Ozizi Isi nke Fizik Plasmonic
Plasmonic physics bụ ngalaba sayensị nke na-amụ mmekọrịta dị n'etiti ebili mmiri electromagnetic (ìhè) na elektrọn efu n'elu ma ọ bụ ihe dị n'ime, ọkachasị ọla. Ubi a na-etolite ngwa ngwa n'ihi na ọ nwere ike "ịpịachi" ìhè ruo n'ogo dị obere karịa ogologo ebili ya, si otú a na-emepe nnukwu ohere maka teknụzụ sensọ ultrasensitive, photonics agbakwunyere, na mgbanwe ike na nanoscale. Iji ghọta plasmonics nke ọma, anyị kwesịrị inyocha ntọala ozizi ya: ọdịdị nke elektrọn efu na ọla, nzaghachi dielectric nke ihe, ọnọdụ resonance, na ụdị mkpali plasmon kachasị mkpa.
1. Elektrọn efu na ụdị Drude
Enwere ike ịkọwa ọtụtụ ihe dị na plasmonic site na iji ụdị Drude, ihe nlereanya dị mfe nke na-ewere elektrọn conduction dị na metal dị ka "gas" nke elektrọn efu nke nwere ike ịkwaga n'okpuru mmetụta nke ubi eletrik. Mgbe ìhè kụrụ ígwè ahụ, ubi eletrik na-amanye elektrọn conduction ka ha na-agbagharị. Oscillation a na-eme ka polarization na currents pụta, nke na-agbanwe otu ebili mmiri electromagnetic si agbasa ma ọ bụ na-egosipụta.
N'ihe nlereanya Drude, a na-ede mmeghachi omume nke ígwè na ugboro angular nke ìhè, \( \omega \), site na ikike mgbagwoju anya:
\[
\varepsilon(\omega)=\varepsilon_\infty-\frac{\omega_p^2}{\omega^2+i\gamma\omega}
\]
Ebe:
– \( \varepsilon_\infty \) na-anọchite anya onyinye dị na ugboro dị elu (dịka ọmụmaatụ site na elektrọn ejikọtara),
– \( \omega_p \) bụ ugboro ole plasma dị,
– \( \gamma \) bụ ọsọ mmiri (nsogbu nke elektrọn na lattice, ntụpọ, ma ọ bụ phonon).
Ugboro plasma \( \omega_p \) metụtara njupụta elektrọn efu \(n \), chajị elektrọn \(e \), oke dị irè \( m^ \ \), na ikike ikuku vacuum \( \varepsilon_0 \):
\[
\omega_p=\sqrt{\frac{ne^2}{\varepsilon_0 m^\}}
\]
N'ụzọ anụ ahụ, n'okpuru ugboro plasma, ọla na-egosipụtakarị ìhè n'ihi na elektrọn nwere ike "ịcha" mpaghara eletriki. Karịa ugboro plasma, nzaghachi metal ahụ nwere ike ịdị ka dielectric karịa.
2. Nkwenye dị mgbagwoju anya na ihe ọ pụtara
N'ime plasmonics, permittivity mgbagwoju anya \(\varepsilon(\omega)=\varepsilon'(\omega)+i\varepsilon"(\omega)\) dị oke mkpa. Akụkụ dị adị \(\varepsilon'\) metụtara otu ebili mmiri si "gbagọọ" ma ọ bụ gbanwee ọnọdụ, ebe akụkụ echiche \(\varepsilon"\) na-akọwa mfu (ntinye) n'ihi mwepụ ike dị ka okpomọkụ (dịka ọmụmaatụ okpomọkụ Joule).
Ihe achọrọ maka mkpali plasmon ime bụ na ikike nke ígwè ahụ ga-adị njọ n'oge ụfọdụ. Maka ọla ndị dị ebube dịka ọlaedo (Au) na ọlaọcha (Ag), \(\varepsilon'\) bụ ihe na-adịghị mma n'ebe a na-ahụ anya ruo nso na infrared, na-eme ka a na-ejikarị ha eme ihe dị ka ikpo okwu plasmonic.
3. Plasmon: njikọta nke elektrọn
Okwu ahụ bụ "plasmon" na-ezo aka na oke nke oscillation nke elektrọn efu na ihe na-eme n'ime igwe. E nwere isi ihe abụọ a na-atụlekarị:
1. Plasmon olu (nnukwu plasmon): mgbanwe na-eme n'ime olu ígwè nwere ugboro ole e ji mara ya dị nso na \(\omega_p\). Ihe mkpali ndị a anaghị ejikọ ozugbo na foton efu n'ihi oke ọkụ eletrik.
