméricos. Neste trabalho, nervos isquiáticos de ratos Lewis foram transeccionados e tubulizados com PCL, PCL com nanotubos de carbono, PCL com óxido de grafeno e PCL com ambas as nanoestruturas. A caracterização dos nanocompósitos mostrou que as nanoestruturas tem boa dispersão, não alteram o grau de cristalinidade do PCL, oferecem reforço na matriz polimérica e provocam alteração na mobilidade molecular na parte amorfa do polímero. Na análise das próteses por microscopia eletrônica de varredura, os tubos NT1, NTN e também os confeccionados com a mistura deles, apresentaram um número importante de células aderidas, quando comparados ao PCL. Todos os materiais também se mostraram biocompatíveis. Na contagem das fibras nervosas e na comparação das áreas dos nervos, a mistura mostrou diferenças estatísticas em relação aos demais grupos experimentais (p<0,05). Porém, nas análises morfométricas não foram observadas diferenças entre os grupos. Ainda, a avaliação funcional dos animais não mostrou uma recuperação significativa da marcha. Contudo, a comparação das massas dos músculos sóleo e tibial anterior e a análise histológica desses, revelaram preservação de massa, sem atrofia das fibras musculares, indicando reinervação bem sucedida / Abstract: Injuries to peripheral nerves generate proximal and distal stumps, usually making end-to-end neurorrhaphy impossible. In such cases, autologous grafts are widely used, but have some disadvantages, such as availability of donor tissue, formation of painful neuromas in the donor area, etc. The tubulization technique, in which tubes are used to guide and protect the nerve during regeneration, offers advantages such as preservation of the donor nerve area and the possibility of manipulating the internal environment of the tube. Many aspects of the conduit to be used for nerve regeneration must be considered as biocompatibility, biodegradability, degradation time, etc. The poly (?-caprolactone) (PCL) is possesses most of these properties. Carbon nanotubes and graphene also have features that make them excellent devices for neural implants and to constitute polymer composites. In this work, sciatic nerves of Lewis rats were transected and tubulized with PCL, PCL with carbon nanotubes (NT1), PCL with graphene oxide (NTN) and PCL with both nanostructures. Nanocomposites characterization showed that nanoparticles have good dispersion, do not alter the degree of PCL crystallinity, provide reinforcement of the polymer matrix and cause changes in the molecular mobility in the amorphous part of the polymer. In the analysis of the prostheses by scanning electron microscopy, NT1, NTN and its mixture showed higher number of adhered cells as compared to the PCL. All materials were also biocompatible. The counting regenerated nerve fibers and comparison of the nerve areas, the mixture showed statistical differences when compared to the other experimental groups (p <0.05). Nevertheless, morphometric analyzes were not different among groups. Furthermore, functional evaluation of the animals showed no significant gait recovery after 8 weeks post surgery. However, comparison of the weigth of the soleus and anterior tibialis and the histological analysis revealed absence of atrophy and preservation of the tissue, indicating a successful reinervation / Mestrado / Biologia Celular / Mestra em Biologia Celular e Estrutural

Orientador: Silvio Antonio Sachetto Vitiello / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T00:18:16Z (GMT). No. of bitstreams: 1 Madeira_Lucas_M.pdf: 4273856 bytes, checksum: 8543c0dd916e2ec3fc638a5d31b32787 (MD5) Previous issue date: 2015 / Resumo: Nessa dissertação nós investigamos dois sistemas de muitos corpos. Na primeira parte nós escolhemos uma abordagem clássica para estudar a adsorção de gases nobres pesados, Ne, Ar, Kr, Xe e Rn, em substratos de grafeno. Nós apresentamos evidências de camadas adsorvidas comensuradas, as quais dependem fortemente da simetria do substrato, para duas estruturas: camadas de Ne na rede sqrt{7} X sqrt{7} e Kr na rede sqrt{3} X sqrt{3}. Para estudar o derretimento nós introduzimos um parâmetro de ordem e sua susceptibilidade. O calor específico e a susceptibilidade em função da temperatura foram calculados para os gases nobres pesados em diversas densidades. A posição e largura característica dos picos do calor específico e da susceptibilidade foram determinadas. Finalmente, nós investigamos a distância dos primeiros vizinhos e a distância entre a camada e o substrato, identificando contribuições relacionadas aos picos do calor específico e da susceptibilidade. A segunda parte da dissertação trata de uma linha de vórtice no gás unitário de Fermi. Gases fermiônicos ultrafrios são notáveis devido à possibilidade experimental de variar as interações interpartículas através de ressonâncias de Feshbach, o que possibilita a observação do crossover BCS-BEC. No meio do crossover encontra-se um estado fortemente interagente, o gás unitário de Fermi. Uma linha de vórtice corresponde a uma excitação desse sistema com unidades de circulação quantizadas. Nós construímos funções