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Nanoparticles

I'm taking these notes to understand nanoparticles in general, but also to understand Soni chechi's PhD research on "the origin of chirality at nanoscale by studying the optical activity in carbon nanodots and plasmonic nanoparticles."

  • The origin of chirality at nanoscale
    • By studying the optical activity in
      • Carbon Nanodots
      • Plasmonic Nanoparticles

Types of Nanoparticles: At a Glance

  • Quantum Dot Semiconductors
  • Carbon Quantum Dots (Carbon Nanodots)
  • Carbon Nanotubes
  • Plasmonic Nanoparticles (Metal Nanoparticles)
  • Graphene
  • Metal-Organic Frameworks

Classification

Size: Metal nanoparticles can be classified based on their size into categories like nanoparticles (1-100 nm), nanoclusters (2-10 nm), and nanocrystals (10-100 nm).

Shape: Metal nanoparticles can have different shapes such as spheres, rods, wires, cubes, and plates. The shape of the nanoparticles can affect their properties and applications.

Composition: Metal nanoparticles can be made from different metals such as gold, silver, platinum, copper, and more. Each metal nanoparticle has unique properties and applications.

Surface properties: The surface of metal nanoparticles can be modified with different ligands or functional groups, which can affect their stability, reactivity, and interactions with other molecules.

Surface plasmon resonance: Some metal nanoparticles exhibit surface plasmon resonance (SPR), a phenomenon where the electrons on the nanoparticle's surface oscillate in response to light, giving them unique optical properties.

Details of Specific Nanoparticles

Plasmonic Nanoparticles

  • Plasma (State of Matter)
    • Surface Plasma
      • Plasmonic Oscillations
        • Surface Plasmons
        • Plasmonic Nanoparticles

Surface plasma and surface plasmons are related phenomena, but they have different meanings.

Surface plasma typically refers to the collective oscillations of free electrons at the interface between a metal and a dielectric material. This can lead to the formation of a surface plasma wave, which is a type of electromagnetic wave that propagates along the interface.

Surface plasmons specifically refer to the quanta of these collective oscillations. Surface plasmons are the quantized version of the surface plasma waves, and they can interact with light to give rise to phenomena such as surface-enhanced Raman scattering and localized surface plasmon resonance.

Uses of Nanoparticles

Plasmonic Nanoparticles

  • Cancer Treatment
  • Plasmonic Solar Cells
  • High Resolution Spectroscopy

Optical Activity: Notes

Optical activity in plasmonic nanoparticles and carbon nanodots refers to their ability to interact with and affect the polarization of light. When these nanostructures exhibit optical activity, it means that they can rotate the plane of polarized light passing through them.

In plasmonic nanoparticles, which are metallic nanoparticles that can support surface plasmon resonances, optical activity can arise from the chiral shape or arrangement of the nanoparticles. This optical activity can be utilized in various applications, including chiral sensing, optical signal modulation, and biological imaging.

Carbon nanodots, on the other hand, are carbon-based nanoparticles with unique optical properties. Optical activity in carbon nanodots can indicate their chiral structure or surface functionalization, which can influence their interactions with light and other molecules. This property is important in applications such as bioimaging, sensing, and optoelectronics.

Surface Plasmon Resonance

Surface plasmon resonance (SPR) is a phenomenon that occurs when metal nanoparticles interact with light. When light strikes the surface of a metal nanoparticle, it can cause the conduction electrons on the nanoparticle's surface to collectively oscillate. This collective oscillation of electrons is known as a surface plasmon.

The interaction between light and the surface plasmon results in the absorption of light at a specific wavelength, known as the plasmon resonance wavelength. This absorption of light leads to a strong enhancement of the electromagnetic field near the nanoparticle's surface.

Surface plasmon resonance is widely used in various applications, including:

Sensing: SPR is commonly used in biosensors to detect biomolecular interactions. Changes in the refractive index near the metal nanoparticle surface, caused by biomolecular binding events, can be detected by monitoring the shift in the plasmon resonance wavelength.

Imaging: SPR-based techniques, such as surface-enhanced Raman scattering (SERS), can be used for high-resolution imaging of biological samples and materials.

Catalysis: Surface plasmon resonance can enhance the catalytic activity of metal nanoparticles, making them effective catalysts for various chemical reactions.

