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tan-nanoparticles fidda

Nanopartiċelli fidda huma nanopartiċelli ta 'fidda ta' bejn 1 nm u 100 nm fid-daqs. [1] Filwaqt li ta 'spiss deskritti bħala "fidda" xi wħud huma magħmula minn persentaġġ kbir ta' ossidu tal-fidda minħabba l-proporzjon kbir tiegħu minn atomi tal-fidda wiċċ to-ingrossa. Bosta forom ta 'nanopartiċelli jistgħu jiġu mibnija skond l-applikazzjoni fil-idejn. Komunement użati huma nanopartiċelli fidda sferiċi iżda djamant, folji ottagonali u rqaq huma wkoll popolari. [1]

Erja tal-wiċċ estremament kbar jippermetti l-koordinazzjoni ta 'numru kbir ta' ligandi . Il-proprjetajiet tan-nanopartiċelli fidda applikabbli għal trattamenti tal-bniedem huma taħt investigazzjoni fi studji tal-laboratorju u l-annimali, il-valutazzjoni tal-effikaċja potenzjali, tossiċità, u l-ispejjeż.

metodi sintetiċi

Kimika Wet [ editja ]

Il-metodi l-aktar komuni għall-sinteżi tan-nanoparticles jaqgħu taħt il-kategorija tal-kimika imxarrab, jew il nucleation ta 'partiċelli fi soluzzjoni. Din il nucleation iseħħ meta kumpless jone tal-fidda, normalment Agno 3 jew AgClO 4, huwa mnaqqas għal kollojde tal-fidda fil-preżenza ta ' aġent li jnaqqas . Meta ż-żidiet konċentrazzjoni biżżejjed, jonji maħlula fidda metalliku jorbtu flimkien biex jiffurmaw wiċċ stabbli. Il-wiċċ huwa b'mod enerġetiku sfavorevoli meta l klusters hu żgħir, minħabba li l-enerġija miksuba billi titnaqqas il-konċentrazzjoni ta 'partiċelli maħlula mhux daqshekk għolja daqs l-enerġija mitlufa mill-ħolqien wiċċ ġdid. [2] Meta l-raggruppament jilħaq ċertu daqs, magħrufa bħala l-raġġ kritika, din issir enerġetiku favorevoli, u b'hekk stabbli biżżejjed li jkompli jikber. Din il nukleu jibqa 'fir-sistema u tikber kif atomi tal-fidda aktar diffużi permezz-soluzzjoni u jagħtu lill-wiċċ [3] Meta l-konċentrazzjoni maħlula tal-fidda atomika jonqos biżżejjed, ma jkunx aktar possibbli għall-atomi biżżejjed biex torbot flimkien biex jiffurmaw stabbli nukleu. Fuq dan il-limitu nucleation, in-nanopartiċelli ġodda tieqaf jiġu ffurmati, u l-fidda maħlul jifdal hija assorbita mill diffużjoni fil-nanopartiċelli li qed jikbru fis-soluzzjoni.

Peress li l-partiċelli jikbru, molekuli oħra fis-soluzzjoni ixerred u jagħtu lill-wiċċ. Dan il-proċess jistabbilizza l-enerġija wiċċ tal-joni tal-fidda partiċelli u blokki ġdid milli jilħaq il-wiċċ. Il-qbid ta 'dawn l-aġenti li jiffissaw limitu massimu / stabilizzanti inaqqas u eventwalment jieqaf it-tkabbir tal-partiċella. [4] L-ligandi capping aktar komuni huma ċitrat tat-trisodju u polivinilpirrolidon (PVP), iżda ħafna oħrajn huma wkoll użati f'kondizzjonijiet varji sabiex jiġu sintetizzati partikoli partikolari d-daqsijiet, forom, u l-proprjetajiet tal-wiċċ. [5]

Hemm ħafna metodi differenti sinteżi wet, inkluż l-użu ta 'zokkor li jnaqqas, it-tnaqqis ċitrat, it-tnaqqis permezz borohydride sodju, [6], ir-reazzjoni mera tal-fidda, [7] il-proċess polyol, [8] tkabbir medjata minn żerriegħa, [9], u tkabbir dawl medjata. [10] Kull wieħed minn dawn il-metodi, jew kombinazzjoni ta 'metodi, se joffri gradi ta' kontroll differenti fuq l-distribuzzjoni tad-daqs kif ukoll distribuzzjonijiet ta 'arranġamenti ġeometriċi tal-tan-nanoparticles. [11]

A ġdida, teknika wet-kimika promettenti ħafna nstab mill Elsupikhe et al. (2015). [12] Dawn żviluppaw sinteżi aħdar ultrasonically assistiti. Taħt ultrasound trattament, nanopartiċelli fidda (AgNP) huma sintetizzati bil κ-carrageenan bħala stabilizzatur naturali. Ir-reazzjoni hija mwettqa f'temperatura ambjentali u tipproduċi nanopartiċelli fidda bi struttura tal-kristall FCC mingħajr impuritajiet. Il-konċentrazzjoni ta κ-Carrageenan huwa użat biex jinfluwenzaw partikola distribuzzjoni tad-daqs tal-AgNPs. [13]

