Basic Nanotechnology Engineering interview questions

150 questions with answers (NAN-001 to NAN-150). Try each one aloud before reading the answer.

Nanoscience Fundamentals

NAN-001 · What is the nanoscale?

The size range of roughly 1–100 nm in at least one dimension. One nanometre is 10⁻⁹ m, about the width of 3–4 atoms in a row.

NAN-002 · Why do material properties change at the nanoscale?

Two main reasons: the surface-to-volume ratio becomes very high, so surface atoms dominate behaviour, and quantum confinement alters electronic and optical states once dimensions approach the electron wavelength or exciton Bohr radius.

NAN-003 · Give examples of nanomaterials.

Carbon nanotubes, graphene, fullerenes, quantum dots, metal nanoparticles (Au, Ag), metal-oxide nanoparticles (TiO₂, ZnO), nanowires, dendrimers and liposomes.

NAN-004 · What are the main applications of nanotechnology?

Electronics and memory, targeted drug delivery and imaging, protective and self-cleaning coatings, chemical and biological sensors, catalysis, batteries and supercapacitors, solar cells and water purification.

NAN-005 · What is the difference between nanoscience and nanotechnology?

Nanoscience studies phenomena and properties of matter at the nanoscale. Nanotechnology applies that understanding to design, fabricate and use structures, devices and systems with controlled nanoscale features.

NAN-006 · Who is credited with first proposing the idea of nanotechnology?

Richard Feynman, in his 1959 lecture "There's Plenty of Room at the Bottom". Norio Taniguchi coined the term "nanotechnology" in 1974.

NAN-007 · How are nanomaterials classified by dimensionality?

0D: all dimensions nanoscale (nanoparticles, quantum dots). 1D: two dimensions nanoscale (nanotubes, nanowires). 2D: one dimension nanoscale (graphene, thin films). 3D: bulk materials built from nanoscale units (nanocomposites, nanoporous solids).

NAN-008 · What is surface-area-to-volume ratio and how does it scale for a sphere?

For a sphere, SA/V = 4πr² ÷ (4/3)πr³ = 3/r. Halving the radius doubles the ratio, so nanoparticles expose a large fraction of their atoms at the surface.

NAN-009 · What is surface energy?

The excess energy of atoms at a surface compared with the bulk, because surface atoms have fewer bonding neighbours. It is expressed in J/m² and drives agglomeration, sintering and reactivity of nanoparticles.

NAN-010 · What is a nanocomposite?

A multiphase material in which at least one phase has nanoscale dimensions, such as clay platelets or CNTs dispersed in a polymer, giving improved strength, barrier or conductive properties at low filler loading.

NAN-011 · What is a nanostructured material?

A material whose internal structure, such as grain size, pore size or layer thickness, is controlled at the nanoscale. Nanocrystalline metals with grains below 100 nm are a common example.

NAN-012 · Name some naturally occurring nanostructures.

Gecko foot setae, lotus-leaf surface texture, butterfly-wing photonic crystals, DNA (about 2 nm wide), proteins, viruses, clay minerals and volcanic ash particles.

NAN-013 · What is the role of van der Waals forces at the nanoscale?

They are weak, short-range attractions between all atoms and molecules. At the nanoscale they become dominant relative to gravity and inertia, causing particle agglomeration, stiction and adhesion, as in gecko feet.

Quantum & Size Effects

NAN-014 · What is quantum confinement?

When a material's size approaches the de Broglie wavelength of its charge carriers, their motion is restricted and energy levels become discrete rather than continuous bands, widening the effective bandgap.

NAN-015 · What is the exciton Bohr radius?

The natural separation of the electron and hole in a bound exciton in a given semiconductor. Strong confinement occurs when particle size is smaller than this radius, for example about 5–6 nm for CdSe.

NAN-016 · What is a quantum well, quantum wire and quantum dot?

A quantum well confines carriers in one dimension (2D free motion), a quantum wire in two dimensions (1D free motion) and a quantum dot in all three dimensions (0D, fully discrete levels).

NAN-017 · What is quantum tunnelling?

