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Nanometre
Nanometre
Nanometre
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nanometre
One nanometric carbon nanotube, photographed with scanning tunneling microscope
General information
Unit systemSI
Unit oflength
Symbolnm
Conversions
1 nm in ...... is equal to ...
   SI units   1×10−9 m
   1×103 pm
   Natural units   6.1877×1025 ℓP
 18.897 a0
   imperial/US units   3.9370×10−8 in
Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The nanometre is often used to express dimensions on an atomic scale and mostly in the molecular scale.

The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling), is a unit of length in the International System of Units (SI), equal to one billionth (short scale) or one thousand million (long scale) of a metre (0.000000001 m) and to 1000 picometres. One nanometre can be expressed in scientific notation as 1 × 10−9 m and as ⁠1/1000000000⁠ m.

History

[edit]

The nanometre was formerly known as the "millimicrometre" – or, more commonly, the "millimicron" for short – since it is ⁠1/1000⁠ of a micrometre. It was often denoted by the symbol mμ or, more rarely, as μμ (however, μμ should refer to a millionth of a micron).[1][2][3]

Etymology

[edit]

The name combines the SI prefix nano- (from the Ancient Greek νάνος, nanos, "dwarf") with the parent unit name metre (from Greek μέτρον, metron, "unit of measurement").

Usage

[edit]

Nanotechnologies are based on physical processes which occur on a scale of nanometres (see nanoscopic scale).[1]

The nanometre is often used to express dimensions on an atomic scale: the diameter of a helium atom, for example, is about 0.06 nm, and that of a ribosome is about 20 nm. The nanometre is also commonly used to specify the wavelength of electromagnetic radiation near the visible part of the spectrum: visible light ranges from around 400 to 700 nm.[4] The ångström, which is equal to 0.1 nm, was formerly used for these purposes.

Since the late 1980s, in usages such as the 32 nm and the 22 nm semiconductor node, it has also been used to describe typical feature sizes in successive generations of the ITRS Roadmap for miniaturized semiconductor device fabrication in the semiconductor industry.

Unicode

[edit]

The CJK Compatibility block in Unicode has the symbol U+339A ㎚ SQUARE NM.

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Nanometre

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from Grokipedia
The nanometre (symbol: nm), also known as the nanometer in , is a in the (SI), equal to one billionth of a , or exactly 10-9 m. This unit is essential for quantifying extremely small distances, such as those encountered in atomic structures, molecular interactions, and the wavelengths of and visible light. In practical terms, a nanometre is roughly 100,000 times smaller than the average diameter of a hair, which measures about 60,000–100,000 nm across. For comparison, everyday objects like a sheet of are approximately 100,000 nm thick, while biological entities such as the width of double helix span about 2 nm and viruses range from 20–400 nm in size. The nanoscale—generally defined as the range from 1 to 100 nm—represents a critical domain in science and , where materials and structures often display unique physical, chemical, and biological properties arising from quantum mechanical effects and high surface-area-to-volume ratios. These properties enable applications in , including advanced , , and energy-efficient materials, driving innovations across disciplines like , , and .

Definition and Scale

Precise Definition

The nanometre (symbol: nm) is a in the (SI), defined as one billionth of a , or exactly 10−910^{-9} m. The prefix "nano-", with symbol n, represents a factor of 10−910^{-9} and is one of the twenty-four standard SI prefixes used to denote decimal submultiples of SI units, including the base , the . The itself is the of , defined by fixing the numerical value of the in cc to exactly 299 792 458 m/s, where the second is the of time defined by caesium hyperfine . As such, the nanometre is a coherent derived SI unit, directly scaled from the to express very small lengths. In terms of other units, 1 nm equals exactly 10 ångströms (Å), a non-SI unit historically used in and and defined as exactly 10−1010^{-10} m. The nanometre plays a crucial role in measuring dimensions at the atomic and molecular scales, where typical atomic diameters range from about 0.1 nm to 0.5 nm and molecular structures often span a few nanometres.

