Applications of nanotechnology: medicine, electronics and energy

In short

Nanotechnology becomes useful at the point where a nanoscale property — huge specific surface area, tunable band gap, quantum tunnelling, single-domain magnetism, cell-scale dimensions — is converted into a device or a dose. The three biggest application blocks examined in Indian B.Tech curricula are medicine (drug delivery, imaging, diagnostics), electronics (CMOS scaling, memory, displays, sensors) and energy (batteries, supercapacitors, solar cells, fuel cells, catalysis). This topic carries direct marks in nanotechnology, materials and "emerging technologies" papers and in GATE-MT/NT style questions, and is the most interview-friendly part of the subject because it is where numbers, standards and products live. In India it is backed by the DST Nano Mission, the India Semiconductor Mission, the PLI for advanced chemistry cells and the National Green Hydrogen Mission, and regulated for medicines by CDSCO.

Explained

Why the nanoscale changes an application

• Surface area per gram explodes: a sphere has A/V = 6/d, so cutting size from 1 µm to 10 nm multiplies specific surface area 100×. This is what makes nanocatalysts, electrodes and adsorbents work.
• Faster dissolution: by Noyes–Whitney, dissolution rate ∝ surface area, so nanosizing a poorly soluble drug raises bioavailability without changing its chemistry (nanocrystal formulations).
• Size matched to biology: 10–200 nm carriers circulate, cross leaky tumour vasculature and are taken up by cells; below ~6 nm hydrodynamic diameter they are cleared by the kidney.
• Quantum/band-structure effects: confinement shifts the band gap (quantum-dot colour), and tunnelling through a few-nanometre oxide sets the limit of transistor and flash-memory scaling.
• Single-domain magnetism and superparamagnetism: iron-oxide particles below ~20 nm magnetise strongly but retain no remanence — used for MRI contrast, separation and hyperthermia.
• Limitation common to all three sectors: nanoscale advantages come with agglomeration, high cost of controlled synthesis, batch-to-batch variability and toxicity/EHS questions.

Medicine: delivery, imaging and diagnostics

• Goal of nano drug delivery: raise the fraction of dose reaching the target, lower the fraction reaching healthy tissue — i.e. widen the therapeutic index, not increase potency.
• Carrier families:
  • Liposomes — phospholipid bilayer vesicles, 50–200 nm; carry water-soluble drug in the core and lipophilic drug in the bilayer. Doxorubicin liposomes (PEGylated, "stealth") cut cardiotoxicity; amphotericin-B liposomes cut nephrotoxicity. Indian firms (Sun Pharma, Cipla, Zydus, Bharat Serums, Intas) market liposomal and nanosuspension products.
  • Lipid nanoparticles (LNP) — ionisable lipid + cholesterol + helper lipid + PEG-lipid; the delivery vehicle that made mRNA vaccines possible, including Gennova's indigenously developed mRNA COVID-19 vaccine.
  • Polymeric nanoparticles — PLGA, PLA, chitosan; biodegradable, give sustained release over days to weeks.
  • Dendrimers — branched, monodisperse polymers (PAMAM) with a defined number of surface groups per generation; high drug/ligand loading but cationic surfaces can be cytotoxic.
  • Micelles — self-assembled amphiphilic blocks above the critical micelle concentration; solubilise hydrophobic drugs (paclitaxel).
  • Inorganic — gold nanoparticles/nanorods (photothermal therapy, lateral-flow test lines), mesoporous silica (high-capacity pores), iron oxide (MRI, hyperthermia), quantum dots (fluorescent labels, limited clinically by cadmium toxicity).
• Targeting:
  • Passive — the EPR effect: leaky tumour capillaries and poor lymphatic drainage accumulate 10–200 nm particles. Real but highly variable between tumours; modern literature treats EPR as modest in humans.
  • Active — ligands (folate, transferrin, antibodies, peptides) on the surface bind receptors over-expressed on target cells.
  • Stimulus-responsive — release triggered by tumour/endosomal pH, redox (glutathione), enzymes, temperature or an external magnetic/ultrasound field.
• Overcoming the biological barriers: opsonins adsorb within seconds and the mononuclear phagocyte system clears particles from the liver and spleen; PEGylation ("stealth" coating) slows this. Surface charge, shape and the protein corona often matter more than the chemistry chosen on paper.
• Imaging and theranostics: superparamagnetic iron oxide as a T2 MRI agent; gold for CT/photoacoustic contrast; quantum dots and upconversion particles for optical imaging; "theranostic" particles carry drug plus label in one construct.
• Diagnostics: gold-nanoparticle lateral-flow rapid tests (the familiar red line), nanoparticle-amplified ELISA, DNA-functionalised colorimetric assays, nano-biosensors with CNT/graphene FET channels, lab-on-chip. India's wide use of rapid antigen and pregnancy test strips is nanoparticle immunoassay at scale.
• Other therapies: magnetic hyperthermia, photothermal and photodynamic therapy, silver-nanoparticle antimicrobial dressings, nano-hydroxyapatite in bone cements and toothpastes, nanofibre tissue-engineering scaffolds (electrospun PCL/collagen).
• Indian regulation and standards:
  • A nanopharmaceutical is approved as a new drug under the New Drugs and Clinical Trials Rules, 2019 (Drugs and Cosmetics Act, 1940); CDSCO's Guidelines for Evaluation of Nanopharmaceuticals in India (2019) set the extra data needed — size and size distribution, zeta potential, surface chemistry, in-vitro release, stability, and demonstration that a nano version is *not* automatically bioequivalent to the conventional one.
  • Quality standards follow the Indian Pharmacopoeia 2026 (10th edition); cosmetics with nanomaterials fall under the Cosmetics Rules, 2020; food applications under FSSAI; agri-inputs under DBT/ICAR guidance.
  • Workplace exposure to nanopowders is handled under the OSH&WC Code, 2020 (in force 21 November 2025, which replaced the Factories Act, 1948) with engineering controls and respiratory protection; occupational exposure limits specific to nanoforms are generally not notified, so control-banding is used.