de onda, inspiradas na função BCS, para descrever o estado fundamental e também o sistema com uma linha de vórtice. Nossos resultados para o estado fundamental elucidam aspectos da geometria cilíndrica do problema. O perfil de densidade é constante no centro do cilindro e vai a zero suavemente na borda. Nós separamos a contribuição devido à parede da energia do estado fundamental e determinamos a energia por partícula do bulk, epsilon_0=(0.42 +- 0.01) E_{FG}. Nós também calculamos o gap superfluído para essa geometria, Delta=(0.76 +- 0.01) E_{FG}. Para o sistema com a linha de vórtice nós obtivemos o perfil de densidade, o qual corresponde a uma densidade não nula no centro do vórtice, e a energia de excitação por partícula, epsilon_{ex}=(0.0058 +- 0.0003) E_{FG}. Os métodos empregados nessa dissertação, Dinâmica Molecular, Monte Carlo Variacional e Monte Carlo de Difusão, nos dão uma base sólida para a investigação de sistemas relacionados, e outros sistemas, de muitos corpos no futuro / Abstract: In this dissertation we investigated two many-body systems. For the first part we chose a classical approach to study the adsorption of heavy rare-gases, Ne, Ar, Kr, Xe and Rn, on graphene substrates. We presented evidences of commensurate adlayers, which depend strongly on the symmetry of the substrate, for two structures: Ne adlayers in the sqrt{7} X sqrt{7} superlattice and Kr in the sqrt{3} X sqrt{3} lattice. In order to study the melting of the system we introduced an order parameter, and its susceptibility. The specific heat and susceptibility as a function of the temperature were calculated for the heavy noble gases at various densities. The position and characteristic width of the specific heat and susceptibility peaks of these systems were determined. Finally, we investigated the first neighbor distance and the distance between the adlayer and the substrate, identifying contributions related to specific heat and melting peaks. The second part of the dissertation deals with a vortex line in the unitary Fermi gas. Ultracold Fermi gases are remarkable due to the experimental possibility to tune interparticle interactions through Feshbach resonances, which allows the observation of the BCS-BEC crossover. Right in the middle of the crossover lies a strongly interacting state, the unitary Fermi gas. A vortex line corresponds to an excitation of this system with quantized units of circulation. We developed wavefunctions, inspired by the BCS wavefunction, to describe the ground state and also for a system with a vortex line. Our results for the ground state elucidate aspects of the cylindrical geometry of the problem. The density profile is flat in the center of the cylinder and vanishes smoothly at the wall. We were able to separate from the ground state of the system the wall contribution and we have determined the bulk energy as epsilon_0=(0.42 +- 0.01) E_{FG} per particle. We also calculated the superfluid pairing gap for this geometry, Delta=(0.76 +- 0.01) E_{FG}. For the system with a vortex line we obtained the density profile, which corresponds to a non-zero density at the core, and the excitation energy, epsilon_{ex}=(0.0058 +- 0.0003) E_{FG} per particle. The methods employed in this dissertation, Molecular Dynamics, Variational Monte Carlo and Diffusion Monte Carlo, give us a solid basis for the investigation of related and other many-body systems in the future / Mestrado / Física / Mestre em Física / 2012/24195-2 / FAPESP

Orientador: Abner de Siervo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T16:48:10Z (GMT). No. of bitstreams: 1 Ferreira_RodrigoCezardeCampos_M.pdf: 12900994 bytes, checksum: 7f4ff602b7e6aae7e2d8890e9f8d0a2b (MD5) Previous issue date: 2016 / Resumo: O grafeno é um alótropo bidimensional do carbono com hibridização do tipo sp2. Suas notáveis propriedades eletrônicas e estruturais provocaram um enorme interesse científico e tecnológico para o material na última década. Grafeno pode ser crescido em certos metais de transição através da técnica bem conhecida Chemical Vapor Deposition (CVD). A estabilidade do grafeno nesses substratos é garantida, porém as interações químicas entre eles modificam suas exóticas propriedades eletrônicas e estruturais. É possível sintetizar grafeno sobre Ir(111) sem defeitos estruturais substanciais e em um único domínio, quando realizado sob condições específicas de temperatura do substrato e da pressão do gás precursor (propileno). Na tentativa de isolar o grafeno do substrato, seja fisicamente ou eletricamente, existe a possibilidade da intercalação de diversas espécies, tais como gases, metais ou nanopartículas. Realizando tal procedimento, além da suspensão do material, é possível também dopar a banda eletrônica ou induzir abertura de gap. Neste contexto, o objetivo deste trabalho é estudar a dinâmica de crescimento e intercalação do ferro em Gr/Ir(111), seguindo os parâmetros termodinâmicos envolvidos e observando principalmente os deslocamentos químicos usando espectroscopia de fotoelétrons de raio-x (XPS) de alta resolução com síncrotron. Em paralelo, também usamos o