Comparisons to Other Units

The nanometre (nm) is defined as one billionth of a , or 1 nm=10−9 m1 \, \mathrm{nm} = 10^{-9} \, \mathrm{m}. It relates to other units as follows: 1 nm=10 A˚1 \, \mathrm{nm} = 10 \, \AA (ångströms), where the ångström is a non-SI unit equal to 0.1 nm0.1 \, \mathrm{nm}; 1 nm=0.001 μm1 \, \mathrm{nm} = 0.001 \, \mu\mathrm{m} (micrometres); and 1 nm=10−6 mm1 \, \mathrm{nm} = 10^{-6} \, \mathrm{mm} (millimetres). These conversions highlight the nanometre's position in the , bridging atomic and macroscopic scales. To grasp its minuteness, consider everyday analogies: the wavelengths of visible light range from approximately 400 nm (violet) to 700 nm (red), meaning a single nanometre is a fraction of the light we perceive. The diameter of a is about 0.1 nm, so ten such atoms aligned would span one nanometre. In contrast, the average width of a hair is around 80,000 nm (or 80 μm), equivalent to 800,000 hydrogen atoms side by side. On the broader length scale spectrum, the nanometre occupies a transitional realm: far larger than the Planck length (1.616×10−35 m1.616 \times 10^{-35} \, \mathrm{m}), the smallest scale in theories, yet vastly smaller than human-scale distances like a . For astronomical context, one —the distance light travels in a year—is about 9.46×1015 m9.46 \times 10^{15} \, \mathrm{m}, underscoring the nanometre's proximity to atomic dimensions amid cosmic vastness. A relatable proportion illustrates this: one nanometre is to one metre as a marble (about 1 cm in diameter) is to Earth (about 12,742 km in diameter), emphasizing the extreme smallness of nanoscale features relative to everyday objects.

Historical Development

Origin of the Prefix

The prefix "nano-" originates from the Greek word nanos (νᾶνος), meaning "dwarf" or "very small," a term historically associated with diminutive figures in mythology and language. This etymological root reflects the prefix's purpose in denoting scales of extreme minuteness, drawing from ancient linguistic traditions to describe something exceedingly tiny. In scientific , the "nano-" prefix was formally proposed in 1947 during the 14th Conference of the International Union of Pure and Applied Chemistry (IUPAC) in , where it was designated to represent a factor of 10^{-9}, or one billionth. This introduction addressed the need for a standardized term to quantify submicroscopic lengths, building on earlier informal usages. Prior to this, smaller scales relied on units like the micron (μ, equivalent to 10^{-6} m), introduced in the late for microscopic measurements, and the millimicron (mμ, or 10^{-3} μ = 10^{-9} m), which had gained traction in colloid chemistry and during the and . The millimicron, while practical, was cumbersome as a double prefix, prompting the search for a simpler alternative. Notably, German Richard Adolf had already employed the term "nanometer" in his research on gold colloids, using it to specify particle diameters around 1/1,000,000 of a millimeter, though without formal metric status at the time. By the early 1950s, the "nano-" prefix began appearing in physics and chemistry , particularly in fields like and , where precise of atomic and molecular dimensions was essential. For instance, it facilitated descriptions of wavelengths in and particle sizes in experiments, gradually supplanting the millimicron notation for clarity and consistency. This early adoption in scientific publications laid the groundwork for its broader integration into the by 1960, though details of that standardization belong to later developments.

Standardization and Adoption

The nanometre (nm), defined as one billionth of a (10^{-9} m), was formally incorporated into the (SI) through Resolution 12 of the 11th General Conference on Weights and Measures (CGPM) in 1960, which established the SI framework and included the "nano-" prefix among the standard decimal multipliers for all base units, including the . This adoption built on earlier conventions but integrated them into the newly named Système International d'Unités, ensuring consistency in scientific measurement across disciplines. Usage of the nanometre expanded significantly in the post-1980s era, driven by breakthroughs in (SPM), such as the invention of the (STM) in 1981, which enabled atomic-scale imaging and routinely employed nanometre units for resolution and feature sizing. By the 1990s, the nanotechnology boom—marked by discoveries like carbon nanotubes in 1991—propelled the nanometre from niche applications in to a universal standard for describing structures and phenomena at the 1–100 nm scale, reflecting its growing indispensability in interdisciplinary research. International standards bodies have played a pivotal role in standardizing the nanometre's symbol and conventions. The (ISO), through ISO 80000-1:2022, defines the nanometre as 10^{-9} m and endorses "nm" as its symbol for use in quantities and units. Similarly, the National Institute of Standards and Technology (NIST) affirms "nm" in its SI guidelines, promoting uniform application in and . The International Union of Pure and Applied Chemistry (IUPAC), in its Quantities, Units and Symbols in Physical Chemistry (Green Book, 2007), reinforces "nm" for and measurements, ensuring alignment with SI practices.