Tnaqqis monosaccharide [ editja ]

Hemm ħafna modi nanopartiċelli fidda jista 'jiġi sintetizzati; Metodu wieħed huwa permezz monosaccharides . Dan jinkludi glukosju , fruttosju , maltosju , maltodextrin , eċċ, imma mhux sukrożju . Huwa wkoll metodu sempliċi biex inaqqsu joni tal-fidda lura lill nanopartiċelli fidda kif normalment jinvolvi proċess ta 'pass wieħed ,. [14] Kien hemm metodi li indikat li dawn zokkor li jnaqqas huma essenzjali għall-formazzjoni ta 'nanopartiċelli fidda. Bosta studji indikaw li dan il-metodu ta 'sinteżi aħdar, speċifikament bl-użu Cacumen estratt platycladi, ippermetta t-tnaqqis tal-fidda. Barra minn hekk, id-daqs tal-nanopartiċelli setgħu jiġu kkontrollati skond il-konċentrazzjoni tal-estratt. L-istudji jindikaw li l-konċentrazzjonijiet ogħla korrelati għal numru akbar ta 'nanopartiċelli. [14] nanopartiċelli iżgħar ġew iffurmati fil għoljin pH livelli minħabba l-konċentrazzjoni ta 'l-monosaccharides.

Metodu ieħor ta 'sinteżi tan-nanoparticles fidda jinkludi l-użu ta' zokkor bil-lamtu alkali u nitrat tal-fidda li jnaqqas. Il zokkor li jnaqqas għandhom liberu aldeide u keton gruppi, li jippermettulhom li jkunu ossidizzat fi gluconate . [15] L-monosaccharide għandu jkollu grupp ketone ħieles minħabba sabiex jaġixxi bħala aġent li jnaqqas l-ewwel jgħaddi tautomerization . Barra minn hekk, jekk il-aldeidi huma marbuta, se tiġi mwaħħla fil-forma ċiklika u ma jistax jaġixxi bħala aġent li jirriduċi. Per eżempju, il-glukożju għandha aldeide grupp funzjonali li hu kapaċi jnaqqas cations fidda għall-atomi tal-fidda u mbagħad ossidizzat għal glukoniku aċidu . [16] Ir-reazzjoni għall-zokkor li għandu jiġi ossidizzat iseħħ f'soluzzjonijiet milwiema. L-aġent capping huwa wkoll mhux preżenti meta msaħħna.

Tnaqqis ċitrat [ editja ]

Kmieni, u komuni ħafna, metodu għall-sintesi nanopartiċelli fidda huwa t-tnaqqis ċitrat. Dan il-metodu ġie l-ewwel irreġistrati mill MC Lea, li pproduċiet b'suċċess kollojde tal-fidda stabbilizzat-ċitrat fl-1889 [17] tnaqqis Citrate jinvolvi t-tnaqqis ta 'partiċella sors fidda, normalment Agno 3 jew AgClO 4, li kollojde tal-fidda bl-użu taċ-ċitrat tat-trisodju , Na 3 C 6 H 5 O 7. [18] Is-sinteżi huwa normalment imwettaq f'temperatura elevata (~ 100 ° C) li jimmassimizzaw l-monodispersity (uniformità fid kemm daqs u forma) tal-partiċella. F'dan il-metodu, il-jone ċitrat tradizzjonalment taġixxi kemm bħala l-aġent tnaqqis u l-ligand capping, [18] u għalhekk jagħmilha proċess utli għall-produzzjoni AgNP minħabba l-faċilità relattiva tiegħu u l-ħin qasir għar-reazzjoni. Madankollu, il-partiċelli fidda iffurmati jistgħu juru distribuzzjonijiet tad-daqs wesgħin u jiffurmaw diversi ġeometriji partiċelli differenti simultanjament. [17] Iż-żieda ta 'aġenti li jnaqqsu aktar b'saħħithom mal-reazzjoni hija spiss użata biex sintetizzati partiċelli ta' daqs u forma aktar uniformi. [18]

Tnaqqis permezz borohydride sodju [ editja ]

Is-sinteżi tal-nanopartiċelli fidda minn borohydride sodju (NABH 4) tnaqqis iseħħ bir-reazzjoni li ġejja: [19]

Ag + + BH 4 - + 3H 2 O → Ag 0 + B (OH) 3 + 3.5H 2

L-atomi tal-metall mnaqqsa se jiffurmaw nuklei tan-nanoparticles. B'mod ġenerali, dan il-proċess huwa simili għall-metodu tnaqqis 'il fuq bl-użu taċ-ċitrat. Il-benefiċċju ta 'użu borohydride sodju tiżdied monodispersity tal-popolazzjoni tal-partiċelli finali. Ir-raġuni għall-monodispersity miżjuda meta jużaw NABH 4 huwa li din hija t-tnaqqis b'saħħtu aġent milli ċitrat. L-impatt tat-tnaqqis qawwa aġent jista 'jidher billi jispezzjona dijagramma Lamer li jiddeskrivi l nucleation u t-tkabbir tan-nanopartiċelli. [20]