A quantum effect in which a particle passes through a potential barrier higher than its energy. Tunnelling probability falls exponentially with barrier width, so it becomes significant for barriers of a few nanometres.

NAN-018 · What is the de Broglie wavelength?

The wavelength associated with a moving particle, λ = h/p, where h is Planck's constant (6.626 × 10⁻³⁴ J·s) and p is momentum. For electrons in semiconductors it is typically a few to tens of nanometres.

NAN-019 · What is the density of states?

The number of available electron states per unit energy per unit volume. It varies as √E in 3D, is constant (step-like) in 2D, varies as 1/√E in 1D and becomes delta functions in 0D.

NAN-020 · Why does melting point drop for small nanoparticles?

Surface atoms are less strongly bound than interior atoms. As size falls, the surface fraction rises, so less thermal energy is needed to melt the particle. Gold nanoparticles of a few nm melt hundreds of degrees below bulk gold.

NAN-021 · What is a surface plasmon?

A collective oscillation of conduction electrons at a metal surface. In metal nanoparticles it becomes a localized surface plasmon resonance that strongly absorbs and scatters light at specific wavelengths.

NAN-022 · What is superparamagnetism?

In ferromagnetic nanoparticles small enough to be single-domain, thermal energy can flip the magnetization randomly. With no field the net moment averages to zero, but the particles magnetize strongly in an applied field with no remanence.

NAN-023 · What is Coulomb blockade?

Suppression of electron tunnelling onto a very small island because adding one electron raises its energy by the charging energy e²/2C. It is observed when this energy exceeds thermal energy kT.

NAN-024 · What is ballistic transport?

Electron transport in which carriers travel through a conductor without scattering, because the conductor is shorter than the mean free path. Resistance then arises from the contacts, not the channel.

NAN-025 · What is the quantum of conductance?

G₀ = 2e²/h ≈ 77.5 µS, corresponding to a resistance of about 12.9 kΩ. It is the conductance of one spin-degenerate ballistic channel.

NAN-026 · Why do nanoparticles show different colours from bulk material?

Size changes how they interact with light: metal nanoparticles show size-dependent plasmon resonances, and semiconductor nanocrystals show size-dependent bandgaps from quantum confinement, both shifting absorption and emission wavelengths.

Top-Down Fabrication & Lithography

NAN-027 · What is the difference between top-down and bottom-up fabrication?

Top-down carves or patterns bulk material down to nanoscale features using lithography, etching or milling. Bottom-up builds structures from atoms or molecules using CVD, sol-gel, colloidal synthesis or self-assembly.

NAN-028 · What is photolithography?

A patterning process in which light passes through a mask to expose a photosensitive resist on a substrate. The developed resist then serves as a mask for etching, deposition or implantation.

NAN-029 · What is a photoresist?

A light-sensitive polymer coating. In a positive resist the exposed areas become soluble in the developer; in a negative resist the exposed areas cross-link and become insoluble.

NAN-030 · What is electron-beam lithography?

A maskless technique that writes patterns directly in an electron-sensitive resist, such as PMMA, with a focused electron beam. It can achieve sub-10 nm features but is slow because it writes serially.

NAN-031 · What is wet etching?

Removal of material by liquid chemicals, such as HF for SiO₂ or KOH for silicon. It is usually isotropic, cheap and selective, but undercuts the mask, limiting fine features.

NAN-032 · What is dry etching?

Material removal using plasma or ions instead of liquids. Reactive ion etching (RIE) combines chemical reaction and ion bombardment to give anisotropic, vertical profiles needed for nanoscale features.

NAN-033 · What is focused ion beam (FIB) milling?

A technique that uses a finely focused beam of ions, typically Ga⁺, to sputter material locally. It is used for direct nanopatterning, circuit editing and preparing TEM lamellae.

NAN-034 · What is nanoimprint lithography?

A method that presses a patterned mould into a resist, then cures it thermally or with UV light, replicating nanoscale features mechanically. It offers high resolution at low cost per wafer.

NAN-035 · What is EUV lithography?

Extreme ultraviolet lithography uses 13.5 nm light, reflective multilayer mirrors and masks in vacuum to print the smallest features in leading-edge chip manufacturing.