Optical devices: Plasmonic nanoparticles can be used in the development of optical devices, such as photodetectors, light-emitting diodes, and solar cells.

Popular Nanoparticles: AI Notes

For a tech-savvy nerd interested in nanoparticles, here are some key types of nanoparticles that you might find intriguing:

Metal Nanoparticles: Including gold, silver, platinum, and copper nanoparticles, known for their unique optical, catalytic, and electronic properties.

Carbon Nanotubes: Cylindrical carbon structures with exceptional mechanical strength, electrical conductivity, and thermal properties, making them valuable in various fields like electronics and materials science.

Quantum Dots: Semiconductor nanoparticles with quantum confinement effects, offering tunable optical properties and applications in displays, imaging, and solar cells.

Lipid Nanoparticles: Used in drug delivery systems for their biocompatibility and ability to encapsulate and deliver therapeutic agents to specific targets in the body.

Polymeric Nanoparticles: Made from biodegradable polymers, these nanoparticles are used in drug delivery, imaging, and tissue engineering due to their versatility and controlled release capabilities.

Magnetic Nanoparticles: Comprising materials like iron oxide, these nanoparticles have applications in magnetic resonance imaging (MRI), targeted drug delivery, and hyperthermia treatment.

Silica Nanoparticles: Known for their high surface area and biocompatibility, silica nanoparticles are used in drug delivery, imaging, and as supports for catalysts.

Classification of Metal Nanoparticles: AI Notes

Size: Nanoparticles are typically classified based on their size. Ultrafine particles are in the range of 1-100 nm, while nanoparticles are slightly larger, ranging from 1-1000 nm.

Shape: Nanoparticles come in various shapes such as spherical, rod-shaped, triangular, or more complex structures like nanostars. The shape of the nanoparticle can affect its properties and applications.

Composition: Metal nanoparticles can be made from different metals like gold, silver, copper, or platinum. The choice of metal can influence the nanoparticle's behavior and applications.

Properties: Nanoparticles can exhibit different properties based on their composition and structure. For example, some metal nanoparticles are magnetic, while others may have catalytic properties.

Synthesis Methods: Metal nanoparticles can be synthesized using various methods such as chemical reduction, sol-gel processes, physical vapor deposition, and green synthesis methods using plant extracts or microorganisms. Each method can result in nanoparticles with different sizes, shapes, and properties.

Surface Chemistry: The surface chemistry of metal nanoparticles, including the presence of ligands or stabilizing agents, can significantly impact their stability, reactivity, and interactions with other molecules. Surface chemistry plays a crucial role in determining the behavior of nanoparticles in different environments.

Surface Modifications: Metal nanoparticles can undergo surface modifications to tailor their properties for specific applications. Surface functionalization with organic molecules, polymers, or biomolecules can enhance stability, biocompatibility, and functionality, making them suitable for diverse fields such as medicine, catalysis, and sensing.

Optical Properties: Metal nanoparticles exhibit unique optical properties due to localized surface plasmon resonance (LSPR), which arises from the collective oscillation of conduction electrons in response to incident light. The optical properties of metal nanoparticles, such as absorption and scattering spectra, depend on factors like size, shape, composition, and surrounding medium.

Electronic Properties: The electronic structure of metal nanoparticles differs from bulk materials due to quantum confinement effects. Size-dependent electronic properties can lead to enhanced catalytic activity, tunable band gaps, and novel electronic behaviors, making metal nanoparticles promising for applications in electronics, sensors, and energy conversion.

Magnetic Properties: Some metal nanoparticles exhibit intrinsic magnetic properties, making them suitable for applications in data storage, magnetic resonance imaging (MRI), and magnetic hyperthermia therapy. Magnetic metal nanoparticles can be manipulated using external magnetic fields, offering opportunities for targeted drug delivery and magnetic separation processes.

Reactivity: The reactivity of metal nanoparticles can vary depending on their size, shape, and composition. Smaller nanoparticles often exhibit higher surface-to-volume ratios, leading to increased reactivity compared to larger particles. This enhanced reactivity can be utilized in catalysis, sensing, and environmental remediation applications.