Electronics: scaling, memory, displays and sensors

• Why nano is unavoidable: a transistor gate length of a few tens of nanometres and a gate dielectric a few atoms thick are nanotechnology whether or not anyone calls it that. Moore's law (transistor count doubling roughly every two years) has been sustained by device architecture, not by simple shrinking.
• Device evolution:
  1. Planar bulk MOSFET → short-channel effects (threshold roll-off, drain-induced barrier lowering, leakage) below ~100 nm.
  2. High-k/metal gate — SiO₂ replaced by HfO₂ (k ≈ 20–25) so the *equivalent oxide thickness* stays ~1 nm while the physical film is thick enough to stop tunnelling leakage.
  3. Strained silicon — tensile/compressive strain raises carrier mobility.
  4. FinFET (tri-gate) — gate wraps three sides of a thin fin; introduced in volume at the 22 nm node and standard from 16/14 nm.
  5. GAA nanosheet / nanowire — gate fully surrounds stacked channels; used at the 3 nm/2 nm generation. Node names are now marketing labels, not physical gate lengths.
• Lithography: 193 nm immersion ArF with multi-patterning down to ~10 nm features; EUV at 13.5 nm wavelength for the leading nodes. Resolution follows the Rayleigh criterion.
• Interconnects and packaging: copper damascene with ultra-thin barrier layers, low-k dielectrics; 3D stacking, through-silicon vias, chiplets and 2.5D interposers (ATMP/OSAT work).
• Memory:
  • Flash — charge stored on a floating gate/charge-trap layer; 3D NAND stacks hundreds of layers instead of shrinking laterally.
  • MRAM (STT-MRAM) — magnetic tunnel junction with an MgO barrier ~1 nm thick; non-volatile, fast, endurance far above flash.
  • RRAM/memristor — conductive filament a few nanometres wide forms and ruptures in an oxide; candidate for in-memory and neuromorphic computing.
  • PCM — amorphous/crystalline switching of a chalcogenide nanovolume.
• Magnetic recording: GMR and then TMR read heads (multilayers a few nanometres thick) raised hard-disk areal density by orders of magnitude — the classic commercial nanotechnology (Nobel Prize in Physics, 2007).
• Displays and light: quantum-dot films (CdSe, cadmium-free InP) for wide-gamut QD-LCD backlights and QD-OLED; organic LEDs with nanometre-thick organic stacks; micro-LED.
• Emerging channel materials: carbon nanotube FETs, graphene (no band gap, so poor for digital logic but excellent for RF and sensors), 2D semiconductors (MoS₂, WS₂) for ultra-thin channels.
• MEMS/NEMS sensors: accelerometers, gyroscopes, pressure and microphone dies in every smartphone; nanowire and graphene gas sensors; SAW and resonant mass sensors.
• India-specific: the India Semiconductor Mission (2021, ₹76,000 crore outlay) funds fabs and ATMP/OSAT units — Micron's assembly-and-test plant at Sanand, the Tata–PSMC fab at Dholera (mature nodes), Tata's Assam OSAT, CG Power–Renesas at Sanand, Kaynes Semicon at Sanand. Research and student fabrication access run through the Nano Mission (DST) and nanoelectronics user programmes at IISc Bengaluru and IIT Bombay; SCL Mohali operates a legacy line. India's strength today is design (a very large share of global chip-design engineering) plus new packaging, not leading-edge logic.