Meta nitrat tal-fidda (Agno 3) huwa mnaqqas minn aġent li jnaqqas dgħajfa bħall ċitrat, ir-rata tat-tnaqqis hija aktar baxxa li jfisser li nuklei ġodda huma jiffurmaw u nuklei qodma qed jikbru fl-istess ħin. Din hija r-raġuni li r-reazzjoni ċitrat għandu monodispersity baxx. Minħabba NABH 4 huwa t-tnaqqis aġent ferm aktar b'saħħtu, il-konċentrazzjoni ta 'nitrat tal-fidda huwa mnaqqas b'mod mgħaġġel li tqassar iż-żmien li matulu forma nuklei ġdida u jikbru fl-istess ħin jirrendu popolazzjoni monodispersed ta nanopartiċelli fidda.

Partiċelli iffurmati minn tnaqqis għandu jkollu uċuħ tagħhom stabbilizzata sabiex jipprevjenu agglomerazzjoni partiċella mhux mixtieqa (meta partiċelli multipli bonds flimkien), it-tkabbir, jew jiħraxu f'sens. Il-forza li tmexxi għall dawn il-fenomeni huwa l-minimizzazzjoni ta 'l-enerġija tal-wiċċ (nanopartikuli jkollha wiċċ kbir għall-proporzjon volum). Din it-tendenza li tnaqqas l-enerġija wiċċ fis-sistema jistax jiġi nnewtralizzat billi żżid speċi li se assorbiment għall-wiċċ ta 'l-nanopartiċelli u jbaxxi l-attività tal-wiċċ tal-partiċelli u b'hekk jiġi evitat agglomerazzjoni partiċella skond it-teorija DLVO u l-prevenzjoni tat-tkabbir billi jokkupaw postijiet ta' konnessjoni għal metall atomi. speċi kimiċi li assorbiment għall-wiċċ tan-nanopartiċelli huma msejħa ligandi. Uħud minn dawn wiċċ speċi istabbilizzar huma: NABH 4 f'ammonti kbar, [19] poli (pyrrolidone tal-vinil) (PVP), [21] sulfat dodesil tas-sodju (SDS), [19] [21] u / jew thiol dodecane. [22]

Ladarba l-partiċelli ġew iffurmati f'soluzzjoni iridu jkunu separati u miġbura. Hemm diversi metodi ġenerali biex jitneħħew nanopartiċelli mit soluzzjoni, inkluż evaporazzjoni l-fażi solvent [22] jew iż-żieda ta 'sustanzi kimiċi għas-soluzzjoni li tbaxxi l-tidwib tal-nanopartiċelli fis-soluzzjoni. [23] Iż-żewġ metodi ġġiegħel lill-preċipitazzjoni ta 'l-nanopartiċelli.

Proċess polyol [ editja ]

Il polyol proċess huwa metodu partikolarment utli għaliex jagħti livell għoli ta 'kontroll fuq kemm id-daqs u l-ġeometrija ta' l-nanopartiċelli li jirriżultaw. B'mod ġenerali, is-sinteżi polyol tibda bil-tisħin ta 'kompost polyol bħal ethylene glycol, 1,5-pentanediol, jew glycol7 1,2-propilen. Ag + speċi u aġent capping huma miżjuda (għalkemm il-polyol nnifisha hija wkoll ta 'spiss l-aġent capping). Il + ispeċi Ag huwa mbagħad jitnaqqas bl-polyol tan-nanopartiċelli kollojde. [24] Il-proċess polyol hija sensittiva ħafna għal kundizzjonijiet ta 'reazzjoni bħat-temperatura, l-ambjent kimiċi, u l-konċentrazzjoni ta' sottostrati. [25] [26] Għalhekk, billi jbiddlu dawn il-varjabbli, diversi daqsijiet u ġeometriji jistgħu jiġu magħżula għall bħalma huma kważi-isferi, piramidi, sferi, u wajers. [11] Studju ulterjuri eżaminat il-mekkaniżmu għal dan il-proċess kif ukoll ġeometriji taħt kondizzjonijiet ta 'reazzjoni differenti li jirriżulta f'aktar dettall. [8] [27]

Tkabbir medjata żerriegħa [ editja ]

tkabbir medjata żerriegħa huwa metodu sintetiku li fih żgħar, nuklei stabbli huma mkabbra f'ambjent kimika separata għal daqs mixtieq u forma. Metodi medjat minn żerriegħa jikkonsistu f'żewġ stadji differenti: nucleation u t-tkabbir. Varjazzjoni ta 'ċerti fatturi fil-sintesi (eż ligand, ħin nucleation, tnaqqis aġent, eċċ), [28] tista' tikkontrolla l-daqs finali u l-forma ta 'nanopartiċelli, tagħmel it-tkabbir medjata minn żerriegħa approċċ sintetiku popolari għall-kontroll morfoloġija ta nanopartiċelli.

