Khopolo-taba ea Motheo ea Fisiks ea Plasmonic
Fisiks ea plasmonic ke lekala la mahlale le ithutang likamano lipakeng tsa maqhubu a motlakase (leseli) le lielektrone tse lokolohileng holim'a metsi kapa thepa e ka hare, haholo-holo litšepe. Tšimo ena e ntse e hola ka potlako hobane e ka "hatella" leseli ho isa tekanyong e nyane haholo ho feta bolelele ba lona ba maqhubu, kahoo e bula menyetla e meholo bakeng sa theknoloji ea sensor e utloang haholo, li-photonics tse kopantsoeng, le phetoho ea matla ho nanoscale. Ho utloisisa ka botlalo li-plasmonics, re hloka ho hlahloba metheo ea eona ea khopolo-taba : mofuta oa lielektrone tse lokolohileng litšepeng, karabelo ea dielectric ea thepa, maemo a resonance, le mefuta ea bohlokoa ka ho fetisisa ea ho hlasimolla plasmon.
1. Lielektrone tse lokolohileng le mohlala oa Drude
Liketsahalo tse ngata tsa plasmonic li ka hlalosoa qalong ho sebelisoa mohlala oa Drude, mohlala o bonolo o nkang lielektrone tsa conduction ka har'a tšepe e le "khase" ea lielektrone tse lokolohileng tse ka tsamaeang tlas'a tšusumetso ea tšimo ea motlakase. Ha leseli le otla tšepe, tšimo ea motlakase e qobella lielektrone tsa conduction ho sisinyeha. Ho sisinyeha hona ho kopaneng ho baka polarization le maqhubu, a ntan'o fetola tsela eo maqhubu a motlakase a jalang kapa a bonahatsang ka eona.
Mohlaleng oa Drude, karabelo ea tšepe ho maqhubu a angular a khanya, \( \omega \), e ngotsoe ka mokhoa o rarahaneng oa permittivity:
\[
\varepsilon(\omega)=\varepsilon_\infty-\frac{\omega_p^2}{\omega^2+i\gamma\omega}
\]
Moo:
– \( \varepsilon_\infty \) e emela monehelo maqhubung a phahameng (mohlala, ho tsoa ho dielektrone tse tlamilweng),
– \( \omega_p \) ke maqhubu a plasma,
– \( \gamma \) ke sekhahla sa ho damping (ho thulana ha dielektrone le letlooeng, diphoso, kapa difonone).
Maqhubu a plasma \( \omega_p \) a amana le bongata ba dielektrone tse lokolohileng \( n \), tjhaja ya dielektrone \( e \), boima bo sebetsang \( m^\ \), le tumello ya vacuum \( \varepsilon_0 \):
\[
\omega_p=\sqrt{\frac{ne^2}{\varepsilon_0 m^\ }}
\]
Ka 'mele, ka tlase ho maqhubu a plasma, litšepe li atisa ho bonahatsa hobane lielektrone li khona ho "sefa" tšimo ea motlakase. Ka holim'a maqhubu a plasma, karabelo ea tšepe e ka tšoana le ea dielectric haholoanyane.
2. Tumello e rarahaneng le moelelo oa eona
Ho plasmonics, permittivity e rarahaneng \(\varepsilon(\omega)=\varepsilon'(\omega)+i\varepsilon”(\omega)\) e bohlokoa haholo. Karolo ea 'nete \(\varepsilon'\) e amana le kamoo leqhubu le "kobehang" kapa le fetolang mohato, ha karolo e inahaneloang \(\varepsilon”\) e hlalosa tahlehelo (ho monngoa) ka lebaka la ho qhalana ha matla e le mocheso (mohlala, ho futhumatsa ha Joule).
Tlhokahalo e akaretsang ea hore ho be le pherekano ea plasmon ke hore tumello ea 'nete ea tšepe e lokela ho ba mpe ka makhetlo a itseng. Bakeng sa litšepe tse ntle tse kang khauta (Au) le silevera (Ag), \(\varepsilon'\) ehlile e mpe sebakeng se bonahalang ho isa haufi le infrared, e leng se etsang hore li sebelisoe khafetsa e le liforomo tsa plasmonic.
3. Plasmon: ho sisinyeha ha dielektrone ka kakaretso
Lentsoe "plasmone" le bolela quanta ea ho sisinyeha ha lielektrone tse lokolohileng ka har'a seaplane. Ho na le mekhahlelo e 'meli e meholo eo hangata ho buuoang ka eona:
1. Bongata ba plasmone (plasmone e ngata): ho sisinyeha ho etsahala ka har'a bophahamo ba tšepe bo nang le maqhubu a ikhethang a haufi le \(\omega_p\). Hangata menyaka ena ha e hokahane ka kotloloho le li-photon tse lokolohileng ka lebaka la lithibelo tsa lebelo.