NAN-036 · What is a cleanroom and why is it needed?

A controlled environment with very low airborne particle counts, controlled temperature and humidity. Even a single dust particle can be larger than nanoscale features and ruin a device.

NAN-037 · What is physical vapour deposition (PVD)?

Thin-film deposition in which material is physically vaporized by evaporation or sputtering in vacuum and condenses on a substrate, without a chemical reaction.

NAN-038 · What is ball milling?

A top-down mechanical method that grinds powders with hard balls in a rotating or vibrating jar, reducing particle size to the nanoscale and enabling mechanical alloying.

NAN-039 · What is a lift-off process?

A patterning method in which a material is deposited over a patterned resist, then the resist is dissolved, removing the material on top and leaving it only where the resist was open.

Bottom-Up Synthesis

NAN-040 · What is the sol-gel process?

A wet-chemical route in which metal alkoxide or salt precursors hydrolyse and condense to form a colloidal sol, which then links into a gel network. Drying and calcination give oxide nanoparticles, films or aerogels.

NAN-041 · What is a precursor in nanomaterial synthesis?

The starting compound that supplies the atoms of the final material, such as HAuCl₄ for gold nanoparticles, tetraethyl orthosilicate (TEOS) for silica or methane for graphene. Its reactivity largely sets nucleation and growth kinetics.

NAN-042 · What is template-assisted synthesis?

Growing nanostructures inside or on a pre-shaped template, such as the pores of anodic alumina or polycarbonate membranes, then removing the template. It yields nanowires and nanotubes of controlled diameter.

NAN-043 · What is a self-assembled monolayer (SAM)?

A single ordered layer of molecules that forms spontaneously on a surface, such as alkanethiols on gold. SAMs are used to control wetting, adhesion and biofunctionalization.

NAN-044 · What is colloidal synthesis?

Growth of nanoparticles in solution by chemical reduction or decomposition of precursors in the presence of stabilizing ligands, which control size and prevent aggregation.

NAN-045 · What is the Turkevich method?

A classic gold nanoparticle synthesis in which HAuCl₄ is reduced by sodium citrate in boiling water. Citrate acts as both reducing agent and stabilizer, producing particles of roughly 10–20 nm.

NAN-046 · What is atomic layer deposition (ALD)?

A thin-film technique that uses alternating, self-limiting surface reactions of two precursors, depositing one atomic layer per cycle. It gives excellent thickness control and conformal coatings.

NAN-047 · What is hydrothermal synthesis?

Crystallization of materials from aqueous solution at elevated temperature and pressure in a sealed autoclave. It is widely used for oxide nanoparticles, nanorods and zeolites.

NAN-048 · What is molecular beam epitaxy (MBE)?

Ultra-high-vacuum growth in which beams of atoms or molecules strike a heated crystalline substrate, building epitaxial layers one atomic layer at a time with precise control of composition.

NAN-049 · What is a capping agent or ligand in nanoparticle synthesis?

A molecule that binds to the nanoparticle surface to control growth, prevent aggregation and set solubility. Examples include citrate, oleic acid, oleylamine, thiols and PVP.

NAN-050 · What is the difference between nucleation and growth?

Nucleation forms new stable clusters from a supersaturated solution or vapour. Growth enlarges existing nuclei by adding atoms. Separating the two steps in time gives narrow size distributions.

NAN-051 · What is green synthesis of nanoparticles?

Synthesis using benign reagents such as plant extracts, microorganisms or sugars as reducing and capping agents, avoiding toxic chemicals and harsh conditions.

NAN-052 · What is electrospinning?

A process that uses a high voltage to draw a charged polymer solution into ultrafine fibres, typically tens to hundreds of nanometres in diameter, collected as a nonwoven mat.

Carbon Nanomaterials (CNT, Graphene, Fullerenes)

NAN-053 · What is graphene?

A single layer of sp²-bonded carbon atoms arranged in a two-dimensional hexagonal (honeycomb) lattice. It was first isolated by Geim and Novoselov in 2004 using mechanical exfoliation.