Energy: storage, conversion and saving

• Lithium-ion batteries: nanostructuring shortens solid-state diffusion length (t ≈ L²/D, so halving particle size cuts diffusion time four-fold) and raises rate capability.
  • Cathodes — LFP (LiFePO₄) needs carbon coating and nanosizing because of poor intrinsic conductivity; NMC/NCA for high energy; single-crystal particles for longer life.
  • Anodes — graphite 372 mAh/g; silicon ~3,579 mAh/g (Li₁₅Si₄) but ~300% volume expansion, handled with nano-Si, Si–C composites and void-engineered particles; Li₄Ti₅O₁₂ for safety and fast charge.
  • Separators and electrolytes — ceramic-coated separators, solid-state and composite electrolytes with nanofillers.
  • Smaller particles also mean more surface, so more SEI formation, more first-cycle irreversible loss and worse packing density (lower volumetric energy) — the standard trade-off question.
• Supercapacitors: charge stored electrostatically in the double layer on high-SSA carbon (activated carbon 1,000–2,000 m²/g, graphene, CNT) or pseudocapacitively (MnO₂, RuO₂, MXenes). High power density and ~10⁵–10⁶ cycles, but energy density an order of magnitude below Li-ion.
• Solar photovoltaics:
  • Crystalline silicon (PERC, TOPCon, HJT) dominates manufacturing; nanotechnology appears as nanoscale passivation layers (ALD Al₂O₃, a few nanometres), SiNₓ anti-reflection coatings and textured surfaces.
  • Dye-sensitised (Grätzel) cells — dye monolayer on a mesoporous TiO₂ nanoparticle film; the nanoporous film provides ~1,000× the projected area for dye adsorption; lab efficiencies ~11–13%.
  • Perovskite cells — solution-processed, lab efficiencies around 26–27% for single junctions and above 33% in perovskite–silicon tandems; stability and lead content are the barriers. Records move, so quote them as "about".
  • Quantum-dot and organic cells — tunable absorption, lower efficiency; useful in niche/flexible applications.
  • Indian policy context: ALMM-listed domestic modules, PLI for high-efficiency modules, PM Surya Ghar rooftop scheme; module testing to BIS standards harmonised with the IEC design-qualification and safety series.
• Fuel cells and hydrogen: platinum nanoparticles (2–5 nm) on carbon maximise active surface per gram, cutting loading to roughly 0.1–0.4 mg/cm²; nanostructured and Pt-alloy/core–shell catalysts and non-PGM alternatives reduce cost. Nanocatalysts for water electrolysis (IrO₂, NiFe-LDH) and metal-hydride/MOF hydrogen storage support the National Green Hydrogen Mission (₹19,744 crore).
• Catalysis and fuels: zeolites with nanoporous channels in refinery FCC and hydrocracking; three-way catalytic converters with nano-Pt/Pd/Rh on washcoats (BS-VI); photocatalytic TiO₂ for water and air treatment.
• Thermal and efficiency applications: silica aerogels (conductivity ~0.013–0.020 W/m·K) for pipe and building insulation; nanofluids for heat transfer; phase-change composites; nano-coatings cutting friction and wear; low-emissivity glazing under ECSBC 2024 (which succeeds ECBC 2017).