Stability: The stability of metal nanoparticles is crucial for their practical applications. Factors such as surface passivation, capping agents, and environmental conditions can influence the stability of nanoparticles. Stable nanoparticles are essential for long-term storage, biomedical applications, and industrial processes.

Surface Plasmon Resonance (SPR): Surface plasmon resonance is a phenomenon observed in metal nanoparticles, where free electrons collectively oscillate in response to incident light, leading to enhanced absorption and scattering properties. The SPR characteristics of metal nanoparticles can be tuned by adjusting parameters such as size, shape, and surrounding medium, enabling applications in sensing, imaging, and photothermal therapy.

Assembly Structures: Metal nanoparticles can form various assembly structures such as clusters, superlattices, chains, or monolayers. These structures can exhibit unique properties and functionalities that differ from individual nanoparticles. Controlled assembly of metal nanoparticles is essential for applications in nanoelectronics, plasmonics, and metamaterials.

Surface Charge: The surface charge of metal nanoparticles, often determined by the presence of functional groups or ligands, plays a crucial role in their stability, dispersibility, and interactions with biological systems. Positively or negatively charged nanoparticles can influence cellular uptake, biodistribution, and toxicity profiles, impacting their use in biomedical and environmental applications.

Surface Roughness: Surface roughness of metal nanoparticles, characterized by irregularities or nanoscale features on their surfaces, can affect properties such as catalytic activity, optical response, and adhesion behavior. Tuning the surface roughness of nanoparticles through controlled synthesis or surface modifications can enhance their performance in various applications.

SPR Tunability: The surface plasmon resonance (SPR) of metal nanoparticles can be tuned by adjusting parameters such as size, shape, composition, and surrounding medium. Tunable SPR properties enable control over the absorption and scattering of light, making metal nanoparticles valuable for applications in sensing, imaging, and photothermal therapy.

Chirality: Chiral metal nanoparticles exhibit asymmetry in their structure, leading to unique optical properties and interactions with polarized light. Chiral nanoparticles can display enhanced circular dichroism, optical activity, and selective interactions with chiral molecules, offering opportunities in chiral sensing, catalysis, and photonics.

Core-Shell Structures: Metal nanoparticles can possess core-shell structures, where a core of one metal is surrounded by a shell of another material. Core-shell nanoparticles combine the properties of both materials, offering synergistic effects such as enhanced stability, catalytic activity, or magnetic behavior. Core-shell nanoparticles are utilized in catalysis, sensing, and biomedical applications.

Ligand Interactions: Metal nanoparticles can be functionalized with ligands such as organic molecules, polymers, or biomolecules to modify their surface properties, enhance stability, and enable specific interactions. Ligand-functionalized nanoparticles play a crucial role in applications like drug delivery, biosensing, and catalysis.

Plasmonic Coupling: When metal nanoparticles are in close proximity, their localized surface plasmon resonances can interact with each other, leading to plasmonic coupling effects. Plasmonic coupling results in new optical properties, such as redshifts in absorption spectra, enhanced electromagnetic fields, and improved sensitivity in plasmonic sensors.

Quantum Effects: At the nanoscale, metal nanoparticles exhibit quantum effects such as quantum confinement, size-dependent electronic structure, and discrete energy levels. Quantum effects can influence the optical, electronic, and catalytic properties of nanoparticles, offering unique opportunities for applications in quantum computing, photonics, and energy conversion.

Core Shell Structures: AI Notes

Examples: Core-Shell Nanoparticles, Core-Shell Catalysts, Core-Shell Polymers.

Core:

  • The core often provides the main functionality or desired property of the material. For example, in catalytic core-shell nanoparticles, the core material acts as the active site for catalysis.
  • The core can also determine the physical or chemical properties of the material, such as magnetic, optical, or electronic properties.
  • The core is responsible for the specific application of the material, such as drug delivery, sensing, or catalysis.

Shell:

  • The shell serves as a protective layer for the core, preventing its degradation, agglomeration, or unwanted interactions with the environment.
  • The shell can control the release rate of active components from the core, making core-shell structures useful in controlled drug delivery systems.
  • The shell can provide additional functionalities to the material, such as improving stability, biocompatibility, or dispersibility.

By combining different core and shell materials, researchers can tailor core-shell structures to meet specific requirements for a wide range of applications in fields like nanotechnology, catalysis, biomedicine, and materials science.

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