NAN-054 · What is a carbon nanotube?

A cylinder formed by rolling up a graphene sheet, with diameters from about 1 nm to tens of nm and lengths up to millimetres or more. It has very high strength and electrical and thermal conductivity.

NAN-055 · What is a fullerene?

A closed-cage carbon molecule made of pentagons and hexagons. The best known is C₆₀ (buckminsterfullerene), a truncated-icosahedron with 12 pentagons and 20 hexagons, discovered in 1985.

NAN-056 · How is graphite related to graphene?

Graphite is a stack of graphene layers held together by weak van der Waals forces, with an interlayer spacing of about 0.335 nm. Separating a single layer from graphite gives graphene.

NAN-057 · What hybridization does carbon have in graphene and diamond?

Graphene is sp² hybridized, with three in-plane σ bonds and a delocalized π electron. Diamond is sp³ hybridized, with four tetrahedral σ bonds.

NAN-058 · What is graphene oxide?

Graphene functionalized with oxygen groups such as hydroxyl, epoxy and carboxyl. It disperses in water and is electrically insulating; chemical or thermal reduction gives partly conductive reduced graphene oxide (rGO).

NAN-059 · What is the mechanical exfoliation ("Scotch tape") method?

Repeatedly peeling graphite with adhesive tape to cleave it into thinner flakes until single layers remain, then transferring them to a substrate. It gives high-quality graphene but is not scalable.

NAN-060 · What is the C–C bond length in graphene?

About 0.142 nm. The lattice constant of the hexagonal lattice is about 0.246 nm.

NAN-061 · What are carbon nanotubes used for?

Conductive additives in battery electrodes, composites for strength, transparent conductive films, field emitters, sensors, thermal interface materials and experimental transistors.

NAN-062 · What is a carbon quantum dot?

A small carbon nanoparticle, typically below 10 nm, with surface passivation that gives fluorescence. It is studied as a lower-toxicity alternative to heavy-metal quantum dots for imaging and sensing.

NAN-063 · What is the arc-discharge method?

A CNT and fullerene synthesis method that strikes a high-current arc between graphite electrodes in an inert gas. Carbon vaporizes and condenses; metal catalysts in the anode favour SWCNTs.

NAN-064 · What is an allotrope of carbon? Name some.

A different structural form of the same element. Carbon allotropes include diamond, graphite, graphene, carbon nanotubes, fullerenes and amorphous carbon.

NAN-065 · What is a graphene nanoribbon?

A narrow strip of graphene, typically below 50 nm wide. Its edge type (armchair or zigzag) and width govern its electronic properties, and narrow ribbons can open a bandgap.

Nanoparticles & Quantum Dots

NAN-066 · What is a nanoparticle?

A particle with all three external dimensions in the nanoscale, roughly 1–100 nm. Examples include gold, silver, silica, iron oxide and titanium dioxide nanoparticles.

NAN-067 · What is a quantum dot?

A semiconductor nanocrystal, typically 2–10 nm, small enough that quantum confinement makes its bandgap and emission colour depend on size. Common examples are CdSe, InP and PbS.

NAN-068 · What is a core-shell nanoparticle?

A particle with a core of one material coated with a shell of another, such as CdSe/ZnS. The shell passivates surface defects, improves stability and quantum yield, or adds functionality.

NAN-069 · Why are silver nanoparticles used in consumer products?

They release Ag⁺ ions that are antimicrobial, so they are added to wound dressings, textiles, coatings and food-contact surfaces.

NAN-070 · What are magnetic nanoparticles used for?

Iron oxide nanoparticles (magnetite Fe₃O₄, maghemite γ-Fe₂O₃) are used as MRI contrast agents, for magnetic separation, hyperthermia cancer therapy and targeted drug delivery.

NAN-071 · What is a dendrimer?

A highly branched, tree-like synthetic polymer with a central core, repeating generations of branches and many surface groups. Its precise size and multivalent surface suit drug and gene delivery.

NAN-072 · What is the quantum yield of a quantum dot?

The ratio of photons emitted to photons absorbed. Well-passivated core-shell quantum dots can exceed 80–90%.