microscópio de varredura por tunelamento (STM) para acompanhar a formação e intercalação das estruturas na superfície durante os ciclos de evaporação do ferro. Os resultados mostraram que, com o substrato à temperatura ambiente, o Fe interage fortemente com o grafeno e ocorre intercalação parcial. No caso de evaporação à temperaturas moderadas, houve intercalação total do Fe que permaneceu protegido pela folha de grafeno, indicando ser possível crescer um filme fino intercalado na superfície / Abstract: Graphene is a 2D carbon allotrope having sp2 hybridized atoms in a single-layer. Its remarkable electronic and structural properties attract an enormous scientific and technological interest to the material in the last decade. Graphene can be grown on certain transition metals by the well-known Chemical Vapor Deposition (CVD) technique. The stability of graphene in these substrates is guaranteed, but the chemical interactions between them modify its exotic electronic and structural properties. It is possible to grow graphene on the Ir(111) surface without substantial structural defects and withsingle domain, whenspecific conditions of substrate temperature and pressure of the precursor gas (propylene) are applied. While trying to retrieve the characteristic properties, the scientific community has been trying to isolate graphene from the metallic substrate, either physically or electrically, by intercalation of various species such as gases, metals or nanoparticles. By performing such procedures, it is possible, besides the desired suspension of the material, to induce changes such as gap opening and doping of the electronic band structures. In this context, the aim of this work is to study the dynamics of iron growth and intercalation in Gr/Ir(111), following the thermodynamic parameters involved and observing mainly the chemical shifts using high resolution x-ray photoelectron spectroscopy (XPS). In parallel, we also used the scanning tunneling microscope (STM) to follow the formation of Fe surface structures during the evaporation cycles and intercalation. The results show that at room temperature, Fe interacts strongly with graphene with partial intercalation. In the case of evaporation at moderate temperatures, there was full intercalation of Fe which remained protected by the graphene sheet / Mestrado / Física / Mestre em Física / 1423605/2014 / CAPES

A eletrônica molecular vem sendo investigada intensivamente por mais de vinte anos. Nesse sentido, as pesquisas científicas estão sendo focadas na busca de estruturas que possam ser utilizadas na construção de dispositivos em escalas nanométricas, que possam substituir a tecnologia tradicional do silício. O objetivo principal deste trabalho foi explorar as propriedades físicas de sistemas a base de grafano, um dos mais promissores materiais para serem usados como nanodispositivos. Para isso, foi realizada uma investigação teórica, baseada em cálculos de primeiros princípios, das propriedades estruturais e eletrônicas do grafeno numa forma pura ou com defeitos intrínsecos e extrinsecos. O primeiro grupo de estruturas investigadas foi o grafeno e grafano como nanofolhas constituídas por elementos do grupo IV da tabela periódica (C, SiC, Si, Ge e Sn). Também foram analisadas as mudanças nas propriedades eletrônicas do grafano do grupo IV com a substituição dos átomos de hidrogênio por flúor. A segunda parte do trabalho explorou as propriedades de defeitos estruturais em grafeno, tais como a monovacância, divacância, trivacância e Stone-Wales, e também o grafeno com dopantes (boro e nitrogênio) em diversas configurações. Todos os cálculos foram feitos utilizando métodos ab initio com base na teoria do funcional densidade. Foram estudadas algumas possíveis aplicações para os grupos de estruturas de grafeno investigados, através da análise de algumas de suas propriedades, tais como as densidades de estados próximas ao nível de Fermi e as estruturas de bandas eletrônicas para cada sistema. / The molecular electronics has been investigated for more than twenty years. In this sense, the scientific research has been focused on the search for structures that could be used in nanoelectronic devices that could replace the traditional silicon technology. The major goal of this work is to explore the physical properties of systems based on graphene, one of the most promising materials to be used in nanoelectronics. For that, an ab initio investigation was carried on the structural and electronic properties of graphene in its pristine form and with intrinsic and extrinsic defects. The first investigation explored the properties of group IV nanosheets (of C, SiC, Si, Ge e Sn), and the modifications on their properties as result of hydrogenation or fluorination. The second part of this work explored the physical properties of structural intrinsic defects in graphene, such as monovacancy, divacancy, trivacancy, and Stone-Wales ones. The work also explored the properties of boron and nitrogen dopants. All the calculations were performed using the ab initio methodology, based on the density functional theory.