Risks, limits and the gap between lab and product

• Toxicity drivers: size (<100 nm uptake), high reactive surface, dissolution to toxic ions (Ag⁺, Cd²⁺), high aspect ratio (long rigid fibres behave fibre-like in the lung), and surface charge.
• Reproducibility: many publications report performance on milligram electrodes or single devices; scale-up changes everything — loading, packing density, calendaring, yield.
• Cost: graphene, CNT and quantum-dot inputs are expensive; an application survives only where the nanomaterial is a few percent of cost or replaces something costlier (e.g. Pt reduction).
• Life cycle and disposal: nano-enabled waste streams (batteries, e-waste) fall under the Battery Waste Management Rules, 2022 and E-Waste (Management) Rules, 2022; municipal fractions under the Solid Waste Management Rules, 2026 (which replaced the 2016 Rules from 1 April 2026).
• Characterisation obligation: no application claim is accepted without size, size distribution, surface area, surface chemistry and purity data — which is why the measurement techniques are a separate, compulsory part of the subject.

Key points

• Specific surface area - A/V = 6/d for a sphere; shrinking size 100× raises area per gram 100×, the basis of nanocatalysis and nanoelectrodes.
• Noyes–Whitney effect - dissolution rate ∝ surface area, so nanosizing raises the bioavailability of poorly soluble drugs.
• Therapeutic index - nano delivery's real gain is lower toxicity at equal efficacy (liposomal doxorubicin, liposomal amphotericin B), not higher potency.
• EPR effect - passive tumour accumulation of 10–200 nm carriers; real but variable in humans, so active targeting is added.
• PEGylation - polymer coating that reduces opsonisation and extends circulation half-life.
• LNP - ionisable-lipid nanoparticle; the enabling delivery system for mRNA vaccines.
• Superparamagnetic iron oxide - single-domain below ~20 nm, no remanence; MRI T2 contrast, separation, hyperthermia.
• High-k/metal gate - HfO₂ keeps EOT near 1 nm while stopping gate tunnelling leakage.
• FinFET → GAA - electrostatic control restored by wrapping the gate around a thin fin, then fully around stacked nanosheets.
• EUV lithography - 13.5 nm wavelength source; replaces costly multi-patterning at leading nodes.
• GMR/TMR read head - nanometre multilayers; the first mass-market nanotechnology product.
• RRAM/MRAM/PCM - non-volatile memories switching a nanoscale filament, magnetic layer or phase volume.
• Quantum-dot display - emission colour set by dot size through quantum confinement; InP for cadmium-free products.
• Diffusion length rule - t ≈ L²/D: halving electrode particle size cuts intercalation time by four, raising C-rate.
• Silicon anode - 3,579 mAh/g against graphite's 372 mAh/g, offset by ~300% volume change.
• Supercapacitor trade-off - very high power and cycle life, roughly one-tenth of Li-ion energy density.
• Pt nanocatalyst - 2–5 nm particles on carbon raise mass activity and cut PEM fuel-cell Pt loading.
• Indian regulatory anchors - CDSCO nanopharmaceutical guidelines (2019) with the New Drugs and Clinical Trials Rules, 2019; IP 2026; India Semiconductor Mission; ACC-battery PLI; National Green Hydrogen Mission.

Formulas and examples

Example 1 — surface area gained by nanosizing. A gold nanoparticle catalyst, d = 10 nm, ρ = 19,300 kg/m³.

• SSA = 6/(19,300 × 10×10⁻⁹) = 6/(1.93×10⁻⁴) = 31,088 m²/kg ≈ 31 m²/g.
• The same gold as 1 µm particles: SSA = 6/(19,300 × 1×10⁻⁶) = 311 m²/kg ≈ 0.31 m²/g — a 100× loss of active area.
• For 20 nm TiO₂ (ρ = 3,900 kg/m³) in a dye-sensitised cell: SSA = 6/(3,900 × 2×10⁻⁸) = 76,923 m²/kg ≈ 77 m²/g, which is why a 10 µm mesoporous film adsorbs enough dye to absorb sunlight in a monolayer-thick sensitiser.