Applications

In Nanotechnology and Materials Science

Nanotechnology is defined as the understanding and control of matter at the nanoscale, typically involving dimensions between 1 and 100 nanometres, to create materials, devices, and systems with novel properties and functions. This scale enables engineers to manipulate atoms and molecules to design structures that exhibit behaviors distinct from their bulk counterparts. At the nanometre scale, quantum effects become prominent, altering the electrical, optical, and mechanical properties of materials due to quantum confinement, where electrons are restricted in space, leading to discrete energy levels rather than continuous bands. Additionally, the high surface-to-volume ratio of dramatically increases reactivity, as a greater proportion of atoms reside on the surface, enhancing interactions with surrounding environments. For instance, carbon nanotubes, which have diameters typically ranging from 1 to 10 nanometres, demonstrate exceptional tensile strength and electrical conductivity owing to these nanoscale phenomena. In , nanoparticles serve as highly efficient catalysts because their small size maximizes active surface sites for chemical reactions, such as in processes where nanoparticles accelerate reaction rates under mild conditions. Nanocomposites, incorporating nanofillers like carbon nanotubes into matrices, significantly enhance mechanical strength and toughness. Key tools for probing and fabricating at this scale include (AFM), which achieves lateral resolutions down to approximately 1 nanometre, allowing visualization and manipulation of surface features at the atomic level. The conceptual foundations of trace back to Richard Feynman's 1959 lecture "There's Plenty of Room at the Bottom," which envisioned manipulating matter atom by atom, inspiring subsequent developments in nanometre-scale engineering.

In Biology and Medicine

In , the nanometre scale is essential for understanding the dimensions of key biomolecular structures. The DNA double , for instance, has a diameter of approximately 2 nm, allowing it to fit within the confines of cellular nuclei while enabling intricate packaging mechanisms. Proteins, the building blocks of cellular function, typically range in size from 1 to 10 nm, influencing their folding, interactions, and roles in enzymatic processes. Cell membranes, composed of bilayers, are about 5 nm thick, providing a selective barrier that regulates molecular transport and signaling. Viruses and antibodies further exemplify the relevance of nanometre-scale measurements in immunology and virology. Most viruses measure between 20 and 300 nm in diameter, with their size directly affecting infectivity, immune evasion, and vaccine design strategies. Antibodies, such as immunoglobulin G (IgG), have dimensions on the order of 10 nm, enabling precise binding to antigens on pathogen surfaces for neutralization. Advanced imaging techniques leverage the nanometre to visualize these structures at unprecedented detail. Cryo-electron microscopy (cryo-EM) preserves biological samples in vitreous ice and achieves resolutions down to the nanometre scale, revealing conformational changes in proteins and macromolecular complexes. Super-resolution techniques, including stochastic optical reconstruction (STORM) and stimulated emission depletion (STED), surpass the diffraction limit of conventional light —approximately 200 nm—allowing localization of fluorescently labeled biomolecules with 20-50 nm precision. In , nanometre-scale enhances therapeutic interventions, particularly through targeted delivery systems. Liposomes, spherical vesicles with diameters around 100 nm, encapsulate drugs for site-specific release, improving and reducing systemic in treatments for cancer and infections. Conceptual frameworks for nanobots—hypothetical devices operating at 10-100 nm—envision autonomous navigation through bloodstreams to perform tasks like precise or real-time diagnostics, though current prototypes focus on passive targeting rather than full mobility.