2. Plasmon elu: oscillations mkpokọta nke ejikọtara na njikọ metal-dielectric. Ndị a bụ isi nke plasmonics nke oge a, ebe ha nwere ike ijikọ nke ọma na ìhè n'okpuru ọnọdụ ụfọdụ ma mepụta mpaghara dị nso.
4. Polariton plasmon dị n'elu (SPP)
N'ebe dị larịị dị n'etiti ígwè na dielectric, ihe mkpali kachasị pụta ìhè bụ polaritons plasmon dị n'elu (SPPs), nke bụ ebili mmiri ndị a na-ejikọta ọnụ nke ụdị electromagnetic na oscillations electron.
Enwere ike ide njikọ mgbasa SPP maka njikọ metal (permittivity \(\varepsilon_m\)) na dielectric (\(\varepsilon_d\)) dịka ndị a:
\[
k_{\text{SPP}} = k_0 \sqrt{\frac{\varepsilon_m \varepsilon_d}{\varepsilon_m+\varepsilon_d}}
\]
ebe \(k_0=\omega/c\) bụ nọmba ebili mmiri dị na oghere ikuku. SPP nwere ihe ndị dị mkpa:
– A na-ahụ ebe elektrọnik dị nso n'elu ma na-ere ọkụ nke ukwuu n'ebe metal na dielectric dị.
– Uru nke \(k_{\text{SPP}}\) na-adịkarị karịa \(k_0\) (n'ime igwe dielectric), nke mere na SPP nwere ike ịbawanye ọsọ karịa photons efu n'otu ugboro.
N'ihi ya, a pụghị ịkpọlite SPP ozugbo site na ìhè sitere na ikuku na-enweghị usoro ndị ọzọ iji "tinye ọkụ ọkụ", dịka ọmụmaatụ site na prisms (nhazi Kretschmann ma ọ bụ Otto), njikọ grating, ma ọ bụ mgbasa site na adịghị mma elu.
5. Resonance plasmon dị n'elu mpaghara (LSPR)
Ọ bụrụ na ígwè ahụ abụghị ụgbọelu kama ọ bụ nanoparticle (dịka ọmụmaatụ, sphere nanometer ma ọ bụ nanostructure ndị ọzọ), plasmons elu nwere ike ịghọ ebe dị iche iche ma mepụta resonance a na-akpọ localized surface plasmon resonance (LSPR). LSPR na-eme mgbe ọkụ na-akpali electrons conduction iji mepụta dipoles (ma ọ bụ multipoles) nke na-agbanwe agbanwe na ugboro ole ìhè ahụ na-emekọrịta.
Maka obere nanoparticles (radius pere mpe karịa wavelength), a na-ejikarị usoro quasi-static eme ihe. Resonance dipole dị mfe nke ihe dị n'ime ihe dị n'ime dielectric na-eme ihe dịka mgbe:
\[
\ederede{Re}[\varepsilon_m(\omega)] \approx -2\varepsilon_d
\]
N'ebe a na-akpọ resonance, nanoparticles na-emepụta:
- nnukwu uru dị nso n'ọhịa,
- ike ịmịkọrọ na ịgbasa ìhè,
- nnukwu mmetụta uche maka mgbanwe na ntinye anya nke gburugburu ebe obibi.
Ọ bụ ya mere e ji eji LSPR eme ihe maka ihe mmetụta kemịkalụ na ihe mmetụta biosensọ, dịka ọmụmaatụ ịchọpụta njikọ molekul site na mgbanwe na oke resonance spectrum.
6. Ebe dị nso, mkpakọ ọkụ, na oke mgbasa ozi
Otu n'ime ihe ndị na-adọrọ mmasị nke plasmonics bụ ikike ya ịgafe oke mgbasa nke optics oge ochie. Na optics ọdịnala, isi ihe nke ìhè na-elekwasị anya bụ ihe dịka \(\sim \lambda/2\). Agbanyeghị, ụdị plasmon (SPP na LSPR) nwere ike "ịpịachi" ike elektrọnik n'ime obere mpaghara, ọbụlagodi ọtụtụ iri nanomita ma ọ bụ ihe na-erughị ya, n'ihi na ubi a na-ejikọta elu nwere nnukwu ihe na-akpali akpali (ugboro ole dị elu).