NAN-073 · What is a nanowire?

A one-dimensional structure with a diameter of a few to tens of nanometres and length much greater, made of metals, semiconductors (Si, ZnO, GaN) or oxides.

NAN-074 · What is the difference between agglomeration and aggregation?

Agglomerates are loosely bound clusters held by weak forces that can be redispersed. Aggregates are strongly bonded or fused particles that are hard to separate.

NAN-075 · What is polydispersity?

The spread of particle sizes in a sample. A monodisperse sample has a narrow size distribution, often specified as less than about 5–10% standard deviation of diameter.

NAN-076 · What are titanium dioxide nanoparticles used for?

UV-blocking sunscreens, photocatalytic self-cleaning surfaces, air and water purification, pigments and dye-sensitized solar cells. Anatase is usually the more photocatalytically active phase.

NAN-077 · What is a nanoshell?

A spherical particle with a dielectric core, such as silica, and a thin metal shell, usually gold. Tuning the core-to-shell ratio shifts the plasmon resonance into the near-infrared.

NAN-078 · What are quantum dots used for?

Display backlights and colour conversion, biological imaging and labelling, LEDs, photodetectors, solar cells and single-photon sources.

Characterization Techniques

NAN-079 · What is a scanning electron microscope (SEM)?

An instrument that scans a focused electron beam over a sample and detects secondary and backscattered electrons to image surface topography and composition, with resolution down to about 1 nm.

NAN-080 · What is a transmission electron microscope (TEM)?

A microscope that passes high-energy electrons through a very thin sample (typically under 100 nm thick) to image internal structure, crystal lattices and defects, reaching sub-ångström resolution in aberration-corrected instruments.

NAN-081 · What is atomic force microscopy (AFM)?

A scanning probe technique in which a sharp tip on a cantilever senses forces from the surface. Cantilever deflection, read by a laser, maps topography with sub-nanometre vertical resolution on conductors and insulators.

NAN-082 · What is scanning tunnelling microscopy (STM)?

A technique that scans a sharp metal tip a few ångströms above a conductive surface and measures the tunnelling current. Because current depends exponentially on gap, it achieves atomic resolution.

NAN-083 · What is X-ray diffraction (XRD) used for?

Identifying crystal phases, measuring lattice parameters, strain and estimating crystallite size from peak broadening, based on Bragg's law nλ = 2d sinθ.

NAN-084 · What is dynamic light scattering (DLS)?

A technique that measures fluctuations in scattered laser light caused by Brownian motion of particles in suspension. It gives the hydrodynamic diameter via the Stokes-Einstein equation.

NAN-085 · What is Raman spectroscopy?

A technique that measures inelastic scattering of monochromatic light, revealing vibrational modes. It is widely used to identify carbon nanomaterials and count graphene layers.

NAN-086 · What is UV-Vis spectroscopy used for in nanotechnology?

Measuring optical absorption to track plasmon resonances of metal nanoparticles, estimate quantum dot size from the first exciton peak, and determine concentration using Beer-Lambert law.

NAN-087 · What is BET surface area analysis?

A gas adsorption method, usually with N₂ at 77 K, that applies the Brunauer-Emmett-Teller model to measure the specific surface area of powders and porous materials in m²/g.

NAN-088 · What is energy-dispersive X-ray spectroscopy (EDS/EDX)?

An elemental analysis technique, usually attached to SEM or TEM, that detects characteristic X-rays emitted when the electron beam ionizes inner-shell electrons, giving composition and elemental maps.

NAN-089 · What is X-ray photoelectron spectroscopy (XPS)?

A surface-sensitive technique that irradiates a sample with X-rays and measures emitted photoelectron energies, giving elemental composition and chemical states from the top few nanometres.

NAN-090 · What is zeta potential?

The electric potential at the slipping plane of a particle in suspension, measured from electrophoretic mobility. Magnitudes above about 30 mV typically indicate good electrostatic colloidal stability.

Nanoelectronics & Spintronics

NAN-091 · What is nanoelectronics?

