Nanomaterials Engineering: Applications and Properties

This video explains three key characterization techniques for nanomaterials: Scanning Electron Microscopy (SEM) uses an electron beam to scan specimen surfaces, detecting secondary electrons for topographical imaging with resolution up to 1 nm; Transmission Electron Microscopy (TEM) transmits electron beams through thin specimens to reveal internal structures at resolutions down to 0.1 nm; and Atomic Force Microscopy (AFM) measures atomic forces between a sharp tip and sample surface to generate 3D topographical images without requiring vacuum, making it suitable for insulating and biological samples.

Various techniques characterize nanomaterials: (1) SEM (Scanning Electron Microscopy) - shows surface morphology, (2) TEM (Transmission Electron Microscopy) - reveals internal structure, (3) AFM (Atomic Force Microscopy) - measures surface topology and roughness, (4) XRD (X-ray Diffraction) - determines crystallographic structure, (5) FTIR - identifies chemical bonds and molecular structure, (6) Raman Spectroscopy - reveals vibrational modes and composition, (7) UV-Vis Spectroscopy - studies optical properties and band gap, (8) TGA (Thermogravimetric Analysis) - measures thermal stability, (9) Zeta Potential - determines surface charge and colloidal stability, (10) XPS (X-ray Photoelectron Spectroscopy) - analyzes surface chemical composition.

Microscopy-based techniques are essential for morphological studies of nanoparticles, determining size and shape. Scanning Electron Microscopy (SEM) uses an electron beam to scan sample surfaces, providing 3D topographical images with large depth of field. Transmission Electron Microscopy (TEM) transmits electrons through thin samples for internal structure analysis. Atomic Force Microscopy (AFM) scans surfaces with atomic-scale probes, providing accurate size/shape measurements without mathematical treatment. Scanning Tunneling Microscopy (STM) uses quantum tunneling for atomic-resolution imaging. Energy Dispersive X-ray Spectroscopy (EDX) determines elemental composition by analyzing X-rays emitted when electron beams strike samples. High Resolution TEM (HRTEM) provides atomic-level crystallographic imaging.

Nanotechnology characterization instruments like scanning electron microscopes (SEM), transmission electron microscopes (TEM), scanning tunneling microscopes (STM), and atomic force microscopes (AFM) enable scientists to image, measure, and manipulate nanoscale structures by using electron beams, quantum tunneling effects, or atomic-scale tips to overcome the wavelength limitations of optical microscopes, which cannot resolve objects smaller than approximately 200 nanometers.

Electron microscopy techniques including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Scanning Probe Microscopy (SPM), Atomic Force Microscopy (AFM), and Scanning Tunneling Microscopy (STM) are essential tools for characterizing nanomaterials by examining their morphology and surface properties at the atomic level, with each technique utilizing different principles such as electron transmission, surface scanning, and quantum tunneling to achieve resolutions beyond what optical microscopy can provide.

Nanomedicine uses nanoparticles (1-10 nanometers, virus-sized) for targeted drug delivery, developed over 40-50 years. The goal is delivering medications specifically to target sites rather than distributing them generally, improving therapeutic ratios and reducing side effects. Nanoparticles face biological barriers: agglomeration causing embolisms, filtration by lungs and liver via Kupffer cells, and elimination by the reticuloendothelial system. Surface modification with hydrophilic polymers (PEG) creates stealth effects to avoid immune detection. Renal elimination creates trade-offs between particle size and therapeutic safety.

Nanomedicine for targeted drug delivery focuses on developing nanoparticles to enhance drug targeting and release for unmet medical needs, with most approved products being lipid-based formulations (12 out of 13 worldwide) utilizing either active loading technologies (creating concentration gradients for efficient drug loading) or passive loading technologies (direct drug association with carriers), though many academic researchers pursue increasingly complex multifunctional nanoparticles that may not translate clinically due to manufacturing challenges, whereas simpler approaches like combining two drugs in a single liposomal formulation at optimal ratios have demonstrated significant clinical success, as evidenced by Viccos (a liposomal combination therapy for AML acquired for $1.5 billion).