L-istadju nucleation ta 'tkabbir medjat minn żerriegħa tikkonsisti-tnaqqis tal-jonji tal-metall fi prekursur ta' atomi tal-metall. Sabiex tiġi kkontrollata l distribuzzjoni tad-daqs taż-żrieragħ, il-perjodu ta 'nucleation għandu jsir qasir għall monodispersity. Il-mudell Lamer juri dan il-kunċett. [29] Żrieragħ tipikament jikkonsistu nanopartiċelli żgħar, stabbilizzati permezz ta ' ligand . Ligandi huma żgħar, molekuli normalment organiċi li jorbtu għall-wiċċ ta 'partiċelli, il-prevenzjoni żrieragħ mit-tkabbir ulterjuri. Ligandi huma meħtieġa minħabba li jżidu l-ostaklu tal-enerġija tal-koagulazzjoni, il-prevenzjoni agglomerazzjoni. Il-bilanċ bejn il-forzi attraenti u repulsive fi ħdan soluzzjonijiet kollojdali jistgħu jiġu mmudellati mill -teorija DLVO . [30] ligand affinità ta 'rabta, u selettività jistgħu jintużaw biex jikkontrollaw forma u t-tkabbir. Għal sinteżi żerriegħa, ligand b'kapaċitajiet medji jew affinità baxxa għandhom jingħażlu sabiex jippermettu l-iskambju matul il-fażi ta 'tkabbir.

It-tkabbir ta 'nanoseeds jinvolvi t-tqegħid l-żrieragħ f'soluzzjoni tkabbir. Is-soluzzjoni tat-tkabbir teħtieġ konċentrazzjoni baxxa ta 'prekursur tal-metall, ligandi li se faċilment jibdlu ligandi żerriegħa preexisting, u konċentrazzjoni dgħajfa jew baxxa ħafna tat-tnaqqis aġent. L-aġent jnaqqsu ma għandhom ikunu b'saħħithom biżżejjed biex inaqqsu prekursur metall fis-soluzzjoni tat-tkabbir fin-nuqqas ta 'żrieragħ. Inkella, is-soluzzjoni tat-tkabbir ser tifforma siti ġodda nucleation minflok dejjem tikber fuq dawk preexisting (żrieragħ). [31] It-tkabbir huwa r-riżultat ta 'l-kompetizzjoni bejn l-enerġija wiċċ (li jżid b'mod sfavorevoli ma' tkabbir) u l-enerġija bl-ingrossa (li tonqos b'mod favorevoli ma 'tkabbir). Il-bilanċ bejn il-energetics ta 'tkabbir u dissoluzzjoni hija r-raġuni għat-tkabbir uniformi biss fuq żrieragħ preexisting (u l-ebda nucleation ġdid). [32] It-tkabbir iseħħ biż-żieda ta 'atomi tal-metall mill-soluzzjoni tat-tkabbir għall-żrieragħ, u l-iskambju ligand bejn il ligandi tkabbir (li għandhom affinità bonding ogħla) u l-ligandi żerriegħa. [33]

Firxa u d-direzzjoni tat-tkabbir jistgħu jkunu kkontrollati minn nanoseed, il-konċentrazzjoni ta 'prekursur tal-metall, ligand, u kondizzjonijiet ta' reazzjoni (sħana, pressjoni, eċċ). [34] Il-kontroll kondizzjonijiet stojkjometriċi 'soluzzjoni tkabbir jikkontrolla d-daqs aħħari ta' partiċella. Per eżempju, konċentrazzjoni baxxa ta 'żrieragħ tal-metall għall prekursur metall fis-soluzzjoni tat-tkabbir se jipproduċi partiċelli akbar. aġent capping ġie muri li tikkontrolla d-direzzjoni tat-tkabbir u b'hekk forma. Ligandi jistgħu jkunu jvarjaw affinitajiet għal jorbot madwar partiċella. Differenzjali mhux obbligatorji f'perijodu ta 'partiċella jista' jirriżulta fi tkabbir differenti madwar partiċella. Dan jipproduċi partiċelli anisotropiċi ma 'forom nonspherical inklużi priżmi, kubi, u vireg. [35] [36]

Tkabbir dawl medjat [ editja ]

sinteżi dawl medjati ġew ukoll mistħarrġa fejn dawl tista 'tippromwovi formazzjoni varji morphologies tan-nanoparticles fidda. [10] [37]

Reazzjoni mera tal-fidda [ editja ]

Ir-reazzjoni mera tal-fidda tinvolvi l-konverżjoni tan-nitrat tal-fidda li Ag (NH3) OH. Ag (NH3) OH wara jitnaqqas in kollojde tal-fidda permezz ta 'aldehyde fih molekola bħal zokkor. Ir-reazzjoni mera tal-fidda huwa kif ġej:

2 (Ag (NH 3) 2) + + RCHO + 2OH - → RCOOH + 2Ag + 4NH 3. [38]