Electronics using components with critical dimensions at the nanoscale, where quantum effects, tunnelling and atomistic variability matter. It includes modern CMOS transistors, molecular electronics and nanowire devices.

NAN-092 · What is Moore's law?

Gordon Moore's 1965 observation, revised in 1975, that the number of transistors on an integrated circuit doubles roughly every two years.

NAN-093 · What is spintronics?

Electronics that uses the electron's spin, as well as its charge, to store and process information. Hard-disk read heads and MRAM are commercial spintronic devices.

NAN-094 · What is giant magnetoresistance (GMR)?

A large change in electrical resistance of a ferromagnet/non-magnet/ferromagnet multilayer depending on whether the layer magnetizations are parallel (low resistance) or antiparallel (high resistance). Fert and Grünberg won the 2007 Nobel Prize for it.

NAN-095 · What is tunnelling magnetoresistance (TMR)?

The change in tunnelling resistance across a thin insulating barrier between two ferromagnets, depending on their relative magnetization. Magnetic tunnel junctions with MgO barriers show large TMR ratios.

NAN-096 · What is a FinFET?

A multi-gate transistor in which the channel is a thin vertical fin wrapped by the gate on three sides, improving electrostatic control and reducing short-channel effects compared with planar MOSFETs.

NAN-097 · What is a gate-all-around (GAA) transistor?

A transistor in which the gate completely surrounds the channel, usually stacked nanosheets or nanowires, giving the best electrostatic control. It succeeds FinFETs at the most advanced nodes.

NAN-098 · What is a single-electron transistor (SET)?

A device in which a small conducting island is connected to source and drain by tunnel junctions and controlled by a gate. Coulomb blockade lets electrons pass one at a time.

NAN-099 · What is molecular electronics?

The use of single molecules or molecular layers as active electronic components, such as wires, rectifiers or switches, between nanoscale electrodes.

NAN-100 · What is MRAM?

Magnetoresistive random-access memory stores bits in the magnetization of magnetic tunnel junctions. It is non-volatile, fast and has high endurance.

NAN-101 · What is a memristor?

A two-terminal device whose resistance depends on the history of current through it and is retained without power. It is used in resistive RAM and neuromorphic computing.

NAN-102 · What is a short-channel effect?

Degradation of transistor behaviour when channel length becomes comparable to depletion widths, including threshold voltage roll-off, drain-induced barrier lowering and increased leakage.

MEMS & NEMS

NAN-103 · What is MEMS?

Micro-electro-mechanical systems: devices that integrate mechanical structures, sensors, actuators and electronics on a chip, with features from about 1 µm to 1 mm. Examples are accelerometers, gyroscopes and microphones.

NAN-104 · What is NEMS?

Nano-electro-mechanical systems: electromechanical devices with critical dimensions below about 100 nm, such as nanobeam resonators and nanowire sensors, offering very high frequency and mass sensitivity.

NAN-105 · What is bulk micromachining?

Fabrication of MEMS by selectively etching into the bulk substrate, often silicon with KOH or deep reactive ion etching, to form cavities, membranes and beams.

NAN-106 · What is surface micromachining?

Building MEMS from thin films deposited on a substrate, using a sacrificial layer (often SiO₂) that is later etched away to release movable structures such as polysilicon beams.

NAN-107 · What is a cantilever?

A beam fixed at one end and free at the other. In MEMS and AFM, its deflection or resonant frequency shift senses force, mass or surface stress.

NAN-108 · What is a MEMS accelerometer?

A sensor with a proof mass suspended by springs. Acceleration displaces the mass, and the displacement is measured, usually capacitively, giving an output proportional to acceleration.

NAN-109 · What is a MEMS gyroscope?

A sensor with a vibrating proof mass. Rotation produces a Coriolis force perpendicular to the drive motion, and the resulting sense-mode displacement gives the angular rate.

NAN-110 · What is stiction in MEMS?

Permanent adhesion of movable microstructures to the substrate or each other due to capillary, van der Waals or electrostatic forces, often occurring during wet release.

NAN-111 · What is deep reactive ion etching (DRIE)?