Thesis (M. Sc. (Physics)) -- University of Limpopo, 2016. / Bilayer graphene and single-walled carbon nanotubes were studied through classical molecular dynamics using Tersoff potential. The Tersoff potential has been the most successful model to replicate much of the semiconducting properties in carbon structures. The simulations were performed within a canonical (NVT) ensemble for structural properties and isothermal–isobaric ensemble (NPT) for thermodynamic properties of both materials. The bilayer graphene consists of two models of 64 and 256 atoms. Single-walled carbon nanotubes consist of three chiral structures of 264 atoms which is cnt(12,10), 260 atoms which is cnt(10,12) and armchair structure of 312 atoms which is cnt(12,12). The structural and thermodynamics properties were investigated in a range of temperature from 300 - 5000 K. It has been found that some of the properties of the graphene and carbon nanotube are similar. Graphene256 was found to be more stable than graphene64 and the armchair cnt(12,12) appears to be more mechanically stable than chiral cnt(12,10). Graphene and single-walled carbon nanotubes were also studied using X-ray diffraction and atomic force microscopy (AFM). The lattice constant for both materials were calculated and they agree well with the computational results. For carbon nanotubes, different solvents were used for characterization using the AFM. Chloroform was the best solvent since we managed to find some bundles of carbon nanotube. For ethanol and toluene solvents we did not managed to get any bundles. The diameter of single-walled carbon nanotube was determined only on a solution that chloroform solvent was used.

The capability of light goes well beyond illumination, yet it is so underused in our lives because the control of light still largely relies on clumsy bulk lenses. Less than 10 years ago, a type of revolutionary devices made of nanometer scale optical elements – metasurfaces – was invented to control the light propagation and its energy dissipation with arbitrary degree of freedom, at unprecedentedly small volumes (although some would argue that the advent of metasurfaces came in the 1990s). Vast diversity of new discoveries has since been made possible, and many more existing applications have seen significant performance enhancement with the aid of metasurfaces.<div><br><div> <div>In the scope of this work, I explore the use of a variety of metasurfaces to address several existing real-world challenges: sensing, optical heating, and data storage. Among these, three metasurfaces involve the world’s first two-dimensional material, graphene. I first investigate the graphene plasmonic resonator, which have been shown to be extremely sensitive single-molecule sensors. Graphene also has many intriguing properties in photodetection applications, such as lightweight, ultra-wide detection band, and ultrafast response speed. I have used two different metasurfaces to enhance the intrinsically low responsivity (sensitivity) of graphene photodetectors. Amidst the discussion of graphene photodetectors, I show the characterization result of plasmonic heating of metasurfaces, an essential process of the graphene photo-responsivity enhancement. Lastly, I present a multi-functional metasurface which can be used in optical steganography, encryption, and data storage. The proposed metasurface is compatible with large scale parallel readout, which outperforms current Blu-ray technology in both storage capacity and readout speed</div></div></div>

Transmission electron microscopy (TEM) is an important tool for the characterization of materials as it can provide clear understanding of the relationship between structure, property and composition of nanomaterials. For this, the in-situ TEM analysis is performed and requires specially manufactured sample holders. In particular, those designed to carry out electrical biasing can be used to understand not just the I-V characteristics but also the failure mechanism, structure-property relationship, Joule heating dynamics, electromigration, field emission properties, etc. at the nanoscale. The platforms holding the sample in most modern in-situ TEM holders rely on an insulating ceramic membrane which needs to be (almost) transparent to the imaging electron beam. Electrodes are defined through lithography and patterned on this membrane. Unfortunately, the presence of this membranes introduces several limitations such as electrostatic charging, reduction of image contrast and poor mechanical stability. To circumvent this issue it is necessary to fabricate a novel type of sample platform which does not rely on the presence of a membrane. In this work, novel membraneless sample-holding platforms were designed and manufactured using advanced microfabrication methods and tools. Besides fitting into an array of analytical tools, the novel platforms (or “chips”) can be subjected to thermal and/or chemical processing without compromising their function or structure. To test these, the electrical response of one-, two- and zero-dimensional nanoparticles were studied. Firstly, we investigated current-induced modifications in silver nanowires and expandable graphite flakes and studied various phenomenon involved. Along with these, corresponding ex-situ studies were also performed. Next, graphene oxide was explored as an alternative support platform for in-situ TEM. We successfully achieved temperature as high as 2000o C by Joule heating of graphene oxide. Furthermore, this graphene oxide platform was used as a heater and chemical processing substrate for investigating thermal stability and synthesis of inorganic nanoparticles, respectively.