2. Li-plasmone tsa bokaholimo: ho sisinyeha ha 'mele ho tlamahaneng le sebopeho sa tšepe le dielectric. Tsena ke pelo ea li-plasmoni tsa sejoale-joale, kaha li ka kopana ka matla le leseli tlas'a maemo a itseng 'me tsa hlahisa sebaka se haufi le sebaka se matla.
4. Polariton ea plasmone ea bokaholimo (SPP)
Sebakeng se bataletseng sa tshepe le dielectric, ntho e hlahelletseng ka ho fetisisa ke di-polariton tsa plasmon tsa bokaholimo (SPPs), e leng maqhubu a tlamilweng hodima bokaholimo a leng motswako wa mekgwa ya electromagnetic le ho sisinyeha ha dielectric.
Kamano ea ho hasana ha SPP bakeng sa li-interface tsa tšepe (permittivity \(\varepsilon_m\)) le dielectric (\(\varepsilon_d\)) e ka ngoloa ka tsela ena:
\[
k_{\text{SPP}} = k_0 \sqrt{\frac{\varepsilon_m \varepsilon_d}{\varepsilon_m+\varepsilon_d}}
\]
moo \(k_0=\omega/c\) e leng nomoro ya maqhubu a ka hara vacuum. SPP e na le dibopeho tsa bohlokwa:
- Masimo a motlakase e fumaneha haufi le bokaholimo 'me e bola ka potlako ho ea ho tšepe le dielectric.
– Boleng ba \(k_{\text{SPP}}\) hangata bo feta \(k_0\) (ka har'a dielectric medium), e le hore SPP e be le motsamao o sebetsang hantle ho feta di-photon tse lokolohileng ka maqhubu a tšoanang.
Ka lebaka leo, li-SPP li ke ke tsa tsosoa ka kotloloho ke khanya ea tšohanyetso e tsoang moeeng ntle le mekhoa e meng ea ho "eketsa lebelo", mohlala ka li-prism (li-configurations tsa Kretschmann kapa Otto), ho kopanya grating, kapa ho hasana ho tsoa ho se tsitse ha bokaholimo.
5. Ho utloahala ha plasmone ea bokaholimo sebakeng se itseng (LSPR)
Haeba tshepe e se sefofane empa e le nanoparticle (mohlala, nanometer sphere kapa nanostructure e nngwe), di-plasmone tsa bokahodimo di ka fetoha tsa bodulo mme tsa hlahisa resonance e bitswang localized surface plasmon resonance (LSPR). LSPR e etsahala ha tshimo ya lesedi e susumetsa dielektrone tsa conduction ho etsa dipoles (kapa di-multipole) tse sisinyehang ho tsamaisana le maqhubu a lesedi.
Bakeng sa li-nanoparticles tse nyane (radius e nyane haholo ho feta bolelele ba wavelength), mokhoa oa quasi-static o atisa ho sebelisoa. Pono e bonolo ea dipole ea karoloana e chitja ka har'a dielectric medium \(\varepsilon_d\) e etsahala hoo e ka bang ha:
\[
\text{Re}[\varepsilon_m(\omega)] \approx -2\varepsilon_d
\]
Sebakeng sa resonance, li-nanoparticles li hlahisa:
– keketseho e kgolo haholo ya haufi le tshimo,
– ho monya le ho hasanya lesedi ka matla,
– ho ba le kutlo e phahameng liphetohong tse hlahang ho refractive index ea tikoloho.
Ke ka lebaka leo LSPR e sebelisoang haholo bakeng sa li-sensor tsa lik'hemik'hale le li-biosensor, mohlala, ho lemoha ho tlamahana ha limolek'hule ka liphetoho litlhōrōng tsa resonance spectrum.
6. Haufi le tšimo, khatello ea leseli, le moeli oa phatloho
E 'ngoe ea lintho tse hohelang plasmonics ke bokhoni ba eona ba ho feta moeli oa diffraction oa optics ea khale. Ho optics e tloaelehileng, tlhokomelo ea leseli e lekanyelitsoe ho hoo e ka bang \(\sim \lambda/2\). Leha ho le joalo, mekhoa ea plasmon (SPP le LSPR) e ka "hatella" matla a motlakase libakeng tse nyane haholo, esita le mashome a li-nanometer kapa ka tlase ho moo, hobane tšimo e tlamiloeng holim'a metsi e na le karolo e kholo ea momentum (maqhubu a phahameng a sebaka).
Tšimo e haufi ea plasmonic le eona e bola kapele ha sebaka se le hole, kahoo tšebelisano-'moho e sebakeng se le seng haholo. Sena se bohlokoa bakeng sa:
– spectroscopy e ntlafaditsweng tshimong (mohlala, SERS: ho hasanya ha Raman ho ntlafaditsweng hodima bokahodimo),
– keketseho ea tlhahiso ea mosi (phello ea Purcell) ho li-emitters tsa quantum,
– di-optics tse seng tsa mola o otlolohileng ho nanoscale.