A high-aspect-ratio silicon etch, commonly the Bosch process, that alternates SF₆ etching with C₄F₈ passivation to produce near-vertical sidewalls hundreds of micrometres deep.

NAN-112 · What is a sacrificial layer?

A temporary layer deposited under a structural layer and later removed by selective etching to free the structure, such as SiO₂ under polysilicon removed with HF.

NAN-113 · Name common MEMS actuation methods.

Electrostatic, piezoelectric, thermal (bimorph or electrothermal), magnetic and shape-memory alloy actuation.

NAN-114 · Where are MEMS devices used?

Smartphones (accelerometers, gyroscopes, microphones), automotive airbags and tyre pressure sensors, inkjet print heads, digital micromirror projectors, RF switches and medical pressure sensors.

Nanomedicine & Drug Delivery

NAN-115 · What is nanomedicine?

The application of nanotechnology to medicine, including nanoscale drug carriers, imaging contrast agents, diagnostics, theranostics and regenerative scaffolds.

NAN-116 · What is a liposome?

A spherical vesicle with one or more phospholipid bilayers enclosing an aqueous core. It can carry water-soluble drugs inside and lipophilic drugs in the bilayer. Doxil is a liposomal doxorubicin.

NAN-117 · What is a lipid nanoparticle (LNP)?

A nanoparticle of ionizable lipids, helper lipids, cholesterol and PEG-lipids that encapsulates nucleic acids. LNPs deliver the mRNA in COVID-19 vaccines and siRNA therapeutics.

NAN-118 · What is the EPR effect?

The enhanced permeability and retention effect: leaky tumour blood vessels let nanoparticles escape into tumour tissue, and poor lymphatic drainage retains them, giving passive accumulation.

NAN-119 · What is passive versus active targeting?

Passive targeting relies on size and circulation behaviour, such as the EPR effect. Active targeting attaches ligands such as antibodies, peptides or folate that bind receptors on target cells.

NAN-120 · What is PEGylation?

Attaching polyethylene glycol chains to a nanoparticle or drug. It forms a hydrated layer that reduces protein adsorption and immune clearance, extending circulation time.

NAN-121 · What is a polymeric nanoparticle?

A drug carrier made of biodegradable polymers such as PLGA, PLA or chitosan, which encapsulate or bind drugs and release them as the polymer degrades or swells.

NAN-122 · What is theranostics?

Combining therapy and diagnostics in one agent, such as a nanoparticle that both images a tumour and delivers a drug or heat to it.

NAN-123 · What is photothermal therapy?

A treatment in which nanoparticles, such as gold nanorods or nanoshells, absorb near-infrared light and convert it to heat, locally killing cancer cells.

NAN-124 · What is a polymeric micelle?

A core-shell structure formed by amphiphilic block copolymers in water, with a hydrophobic core that carries poorly soluble drugs and a hydrophilic shell that stabilizes it.

NAN-125 · What is the protein corona?

The layer of proteins that adsorbs onto a nanoparticle in biological fluids. It changes the particle's identity, affecting uptake, biodistribution, targeting and toxicity.

NAN-126 · What is controlled release?

Delivery of a drug at a defined rate or in response to a trigger such as pH, temperature, enzymes or light, maintaining therapeutic levels while reducing side effects.

Nanotech for Energy & Environment

NAN-127 · How is nanotechnology used in lithium-ion batteries?

Nanostructured electrodes shorten ion diffusion paths, increasing rate capability. Nano-silicon anodes, carbon nanotube conductive additives and nanoscale coatings improve capacity and cycle life.

NAN-128 · What is a supercapacitor?

An electrochemical capacitor storing charge in the electrical double layer or by fast surface redox reactions. High-surface-area nanocarbons give high power density and long cycle life.

NAN-129 · What is photocatalysis?

Using light-absorbing semiconductors such as TiO₂ to generate electron-hole pairs that drive chemical reactions, including degrading pollutants and splitting water.

NAN-130 · How do nanomaterials improve catalysis?

High surface area exposes more active sites, and small particles have more edge and corner atoms with distinct reactivity. Supported Pt, Pd and Au nanoparticles are widely used.