Crystal symmetry and elemental composition play a critical role in determining the physical properties of materials. In layered van der Waals (vdW) heterostructures, a two-dimensional (2D) material layer can be influenced by interactions between adjacent layers, dictating that the measured properties of the combined system will be in part derived from the geometric structure within the active layers. This thesis examines active crystal symmetry tuning in composite heterostructures of two-dimensional (2D) materials, engineered via nanomechanically assisted twist angle control, and designed by careful consideration of lowest energy stacking configurations. The material systems, devices, and experimental setups described in this thesis constitute a platform featuring highly programmable properties that are on-demand and reversible. Two prototypical systems are discussed in detail. The first is graphene encapsulated between boron nitride (BN) crystals, wherein the alignment state between the three layers is controlled. The second is the same system, but with no graphene between the encapsulating BN layers. In both systems, a long-wavelength geometric interference pattern, also known as a moiré pattern, forms between the adjacent crystals as a consequence of lattice-constant mismatch and twist angle. The moiré pattern caries its own symmetry properties that are also demonstrated to be tunable, and can be thought of as an artificially constructed superlattice of periodic potential with wavelength much greater than the lattice constants of the constituent layers. In the BN-encapsulated graphene system we show drastic tunability of band gaps at primary and secondary Dirac points (PDP and SDPs) indicating reversible on-demand inversion symmetry breaking, as well as evidence of dual coexisting moiré superlattices and additional higher-order interference patterns that form between them. The all-BN system shows substantial enhancement and suppression of second harmonic generation (SHG) response from the vdW interface between the BN crystals when the quadrupole component of the SHG response is engineered to be minimal, by controlling for total layer number and layer number parity. Changes in the physical properties of each composite system are measured with a combination of electronic transport measurements, and optical measurements (Raman and SHG), as well as piezo-force microscopy (PFM) measurements that give direct imaging of the moiré pattern. A number of invented and adapted fabrication and actuation techniques for controlling the twist angle of a bulk vdW crystal are discussed, and in the latter portion of this thesis these techniques are extended to include actuation of monolayer flakes of 2D crystals. In this discussion several case studies are discussed, including twist angle control for a single sample monolayer tungsten diselenide on monolayer molybdenum diselenide, as well as twist angle control for twisted bilayer graphene and graphene on BN. Additionally, a novel in-plane bending mode for graphene on BN is demonstrated using similar techniques. Further discussion of actuation via traditional electrostatic MEMS techniques is also included, illustrating complete on-chip control for on-demand nanomechanical actuation of 2D materials in vdW heterostructures.

A strong argument can be made that physics is, at its core, the study of symmetries. Nonlinear optics is certainly no exception, with an enormous number of distinct processes each depending in its own way on the underlying symmetries of the physical system, the light, or of nature itself. Restricting ourselves to optical harmonic generation, we will explore three unique physical systems as well as three symmetries. In each case, the controlled breaking of that symmetry will lead to optical enhancements, novel nonlinearities, or deep physical insights. Beginning with silicon metasurfaces, we will explore the effects of even and odd spatial symmetries in optical systems. The periodic breaking of this symmetry will lead us to the highly engineerable physics of bound states in the continuum. By studying the harmonic emission from an atomic gas in the volume surrounding the metasurface, we will come to understand that significant nonlinear optical enhancements can be engineered with any linewidth and at any wavelength. In the context of the two-dimensional material hexagonal boron nitride, we will investigate and break crystal inversion symmetries. Using an intense laser tuned to the phonon resonance of hexagonal boron nitride, large amplitude anharmonic ionic motions will provide us a powerful degree of control over the internal symmetries of the system at an atomic level. Breaking this symmetry, we measure short-lived even-order nonlinearities that would otherwise be forbidden in equilibrium. Our observations for second- and third- harmonic generation are confirmed by time-dependent density functional theory. Those simulations further extend the understanding of this symmetry-breaking effect to even higher order processes. Lastly, single-crystal graphene and graphite provide an ideal platform through which to explore time-reversal symmetry. Chiral photons, or optical beams with ellipticity and handedness, are well known to break time-reversal symmetry. While applying high-power, chiral light to graphene, the breaking of time-reversal lifts a degeneracy of the K and K’ valleys in the momentum space Brillouin zone. Lifting this degeneracy, we unveil underlying spatial symmetry properties of graphene in odd-order third- and fifth- harmonic generation which should otherwise be unobservable. We also show experimentally, for the first time, that valley polarization and population can be extracted using our technique.