Upon intravenous administration, LNPs rapidly acquire a protein corona primarily composed of apolipoprotein E (ApoE), which binds to lipid surfaces and influences biodistribution. ApoE binding causes redistribution of LNP lipids: cholesterol increases at the surface while cationic lipid decreases at the surface and potentially increases in the core. This structural change reduces the number of cationic lipids available for endosomal membrane disruption, demonstrating that formulation-optimized structures may differ significantly from in vivo conditions. To address inflammatory responses limiting repeated dosing, anti-inflammatory prodrugs can be incorporated into LNP surfaces. Using SANS with deuterated compounds confirmed surface localization, enabling enzymatic cleavage before cellular entry. This functionalization strategy successfully created LNPs with reduced inflammatory profiles while maintaining therapeutic efficacy. Key principles for optimizing LNP design include understanding that transfection efficacy depends on both particle size and surface composition, not just size alone; considering how LNPs transform upon encountering biological environments; and using advanced characterization techniques like SANS to visualize dynamic structural changes. These principles apply broadly to nanomedicine development, where understanding the relationship between structure and function guides rational design of improved delivery systems.

Advanced nanoparticle drug delivery systems function like autonomous vehicles that can navigate through the bloodstream, cross biological barriers, identify specific target cells, attach to them, and release their therapeutic payloads at precisely controlled times. These systems integrate multiple functions—targeting, navigation, recognition, and release—into single nanoscale devices that operate independently within the body.

Modern nanomedicine employs various nanoparticle types including liposomes, nanospheres, core-shell particles, albumin-based nanoparticles, and dendritic polymers. These carriers store drugs internally and release them upon reaching targets. Particle surfaces are modified with functional molecules for targeting. Key targeting molecules include aptamers (oligonucleotide/peptide binders) and antibodies (Y-shaped immune proteins). Surface modifications enable nanoparticles to seek specific receptors, making targeted delivery possible for conditions like cancer, insulin delivery, Alzheimer's, and Parkinson's disease.

This section explores applications of 2D materials in next-generation electronic devices. For logic devices, 2D materials address short channel effects and mobility degradation that plague scaled-down Si MOSFETs. As Si channel thickness drops below 3 nm, mobility degrades due to quantum confinement, but 2D materials maintain atomic-scale thickness without mobility loss. RF devices leverage graphene's high mobility for cutoff frequencies exceeding 400 GHz, though graphene's zero band gap causes high output conductance that limits fmax. TMDs and black phosphorus offer finite band gaps with comparable fmax to graphene's fT, enabling power-efficient RF applications. Tunnel FETs overcome the 60 mV/decade subthreshold swing limit of conventional MOSFETs by utilizing band-to-band tunneling. PIN/INP configurations enable effective off-state blocking. Vertical TFET architectures provide larger tunneling areas than lateral devices. Black phosphorus TFETs show particularly high on-current due to direct band gap and high mobility. These diverse applications demonstrate how 2D materials can address specific performance requirements across different device regimes.

This section presents cutting-edge research on 2D materials and their application in advanced nanoelectronics. Two-dimensional materials with thickness below 10 nm offer revolutionary opportunities for electronics. While graphene (discovered 2004) is a semimetal unsuitable for digital circuits, transition metal dichalcogenides (TMDCs) serve as direct-gap semiconductors with ~2 eV bandgaps ideal for transistors. The research developed an analytical model for CMOS inverters using 2D TMDC transistors, deriving expressions for switching voltage and gain coefficient accounting for quasi-ballistic/ballistic transport and Drain-Induced Barrier Lowering (DIBL) effects. Key findings demonstrate that high gain coefficients enable fast switching and improved noise immunity, with unequal DIBL coefficients causing gain variation with K. This modeling framework enables prediction of inverter performance for designing next-generation nanoelectronic circuits.