7. Tahlehelo le bolelele ba ho kheloha
Leha plasmonics e dumella ho hodisa tshimo le kgatello ya lesedi, tahlehelo ke phephetso e kgolo. Tahlehelo e tswa ho:
– ohmic damping: matla a tšimo a fetoloa mocheso ka har'a tšepe,
– ho hasana ka lebaka la ho ba thata kapa ho ba le matheba a bokaholimo,
– tahlehelo ea mahlaseli ho li-nanoparticles (haholo-holo ha boholo bo ntse bo eketseha hoo ho hasana ho eketsehang).
Bakeng sa li-SPP tse ho li-interface tse bataletseng, tahlehelo ena e baka hore amplitude e fokotsehe ho latela tataiso ea ho ata, e leng se fellang ka bolelele ba ho ata bo lekanyelitsoeng. Ho LSPRs, tahlehelo e khetholla bophara ba tlhoro ea resonance: ha tahlehelo e le kholoanyane, resonance e ba kholoanyane (Q-factor e tlase) le phaello e fokotsehileng ea tšimo.
Maiteko a ho fokotsa tahlehelo a kenyeletsa kgetho ya thepa (Ag hangata e na le tahlehelo e tlase ho feta Au leseling le bonahalang), moralo wa jeometri, ho kopanya ka dielectric tse nang le index e phahameng, esita le tshebediso ya thepa e meng e kang aluminium (UV), koporo, nitride (TiN), kapa graphene (haholo-holo bakeng sa bohareng ba IR ho isa ho THz).
8. Ho kopanya le ho kopanya mokhoa oa plasmonic
Meahong e rarahaneng—e kang dimers tsa nanoparticle, nanoantennas, kapa nanogaps—mekhoa ea plasmon e ka sebelisana 'moho' me ea theha mekhoa e mecha, e tšoanang le mohopolo oa ho kopanya orbital k'hemistri. Ha li-nanoparticles tse peli li atametsoa haufi-ufi, tšimo e ka ba kholo haholo (sebaka se chesang), e leng se thusang haholo bakeng sa ho lemoha SERS le molek'hule e le 'ngoe.
Ho phaella moo, di-plasmone di ka kopana le di-exciton ka hara di-semiconductor kapa dimolek'hule, e leng se fellang ka diketsahalo tse matla tsa ho kopanya le ho thehwa ha di-polariton tse kopantsweng. Sena se bohlokwa bakeng sa taolo ya mosi, photochemistry ya tataiso, le disebediswa tsa quantum optical.
9. Litaelo tsa lits'ebetso le lipatlisiso
E hlomelitsoe ka motheo oa khopolo-taba o kaholimo, plasmonics e sebelisoa lits'ebetsong tse fapaneng:
– Li-biosensor le li-refractive index sensor tse thehiloeng ho LSPR kapa SPP,
– SERS bakeng sa tlhahlobo ea lik'hemik'hale tse nang le kutlo e matla haholo,
– Photonics e kopantsoeng le li-waveguide tsa plasmonic bakeng sa miniaturization,
– Ho futhumatsa ka photothermal (ho futhumatsa sebakeng seo) bakeng sa kalafo, catalysis, kapa microprocessing,
– Metasurfaces ea plasmonic bakeng sa ho laola karolo ea leseli le polarization.
Ho ya pele, phephetso ya bohlokwa e tla ba ho leka-lekanya kgatello ya tshimo le tahlehelo ya matla. Diphuputso di boetse di leba thepa e ntjha, dibopeho tsa plasmonic-dielectric tse kopantsweng, le kopanyo le theknoloji ya semiconductor le disebediswa tsa quantum.
Ho koala
Motheo oa khopolo-taba oa fisiks ea plasmonic o thehiloe karabelong e kopaneng ea lielektrone tse lokolohileng ka har'a litšepe ho ea masimong a motlakase, e hlalosoang ka botlalo ke permittivity e rarahaneng le mohlala oa Drude. Ho tsoa ho sena ho hlahile mohopolo oa li-plasmon tsa holim'a metsi—ka bobeli li-SPP libakeng tse bataletseng le li-LSPR ka har'a li-nanoparticles—tse nolofalletsang ho holisoa ha haufi le tšimo le khatello ea leseli ka har'a nanoscale. Leha li lekanyelitsoe ke tahlehelo ea thepa, li-plasmonics li ntse li le tšimo e mafolofolo haholo hobane e kopanya li-optics, saense ea thepa le nanotechnology ho hlahisa lisebelisoa le mekhoa ea ho lekanya ka kutloelo-bohloko le qeto e ke keng ea fihlelloa ke li-optics tse tloaelehileng.