Example 2 — nanoparticle dose arithmetic. A PLGA formulation: 100 mg drug added, 85 mg entrapped, polymer and excipient mass 400 mg, particle diameter 100 nm, ρ = 1,300 kg/m³ (1.3 g/cm³).

• EE = 85/100 × 100 = 85%; DL = 85/(85 + 400) × 100 = 85/485 = 17.5%.
• Volume per particle = (π/6)d³ = 0.5236 × (1×10⁻⁵ cm)³ = 5.24×10⁻¹⁶ cm³ → mass = 6.81×10⁻¹⁶ g.
• Particles in 1 mg of formulation = 1×10⁻³/6.81×10⁻¹⁶ ≈ 1.5×10¹² particles — the reason sterility, endotoxin and aggregation control dominate manufacture.

Example 3 — anode capacity, graphite versus silicon.

• Graphite, LiC₆: n = 1, M = 6 × 12.011 = 72.07 g/mol → Q = 96,485/(3.6 × 72.07) = 96,485/259.4 = 372 mAh/g.
• Silicon, Li₁₅Si₄ (3.75 Li per Si): M = 28.09 g/mol → Q = (3.75 × 96,485)/(3.6 × 28.09) = 361,819/101.1 = 3,578 mAh/g — about 9.6× graphite.
• Volume expansion ~300% means practical cells use only a few percent to ~20% silicon blended with graphite.

Example 4 — solar cell and electrode trade-off. A TOPCon cell measures Voc = 0.715 V, Jsc = 41 mA/cm², FF = 0.82.

• η = (0.715 × 41 × 0.82)/100 = 24.04/100 = 24.0%.
• A DSSC with Voc = 0.75 V, Jsc = 18 mA/cm², FF = 0.70: η = (0.75 × 18 × 0.70)/100 = 9.45/100 = 9.5% — illustrating why nanostructured third-generation cells compete on cost, flexibility or indoor light, not on efficiency.

Example 5 — supercapacitor energy and a nanofluid gain.

• A 100 F, 2.7 V carbon supercapacitor cell of mass 10 g: E = ½ × 100 × 2.7² = 364.5 J = 364.5/3,600 = 0.101 Wh → 10.1 Wh/kg, against 150–250 Wh/kg for a Li-ion cell; but it delivers that charge in seconds and survives ~10⁶ cycles.
• Al₂O₃–water nanofluid, φ = 0.02, k_p = 40, k_f = 0.60 W/m·K: numerator = 40 + 1.2 + 2(0.02)(39.4) = 42.776; denominator = 41.2 − 0.02(39.4) = 40.412; ratio = 1.059 → k_eff ≈ 0.635 W/m·K, a 5.9% rise — modest, and partly offset by higher viscosity and pumping power.

Where it is used

• Pharma and formulation R&D: Sun Pharma, Cipla, Dr Reddy's, Zydus, Intas, Bharat Serums, Serum Institute, Gennova — liposomal injectables, nanosuspensions, depot formulations, vaccine adjuvants; roles in formulation development, analytical development and regulatory affairs (CDSCO submissions).
• Diagnostics and devices: rapid test-strip manufacturers, Mylab, Trivitron, SIIC-type startups; nanoparticle conjugation, assay development, quality control.
• Semiconductors: design houses and new fabs/ATMP units — Micron Sanand, Tata–PSMC Dholera, Tata Assam, CG Power–Renesas, Kaynes, SCL Mohali; process-integration, metrology, yield, packaging and failure-analysis engineers; cleanroom work at IISc/IIT Bombay nanofabrication facilities.
• Batteries and EVs: Exide, Amara Raja, Tata Chemicals, Ola, Reliance–Faradion, Log9, Epsilon Carbon — electrode material synthesis, coating and calendaring, cell testing against AIS-156/AIS-038(Rev 2) battery-safety requirements.
• Solar and hydrogen: Adani Solar, Waaree, Tata Power Solar, Vikram Solar, Premier Energies — passivation and coating processes, cell efficiency engineering, module reliability testing; electrolyser and catalyst work under the National Green Hydrogen Mission.
• Coatings, catalysis and consumer products: Asian Paints and Pidilite nano-additive coatings, refinery and emission catalysts (BPCL, IOCL, Reliance, Hindustan Platinum), textile and water-filtration nanomaterials (Tata Swach-type silver/nano media), nano-hydroxyapatite oral care.