Two-dimensional (2D) materials are just a few atoms thick yet display extraordinary control over electronic, optical, and mechanical behavior. Graphene is the best-known example, but transition metal dichalcogenides (TMDS) offer particularly exciting prospects as ultra-thin sandwiches with semiconducting properties. Unlike graphene's zero band gap, many TMDS monolayers exhibit sizable direct band gaps in the visible or near-infrared range, making them ideal for next-generation transistors, LEDs, photodetectors, and ultra-thin solar cells. Samsung demonstrated 200mm wafer-scale TMDS transistors in commercial semiconductor fabrication, closing the gap between lab and production.

2D materials like graphene and transition metal dichalcogenides (e.g., MoS2) offer promising alternatives to silicon for next-generation electronics, but face fundamental challenges including zero band gap in graphene (requiring band gap engineering through nanoribbons or bilayer structures), low mobility in MoS2, and power dissipation issues at nanoscale dimensions. Computational methods including density functional theory (DFT), GW approximation, and non-equilibrium Green's function (NEGF) are essential for predicting device performance and guiding fabrication strategies.

Two-dimensional (2D) materials are nanomaterials with only one dimension at the nanoscale (1-100 nm), offering unique properties such as high surface-to-volume ratios, absence of dangling bonds, and tunable electronic band gaps that make them superior to traditional thin films for electronic applications; these materials, including graphene (a 2D semimetal with zero band gap and exceptional electron mobility), transition metal dichalcogenides (TMDs), and other 2D compounds, can be synthesized through top-down methods like mechanical exfoliation or bottom-up approaches like chemical vapor deposition, and their ability to form vertical heterostructures with 0D, 1D, and 3D materials opens up promising applications in next-generation electronics, sensors, and optoelectronic devices.

Engineered nanomaterials are released to the natural environment during product manufacturing, use, and disposal, undergoing transformations such as aggregation, dissolution, and chemical reactions that alter their properties and potential toxicity; while human exposures in the environment are generally low compared to occupational settings, ecological risks remain uncertain due to limited environmental concentration measurements, with nanomaterials like silver, zerovalent iron, and zinc oxide showing the highest toxicity potential in aquatic and soil systems.

Scientists predict potential risks from nanomaterials: environmental risks include severe pollution from nanomaterial waste due to their small size and ability to penetrate cells; health risks include potential penetration of nanomaterials through skin and lungs, which could cause health problems.

Nanotoxicology is the scientific study of nanoparticle toxicity in humans and the environment, examining how nanoparticles' unique physicochemical properties—including high surface area to volume ratio, electrical and magnetic characteristics, and ability to penetrate biological barriers—can trigger cytotoxic and genotoxic responses through interactions with proteins, enzymes, and genetic material; nanoparticles enter the body via inhalation, ingestion, injection, and skin penetration, potentially causing dysfunction at cellular, subcellular, and protein levels, while environmental concerns include improper disposal leading to water and soil degradation, necessitating further research to develop structure-activity relationship models for predicting health and ecological impacts.

Contaminants impact organisms at all biological levels: individuals, populations, communities, and ecosystems. With approximately 75,000 chemicals registered for commercial use in the US, and only a small fraction having complete toxicity testing, comprehensive assessment is impossible through traditional testing alone. Nanoparticles add complexity because for any given substance, nanoparticles exist in many shapes and sizes with different properties, often coated or doped to achieve specific effects. This creates an overwhelming scale problem requiring alternative approaches beyond empirical testing.

Nanoparticles and nanomaterials present unique environmental health and safety challenges because they behave differently from conventional materials at the nanoscale. Current safety data sheets often provide inadequate information—for example, carbon nanotubes receive graphite-based safety data despite acting completely differently. Two illustrative cases highlight these concerns: (1) Washing machines containing silver nanoparticles designed to kill bacteria in wash water risk releasing these particles into sewage treatment systems and ultimately natural environments, potentially disrupting beneficial bacterial ecosystems; (2) European companies have developed face creams containing buckyballs (C60 molecules) as powerful antioxidants, but concerns exist about whether these particles can cross biological barriers like the blood-brain barrier. These examples demonstrate how nanomaterials can spread throughout ecosystems once released and why current regulatory frameworks are inadequate.