Id-daqs u forma tal-nanopartiċelli li jiġu prodotti huma diffiċli biex tikkontrolla u sikwit ikollhom distribuzzjonijiet wiesgħa. [39] Madankollu, dan il-metodu spiss jintuża biex tapplika kisi irqaq ta 'partiċelli fidda fuq uċuħ u aktar studju fil-produzzjoni ta aktar uniformi nanopartiċelli daqs qed isir. [39]

Impjantazzjoni jonika [ editja ]

Ion impjantazzjoni ġiet użata biex jinħolqu nanopartiċelli fidda inkorporati fil -ħġieġ , tal-polyurethane , silikon , tal-polyethylene , u poly (methyl methacrylate) . Partiċelli huma inkorporati fil-sottostrat permezz ta 'bumbardament b'vultaġġi aċċellerazzjoni għoli. Fuq b'densità fiss kurrent tar-raġġ ta 'joni sa ċertu valur, id-daqs tal-nanopartiċelli fidda integrati tkun instabet li tkun monodisperse fi ħdan il-popolazzjoni, [40] wara li tkun osservata biss żieda fil-konċentrazzjoni tal-jone. Instab Żieda oħra fl-doża raġġ joniku biex jitnaqqas kemm id-daqs tan-nanoparticles u d-densità fit-sottostrat mira, filwaqt raġġ ta 'joni li jopera b'vultaġġ aċċellerazzjoni għoli b'densità kurrent li tiżdied gradwalment nstabet li jirriżultaw f'żieda gradwali fil id-daqs tan-nanoparticles. Hemm mekkaniżmi jikkompetu ftit li jistgħu jirriżultaw fit-tnaqqis fid-daqs tan-nanoparticles; qerda ta 'programmi nazzjonali dwar kolliżjoni, sputtering tal-wiċċ tal-kampjun, il-fużjoni tal-partiċelli waqt it-tisħin u dissoċjazzjoni. [40]

Il-formazzjoni ta 'nanopartiċelli integrati hija kumplessa, u kollha tal-parametri li jikkontrollaw u fatturi għadhom ma ġewx investigati. simulazzjoni kompjuter għadu diffiċli peress li tinvolvi proċessi ta 'diffużjoni u clustering, madankollu jista' jinqasam fi ftit sottoproċessi differenti ftit bħal impjantazzjoni, tixrid, u t-tkabbir. Mal-impjantazzjoni, joni tal-fidda se tilħaq fond differenti fi ħdan l-sottostrat li approċċi distribuzzjoni Gaussian mal-medja ċċentrata fuq X-fond. kondizzjonijiet ta 'temperatura għolja matul l-istadji inizjali ta' impjantazzjoni se jżidu l-impurità tixrid fil-substrat u bħala riżultat jillimitaw l-saturazzjoni jone jkollu effett, li hija meħtieġa għall nucleation tan-nanoparticles. [41] Kemm il-temperatura impjant u raġġ ta 'joni densità ta' kurrent huma kruċjali għall-kontroll sabiex jiksbu daqs tan-nanoparticles monodisperse u d-distribuzzjoni fond. A densità ta 'kurrent baxx tista' tintuża biex jikkumbatti l-aġitazzjoni termali mir-raġġ ta 'joni u buildup ta' ħlas tal-wiċċ. Wara impjantazzjoni fuq il-wiċċ, l-kurrenti ta 'raġġi jistgħu jitqajmu bħala l-konduttività wiċċ se jiżdied. [41] Ir-rata li biha l-impuritajiet diffużi qtar malajr wara l-formazzjoni ta 'l-nanopartiċelli, li jaġixxu bħala nassa jone mobbli. Dan jissuġġerixxi li l-bidu tal-proċess impjantazzjoni huwa kritiku għall-kontroll tal-ispazjar u l-fond ta 'l-nanopartiċelli li jirriżultaw, kif ukoll il-kontroll tad-densità raġġ temperatura sottostrat u jone. Il-preżenza u n-natura ta 'dawn il-partiċelli jistgħu jiġu analizzati bl-użu diversi strumenti ispettroskopija u mikroskopija. [41] nanopartiċelli sintetizzati fil-sottostrat juru resonanzi Plasmon wiċċ kif muri minn strixxi ta 'assorbiment karatteristika; dawn il-karatteristiċi jgħaddu bidliet spettrali skond id-daqs tan-nanoparticles u asperities wiċċ, [40] madankollu l-proprjetajiet ottiċi wkoll jiddependu b'mod qawwi fuq il-materjal sottostrat tal-kompożitu.