Plasmonic dị nso na-erekwa ngwa ngwa ka anya dị, yabụ mmekọrịta ahụ dị oke nso. Nke a dị mkpa maka:
- nyocha spectroscopy nke e mere ka ọ dịkwuo mma n'ọhịa (dịka ọmụmaatụ SERS: mgbasa Raman nke e mere ka ọ dịkwuo mma n'elu),
- mmụba nke mmepụta (mmetụta Purcell) na ndị na-ewepụta kwantum,
- ihe onyonyo na-abụghị ahịrị na nanoscale.
7. Mfu na ogologo nke ihe na-agagharị agagharị
Ọ bụ ezie na plasmonics na-enye ohere maka mmụba ubi na mkpakọ ìhè, mfu bụ nnukwu ihe ịma aka. Mfu sitere na:
- ohmic damping: a na-agbanwe ike ubi ka ọ bụrụ okpomọkụ na ígwè ahụ,
- mgbasa ozi n'ihi oke ike ma ọ bụ oke ntụpọ,
– mfu radieshon na nanoparticles (karịsịa ka nha na-abawanye nke mere na mgbasa na-abawanye).
Maka SPPs na njikọ dị larịị, mfu ndị a na-eme ka oke ya belata n'akụkụ mgbasa, na-ebute ogologo mgbasa nwere njedebe. Na LSPRs, mfu ndị ahụ na-ekpebi obosara nke oke resonance: mfu ndị ahụ na-ebu ibu, otú ahụ ka resonance (ala Q-factor) na mbelata uru ubi.
Mgbalị iji belata mfu gụnyere nhọrọ ihe (Ag na-enwekarị mfu dị ala karịa Au na ìhè a na-ahụ anya), nhazi geometric, njikọta na dielectrics dị elu, na ọbụna iji ihe ndị ọzọ dịka aluminom (UV), ọla kọpa, nitride (TiN), ma ọ bụ graphene (karịsịa maka etiti IR ruo THZ).
8. Njikọ Plasmonic na nhazi ụdị
N'ime usoro dị mgbagwoju anya—dịka nanoparticle dimers, nanoantennas, ma ọ bụ nanogaps—ụdị plasmon nwere ike ịkpakọrịta onwe ha ma mepụta ụdị ọhụrụ, nke yiri echiche nke orbital hybridization na kemistri. Mgbe ejikọtara nanoparticles abụọ nso, ubi dị n'ime oghere ahụ nwere ike ibu nnukwu (ebe na-ekpo ọkụ), nke bara uru nke ukwuu maka SERS na nchọpụta otu molekul.
Tinyere nke ahụ, plasmons nwere ike ijikọ ya na excitons na semiconductors ma ọ bụ molekul, nke na-ebute ihe njikọ siri ike na ịmepụta polaritons ngwakọ. Nke a dị mkpa maka njikwa mwepụta, fotokemistri ntụziaka, na ngwaọrụ anya quantum.
9. Ntuziaka na ngwa nyocha
Site na ntọala ozizi dị n'elu, a na-eji plasmonics eme ihe n'ọtụtụ ngwa:
- Biosensors na sensọ ntụaka refractive dabere na LSPR ma ọ bụ SPP,
- SERS maka nyocha kemịkalụ dị oke nro,
- Photonics ejikọtara ya na plasmonic waveguides maka obere mgbanwe,
- Photothermal (kpo oku mpaghara) maka ọgwụgwọ, catalysis, ma ọ bụ microprocessing,
- Mbara mmiri nke plasmonic maka imegharị usoro ìhè na polarization.
N'ọdịnihu, ihe ịma aka dị mkpa ga-abụ ịhazi nrụgide ubi na mfu ike. Nnyocha na-agakwa n'ihu na ihe ọhụrụ, nhazi plasmonic-dielectric ngwakọ, na ijikọ ya na teknụzụ semiconductor na ngwaọrụ quantum.
Penutup
Ntọala echiche nke physics plasmonic sitere na nzaghachi mkpokọta nke elektrọn efu na ọla na ubi electromagnetic, nke a kọwara nke ọma site na ikike dị mgbagwoju anya na ụdị Drude. Site na nke a pụta ìhè echiche nke plasmons elu - ma SPPs na njikọ dị larịị na LSPRs na nanoparticles - nke na-eme ka mmụba dị nso na mkpakọ ìhè na nanoscale. N'agbanyeghị oke n'ihi mfu ihe, plasmonics ka bụ ubi na-arụ ọrụ nke ukwuu, na-ejikọta optics, sayensị ihe, na nanotechnology iji mepụta ngwaọrụ na ụzọ nha nwere mmetụta na mkpebi nke optics ọdịnala na-apụghị iru.