NAN-131 · What is a quantum dot solar cell?

A photovoltaic device that uses quantum dots, such as PbS, as the light absorber. Their bandgap can be tuned by size and they can be solution-processed.

NAN-132 · What is a dye-sensitized solar cell?

A solar cell in which dye molecules adsorbed on a mesoporous TiO₂ nanoparticle film absorb light and inject electrons into the TiO₂, with a redox electrolyte regenerating the dye.

NAN-133 · How is nanotechnology used in water purification?

Nanofiltration membranes, adsorbent nanomaterials, photocatalytic nanoparticles, antimicrobial silver nanoparticles and nanoscale zero-valent iron for contaminant reduction.

NAN-134 · What is nanoscale zero-valent iron (nZVI)?

Iron nanoparticles used in groundwater remediation to chemically reduce contaminants such as chlorinated solvents, Cr(VI) and nitrates.

NAN-135 · What is a nanoporous material?

A material with pores in the nanoscale range, such as zeolites, mesoporous silica, activated carbon and metal-organic frameworks, used for adsorption, separation and catalysis.

NAN-136 · What is a metal-organic framework (MOF)?

A crystalline porous material made of metal ions or clusters linked by organic ligands. MOFs have very high surface areas and are studied for gas storage, carbon capture and catalysis.

NAN-137 · What is a thermoelectric material?

A material that converts a temperature difference to voltage (Seebeck effect) or vice versa. Nanostructuring reduces thermal conductivity by scattering phonons, improving efficiency.

NAN-138 · What is an aerogel?

An ultralight solid made by replacing a gel's liquid with gas without collapsing its nanoporous network, giving very low density and thermal conductivity. Silica aerogels are used as insulation.

Nanotoxicology, Safety & Ethics

NAN-139 · What is nanotoxicology?

The study of the adverse effects of nanomaterials on living organisms and the environment, including exposure routes, mechanisms such as oxidative stress, and dose-response.

NAN-140 · What are the main exposure routes for nanomaterials?

Inhalation, skin contact, ingestion and injection. Inhalation is usually the main occupational concern.

NAN-141 · What is oxidative stress?

An imbalance in which reactive oxygen species exceed the cell's antioxidant defences, damaging lipids, proteins and DNA. It is a key mechanism of nanoparticle toxicity.

NAN-142 · What PPE is used when handling nanopowders?

Nitrile gloves, lab coats, safety glasses and respirators with high-efficiency filters (such as N95/FFP2 or better) where airborne exposure is possible, alongside engineering controls such as fume hoods.

NAN-143 · What is the hierarchy of controls?

A ranking of risk controls: elimination, substitution, engineering controls, administrative controls and finally PPE. For nanomaterials, handling in slurries and in ventilated enclosures is preferred over relying on respirators.

NAN-144 · Why is dose expressed differently for nanoparticles?

Toxicity often correlates better with surface area or particle number than with mass, because small particles have far more surface per gram. Mass alone can understate the dose.

NAN-145 · What is a safety data sheet (SDS)?

A document describing a chemical's hazards, safe handling, storage, PPE, first aid and disposal. Nanoform SDSs should note particle size and form, which may not appear for bulk material.

NAN-146 · What is the precautionary principle?

The principle that, when an activity raises plausible threats of harm, protective measures should be taken even if cause and effect are not fully established scientifically.

NAN-147 · What is "safe-by-design"?

An approach that builds safety into a nanomaterial or product early in development, for example choosing less toxic compositions, coatings or forms that reduce release.

NAN-148 · What are ethical concerns in nanotechnology?

Unknown health and environmental risks, privacy with nanosensors, equitable access, human enhancement, military uses, informed consent in trials and transparent labelling.

NAN-149 · What is the grey goo scenario?

A hypothetical scenario, popularized by Eric Drexler, in which self-replicating nanorobots consume all matter. It is widely considered implausible but raised early public concern.

NAN-150 · What is life cycle assessment (LCA) for nanoproducts?

An evaluation of environmental impacts across a product's life, from raw material extraction and synthesis through use to disposal, including possible nanomaterial release at each stage.

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