In Physics and Electronics

In fundamental physics, the nanometre scale is crucial for describing phenomena involving light and atomic structures. (UV) light, which spans wavelengths from approximately 100 nm to 400 nm, plays a key role in and , where precise measurements at this scale enable the study of molecular interactions and material properties. Similarly, atomic orbitals, which define the spatial distribution of electrons around nuclei, have characteristic sizes on the order of 0.1 nm; for instance, the for the atom's 1s orbital is 0.0529 nm, setting the fundamental length scale for quantum mechanical descriptions of atoms. In electronics, the nanometre unit underpins the scaling described by , which has driven exponential increases in transistor density by reducing feature sizes, enabling the integration of billions of s on chips. As of 2025, advanced semiconductor process nodes, such as TSMC's 2 nm technology entering , feature gate lengths around 12 nm, allowing for enhanced performance and power efficiency in devices like microprocessors and GPUs while approaching physical limits imposed by quantum effects. At these scales, quantum phenomena become prominent; for example, quantum tunneling in nanometre-scale junctions permits electrons to pass through insulating barriers as thin as 1-3 nm, which is essential for operations in but poses challenges like leakage currents in ultra-scaled s. Ballistic transport, where electrons travel through nanowires without scattering over lengths up to several hundred nanometres, further exemplifies how nm-scale engineering minimizes resistance and enables high-speed signal propagation in nanoscale interconnects. Nanometre precision is integral to fabricating key electronic devices. Quantum dots, semiconductor nanocrystals typically 2-10 nm in diameter, exhibit size-dependent optical and electrical properties due to quantum confinement, making them ideal for applications in photodetectors and single-photon sources. In light-emitting diodes (LEDs), active layers and quantum wells are engineered with thicknesses on the order of 1-100 nm to optimize carrier recombination and emission efficiency, as seen in high-brightness GaN-based LEDs where precise nm-scale layering enhances output power and color purity.

Notation and Representation

Symbols and Usage Conventions

The standard symbol for the nanometre in the (SI) is "nm", consisting of the prefix symbol "n" for nano (10^{-9}) combined with the symbol "m" for , with no space between the prefix and the base unit symbol. Unit symbols like "nm" are always written in roman (upright) typeface, regardless of the surrounding text style, and are not italicized. According to SI conventions established by the International Bureau of Weights and Measures (BIPM), the numerical value precedes the unit with a single space separating them, as in "5 nm" for five nanometres; no space is used before the in the compound form. Unit s do not change form for plural quantities, so "nm" is used whether singular or plural, while the spelled-out name follows standard English pluralization as "nanometre" or "nanometres" in international contexts, preferring the British "" to align with the original French "mètre". In textual writing, "nm" is preferred for brevity, whereas in mathematical equations, the explicit form 10−910^{-9} m is recommended to denote the nanometre precisely. A common error in scientific notation arises from potential ambiguity with the millinewton-metre (a unit of torque, symbol mN·m), which may be ambiguously written as "mNm" without separators; to distinguish it clearly from "nm", the SI recommends inserting a raised dot (·) or a space in compound units, such as "m N·m" or "m N m". This practice ensures unambiguous communication in technical documents, as outlined in the BIPM SI Brochure.

Digital and Typographic Representation

In digital systems, the nanometre symbol "nm" is encoded using the standard Latin lowercase letters "n" ( U+006E LATIN SMALL LETTER N) and "m" ( U+006D LATIN SMALL LETTER M), as there is no dedicated Unicode character for the unit in the primary ranges. A compatibility character, U+339A ㎚ SQUARE NM, exists in the CJK Compatibility block for legacy East Asian approximating "nm", but it is not recommended for general use in SI-compliant documents. Typographically, "nm" is rendered in upright (roman) font to distinguish it from variables, per SI conventions, with a or separating the preceding numeral to prevent line breaks, as in "5 nm". In some typefaces, the adjacent rounded forms of "n" and "m" can lead to suboptimal default , requiring manual adjustment in design software for balanced spacing in technical contexts. For digital typesetting tools, supports "nm" via the siunitx package, using commands like \si{\nano\metre} to produce properly formatted output with correct spacing and font. In and CSS, the unit is simply written as text, with non-breaking spaces (&nbsp;) or CSS properties like white-space: nowrap applied to the number-unit pair for layout control, and superscript notation (e.g., via <sup>2</sup>) for powers like nm². Historically, before widespread adoption in the , the nanometre was represented in ASCII-based systems simply as the sequence "nm", leveraging the basic Latin alphabet available since ASCII standardization in , without special encoding.

References

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