Sinteżi Bijoloġika [ editja ]

Is-sinteżi bijoloġika tan-nanopartiċelli pprovda mezz għal tekniki mtejba meta mqabbla mal-metodi tradizzjonali li jitolbu l-użu ta 'aġenti li jnaqqsu ħsara bħal borohydride sodju . Ħafna minn dawn il-metodi tista 'ttejjeb impronta ambjentali tagħhom billi tissostitwixxi dawn l-aġenti li jnaqqsu relattivament qawwija. Il-problemi bil-produzzjoni kimika tan-nanopartiċelli fidda huwa normalment jinvolvi spejjeż għoljin u l-lonġevità tal-partiċelli hija qasira għexet minħabba aggregazzjoni. Il harshness tal-metodi kimiċi standard qajmet l-użu ta 'użu organiżmi bijoloġiċi li tnaqqas joni tal-fidda fis-soluzzjoni fis nanopartiċelli kollojdali. [42] [43]

Barra minn hekk, il-kontroll preċiż fuq forma u d-daqs huwa vitali matul is-sintesi tan-nanoparticles peress li l-proprjetajiet terapewtiċi programmi nazzjonali huma intimament dipendenti fuq dawn il-fatturi. [44] Għalhekk, il-fokus primarju ta 'riċerka fis-sinteżi bijoġeniku huwa fl-iżvilupp ta' metodi li konsistentament jirriproduċu programmi nazzjonali bi proprjetajiet preċiżi. [45] [46]

Fungi u batterji [ editja ]

Rappreżentazzjoni ġenerali tal-sinteżi u l-applikazzjonijiet tan-nanopartiċelli fidda bijoġenetikament sintetizzati jużaw estratt tal-pjanti.

Batterjali u fungali sintesi tan-nanopartiċelli huwa prattiku minħabba batterji u fungi huma faċli biex jimmaniġġaw u jistgħu jiġu modifikati ġenetikament bil-faċilità. Dan jipprovdi mezz biex tiżviluppa bijomolekuli li jista sintetizzati AgNPs ta 'forom u daqsijiet li jvarjaw fid rendiment għoli, li huwa fuq quddiemnett ta' sfidi attwali fil sintesi tan-nanoparticles. Razez fungali bħal Verticillium u razez ta 'batterji bħal K. pneumoniae jistgħu jintużaw fis-sintesi ta' nanopartiċelli fidda. [47] Meta l-fungus / batterji huwa miżjud ma 'soluzzjoni, bijomassa proteina huwa rilaxxat fil-soluzzjoni. [47] Elettroni donazzjoni residwi bħal tryptophan u tyrosine jnaqqsu joni tal-fidda fis-soluzzjoni kontribwit mir nitrat tal-fidda. [47] Dawn il-metodi jkunu nstabu li effettivament joħolqu nanopartiċelli monodisperse stabbli mingħajr l-użu ta 'aġenti tat-tnaqqis ta' ħsara.

Metodu Instab li jitnaqqas joni tal-fidda bl-introduzzjoni ta 'l-fungus Fusarium oxysporum . Il nanopartiċelli ffurmati f'dan il-metodu jkollhom firxa daqs bejn 5 u 15 nm u jikkonsistu fidda Hydrosol . It-tnaqqis ta 'l-nanopartiċelli fidda huwa maħsub li ġejjin minn proċess u fidda enżimatiċi nanopartiċelli li jiġu prodotti huma estremament stabbli minħabba l-interazzjonijiet ma' proteini li huma mneħħija mill-fungi.

Batterju misjuba fil-minjieri tal-fidda, Pseudomonas stutzeri AG259, kienu f'pożizzjoni li jibni partiċelli fidda fil-forom ta 'triangoli u hexagons. Id-daqs ta 'dawn in-nanopartiċelli kellu firxa kbira fid-daqs u xi wħud minnhom laħaq daqsijiet akbar milli l-nanoskala soltu b'daqs ta' 200 nm. Il nanopartiċelli fidda kienu jinstabu fl-matriċi organiku tal-batterji. [48]

Aċidu lattiku batterji li jipproduċu jkunu ġew użati biex jipproduċu nanopartiċelli fidda. Il-batterji Lactobacillus spp., Pentosaceus Pediococcus, Enteroccus faeciumI, u Lactococcus garvieae nstabu li jkunu jistgħu jnaqqsu joni tal-fidda fis nanopartiċelli fidda. Il-produzzjoni ta 'l-nanopartiċelli jseħħ fiċ-ċellola mill-interazzjonijiet bejn il-joni tal-fidda u l-komposti organiċi ta' l-ċellula. Instab li l-batterju Lactobacillus fermentum ħolqu l-nanopartiċelli fidda iżgħar b'daqs medju ta '11.2 nm. Instab ukoll li dan batterju prodotta l-nanopartiċelli mal-iżgħar distribuzzjoni tad-daqs u l-nanopartiċelli nstabu aktar fuq barra taċ-ċelloli. Instab ukoll li kien hemm żieda fil- pH żied ir-rata ta 'liema l-nanopartiċelli ġew prodotti u l-ammont ta' partiċelli prodotti. [49]

Pjanti [ editja ]

It-tnaqqis ta 'joni tal-fidda fis-nanopartiċelli fidda ġie wkoll miksuba bl-użu ġeranium weraq. Instab li ż-żieda estratt tal-weraq ġeranium għal soluzzjonijiet tan-nitrat tal-fidda tikkawża joni tal-fidda tagħhom li jitnaqqsu malajr u li l-nanopartiċelli manifatturati huma partikolarment stabbli. Il nanopartiċelli fidda prodotta f'soluzzjoni kellu firxa daqs bejn 16 u 40 nm. [48]