Interview questions

• Q: What does a nanocarrier actually improve about a drug? A: Not its potency — it changes biodistribution, solubility and release kinetics, so more drug reaches the target and less reaches healthy tissue, widening the therapeutic index.
• Q: What is the EPR effect and why is it criticised? A: Leaky tumour vasculature plus poor lymphatic drainage traps 10–200 nm particles; it is criticised because the magnitude varies enormously between tumours and species, so human benefit is far smaller than mouse data suggests.
• Q: Why PEGylate a liposome? A: The hydrophilic PEG layer resists opsonin adsorption, slowing uptake by the mononuclear phagocyte system and extending circulation half-life.
• Q: Is a nano version of an approved drug automatically bioequivalent? A: No. CDSCO treats a nanopharmaceutical as a new drug; different particle size, surface or release profile changes pharmacokinetics, so fresh characterisation and clinical data are required.
• Q: Why was HfO₂ introduced in transistors? A: Its high dielectric constant gives a thick physical film with a ~1 nm equivalent oxide thickness, keeping gate capacitance while cutting direct tunnelling leakage through the dielectric.
• Q: Why FinFET and then gate-all-around? A: Wrapping the gate around a thin body restores electrostatic control over a short channel, suppressing DIBL and sub-threshold leakage; GAA nanosheets wrap all four sides and allow channel width tuning.
• Q: Does a "3 nm node" mean a 3 nm gate length? A: No — node names are commercial labels; physical gate lengths are several times larger, and the gain comes from architecture, pitch scaling and design co-optimisation.
• Q: Why is graphene not used for digital logic transistors? A: It has zero band gap, so the device cannot be switched off properly; its poor on/off ratio suits RF, interconnect and sensing instead.
• Q: Why does nanosizing a battery electrode help, and what does it cost? A: Diffusion time scales as L²/D, so small particles charge faster; the cost is more surface for SEI formation, higher first-cycle loss, lower tap density and hence lower volumetric energy.
• Q: Why is platinum used as 2–5 nm particles in a fuel cell? A: Mass activity depends on electrochemically active surface area per gram; nanodispersion on carbon gives high surface area at low loading, cutting the cost of the most expensive component.
• Q: Quantum dots give a wider colour gamut than phosphors — why? A: Their emission wavelength is set by dot size through quantum confinement and the emission peak is narrow, giving saturated primaries instead of broad phosphor emission.
• Q: What makes a nanomaterial toxic? A: Small size enabling cellular uptake, high reactive surface generating oxidative stress, dissolution into toxic ions, high aspect ratio with fibre-like lung behaviour, and surface charge — not the bulk chemistry alone.

Common mistakes

• Claiming nanomedicine "cures" or strengthens a drug, instead of explaining altered biodistribution and toxicity.
• Treating EPR as a reliable, large effect in patients, or assuming a surface ligand guarantees targeting when circulation and the protein corona dominate.
• Quoting lab-record solar or battery numbers as commercial performance; always separate certified cell records, module efficiency and pack-level energy.
• Mixing units in surface-area and capacity work — m²/kg with m²/g, nm with µm, mAh/g with Ah/kg (they are numerically equal, but students often convert twice).
• Saying node names equal physical dimensions, or claiming Moore's law was sustained by shrinking alone.
• Writing silicon's 3,579 mAh/g as if it were achievable in a commercial cell, and ignoring the ~300% volume expansion and SEI instability.
• Omitting the regulatory and safety side — in Indian exams and interviews, CDSCO's 2019 nanopharmaceutical guidelines, the New Drugs and Clinical Trials Rules, 2019, and nano-dust control under the OSH&WC Code, 2020 are marks you simply lose.

Related topics

Nanoscience fundamentals: size effects and quantum confinement · Nanomaterials · Synthesis of nanomaterials: top-down and bottom-up · Nanocharacterisation: AFM, DLS and BET surface area · Materials characterisation: XRD, SEM and TEM · Semiconductor devices and VLSI fabrication