Fi studju ieħor estratti tal-weraq tal-pjanti differenti kienu użati biex inaqqsu joni tal-fidda. Instab li minn Camellia sinensis (tè aħdar), arżnu , persimmon , ginko , Magnolia , u Platanus li l-estratt tal-werqa Magnolia kienet l-aħjar li toħloq nanopartiċelli fidda. Dan il-metodu ħoloq partiċelli ma 'firxa daqs iferrxu ta 15-500 nm, iżda nstab ukoll li d-daqs tal-partiċelli jista' jiġi kkontrollat billi tvarja t-temperatura reazzjoni. Il-veloċità li biha l-jonji tnaqqsu mill-estratt tal-werqa Magnolia kien komparabbli ma 'dawk ta' użu tal-kimiċi li tnaqqas. [42] [50]

L-użu ta 'pjanti, mikrobi, u fungi fil-produzzjoni ta' nanopartiċelli fidda huwa jwassal il-mod għall-produzzjoni aktar ambjentalment sod ta 'nanopartiċelli fidda. [43]

A Metodu ħadra hija disponibbli għall sintesi nanopartiċelli fidda bl-użu Amaranthus gangeticus Linn estratt tal-werqa. [51]

Prodotti u functionalization [ editja ]

protokolli sintetiċi għall-produzzjoni tan-nanoparticles fidda jista 'jiġi mmodifikat biex jipproduċu nanopartiċelli fidda ma ġeometriji mhumiex sferiċi u wkoll biex functionalize nanopartiċelli ma' materjali differenti, bħall-silika. Ħolqien nanopartiċelli fidda ta 'forom differenti u kisi tal-wiċċ tippermetti għall-kontroll akbar fuq proprjetajiet speċifiċi għal daqs tagħhom.

Istrutturi anisotropiċi [ editja ]

nanopartiċelli fidda jista 'jiġi sintetizzat fil-varjetà ta' non-sferiċi (anisotropiċi) forom. Minħabba fidda, bħal metalli nobbli oħra, juri daqs u forma dipendenti effett ottiku magħrufa bħala lokalizzati reżonanza Plasmon wiċċ (LSPR) fin-nanoskala, l-abbiltà li sintetizzati nanopartiċelli Ag fil-forom differenti ferm iżid il-kapaċità li tixgħel imġieba ottika tagħhom. Per eżempju, il-frekwenza li fiha l LSPR sseħħ għal nanopartikuli ta morfoloġija wieħed (eż sfera) se tkun differenti jekk dik l-isfera tinbidel fi forma differenti. Din id-dipendenza forma jippermetti tan-nanoparticles fidda li jesperjenzaw titjib ottika fuq medda ta 'wavelengths differenti, anke billi jżommu id-daqs relattivament kostanti, biss billi jinbidlu għamla tagħha. L-applikazzjonijiet ta 'din l-espansjoni sfruttati forma ta' firxa imġiba ottika milli jiżviluppaw biosensuri aktar sensittivi biex tiżdied il-lonġevità ta 'tessuti. [52] [53]

Nanoprisms triangolari [ editja ]

nanopartiċelli forma trijangulari huma tip canonical ta morfoloġija anisotropiku bil studjati għal kemm deheb u fidda. [54]

Għalkemm jeżistu tekniki differenti ħafna għall-sinteżi nanoprism fidda, diversi metodi jħaddmu approċċ medjat minn żerriegħa, li jinvolvi l-ewwel sintesi żgħar nanopartiċelli fidda (3-5 nm dijametru) li joffru mudell ta 'tkabbir immirata forma fis nanostrutturi triangolari. [55]

Iż-żrieragħ tal-fidda huma sintetizzati bit-taħlit nitrat tal-fidda u sodium citrate f'soluzzjoni milwiema u mbagħad jiżdied rapidament borohydride sodju. nitrat tal-fidda addizzjonali hija miżjuda mas-soluzzjoni żerriegħa f'temperatura baxxa, u l-priżmi huma mkabbra billi bil-mod jitnaqqas il-nitrat tal-fidda żejjed juża l-aċidu askorbiku. [6]

Bl-approċċ medjat il-bidu sa sinteżi nanoprism fidda, selettività ta 'forma waħda fuq ieħor jista parzjalment jiġi kkontrollat mill-ligand capping. Jużaw essenzjalment l-istess proċedura msemmija hawn fuq, iżda li jinbidlu ċitrat biex poli (pyrrolidone tal-vinil) (PVP) rendimenti kubu u nanostrutturi f'għamla ta 'virga minflok nanoprisms trijangulari. [56]

Minbarra l-teknika żerriegħa medjat, nanoprisms fidda jista 'wkoll jiġu sintetizzati bl-użu ta' approċċ medjat ritratt, fejn preexisting nanopartiċelli fidda sferiċi huma trasformati nanoprisms triangolari sempliċiment billi jesponu l-taħlita ta 'reazzjoni għall-intensitajiet għolja ta' dawl. [57]

Nanocubes [ editja ]

nanocubes Silver jistgħu jiġu sintetizzati bl-użu ethylene glycol bħala aġent li jnaqqas u PVP bħala aġent capping, f'reazzjoni sintesi polyol (vide supra). Sinteżi tipiku jużaw dawn ir-reaġenti jinvolvi żżid nitrat tal-fidda frisk u PVP għal soluzzjoni ta 'ethylene glycol imsaħħan f'140 ° C. [58]

Din il-proċedura tista 'attwalment jiġu modifikati sabiex jipproduċu ieħor nanostructure fidda anisotropiku bil, nanowires, bi ftit tippermetti s-soluzzjoni tan-nitrat tal-fidda għall-età qabel ma tużah fis-sinteżi. Billi jippermettu s-soluzzjoni tan-nitrat tal-fidda għall-età, il-nanostructure inizjali jiffurmaw waqt il-sintesi hija kemmxejn differenti minn dik miksuba bil nitrat frisk fidda, li jinfluwenza l-proċess ta 'tkabbir, u għalhekk, il-morfoloġija tal-prodott finali. [58]

Kisi bil-silika [ editja ]

Proċedura ġenerali għall-kisi partiċelli kollojde fil-silika. L-ewwel PVP huwa assorbit fuq il-wiċċ kollojdali. Dawn il-partiċelli huma mqiegħda f'soluzzjoni ta 'ammonja fl-etanol. il partiċella mbagħad jibda jikber biż-żieda ta Si (OET4).

F'dan il-metodu, polivinilpirrolidon (PVP) jiġi maħlul fl-ilma mill ivvibrar u mħallat bil-fidda kollojde partiċelli. [1] tħawwad Attiva jiżgura l-PVP ma assorbiti mal-wiċċ tan-nanoparticles. [1] tiċċentrifugah jifred l-nanopartiċelli PVP miksija li huma mbagħad trasferiti għal soluzzjoni ta ' l-etanol li jkun ċentrifugat ulterjuri u mqiegħda f'soluzzjoni ta' ammonja , etanol u Si (OET 4) (TES). [1] Waqt li tħawwad għal tnax-riżultati siegħa fil- silika qoxra jiġu ffurmati tikkonsisti minn saff madwar ta ' ossidu tas-silikon bi etere rabta disponibbli għall tiżdied il-funzjonalità. [1] li tvarja l-ammont ta 'TES jippermetti għal ħxuna differenti ta' qxur iffurmati. [1] Din it-teknika hija popolari minħabba l-abbiltà li żżid varjetà ta 'funzjonalità għall-wiċċ silika espost.

Uża [ editja ]

Kataliżi [ editja ]

Bl-użu nanopartiċelli fidda għal katalisi ġie jikseb attenzjoni fis-snin riċenti. Għalkemm l-applikazzjonijiet l-aktar komuni huma għal skopijiet mediċinali jew antibatteriċi, nanopartiċelli fidda intwerew li juru katalitiċi redox proprjetajiet għall żebgħat, benżina, monossidu karboniku, u komposti oħra li x'aktarx.

NOTA: Dan il-paragrafu huwa deskrizzjoni ġenerali ta 'proprjetajiet tan-nanoparticles għall kataliżi; mhuwiex esklussiv għall nanopartiċelli fidda. Id-daqs ta 'tan-nanoparticles jiddetermina bil-kbir l-proprjetajiet li juri minħabba l-effetti quantum varji. Barra minn hekk, l-ambjent kimika tal-nanopartiċelli għandha rwol kbir fuq il-proprjetajiet katalitiċi. B'konsiderazzjoni ta 'dan, huwa importanti li wieħed jinnota li eteroġeni katalisi sseħħ mill assorbiment ta' l-ispeċi sustanza reattiva għas-sottostrat katalitiku. Meta polimeri , kumplessi ligandi , jew surfactants jintużaw sabiex ikun evitat coalescence tal-nanopartiċelli, l-abbiltà katalitiku huwa spiss imxekkel minħabba l-kapaċità ta 'assorbiment imnaqqsa. [59] Madankollu, dawn il-komposti jistgħu wkoll jintużaw b'tali mod li l-ambjent kimika ttejjeb il-kapaċità katalitiku.

Sostnuta fuq isferi silika - tnaqqis ta 'żebgħa [ editja ]

Nanopartikuli Silver ġew sintetizzati fuq support ta 'inerti silika sferi. [59] L -appoġġ għandu prattikament l-ebda rwol fil-kapaċità katalitiku u sservi bħala metodu ta 'prevenzjoni coalescence tal-nanopartiċelli fidda fl soluzzjoni kollojdali . Għalhekk, il-nanopartiċelli fidda kienu stabbilizzati u kien possibbli li jintwera l-kapaċità tagħhom li jservu bħala relay elettron għat-tnaqqis ta ' żebgħa minn borohydride sodju . [59] Mingħajr l-katalist tan-nanoparticles fidda, kważi l-ebda reazzjoni sseħħ bejn borohydride sodju u l-żebgħa varji: metilin ikħal , eosin , u tela bengal .

Mesoporous airgel - ossidazzjoni selettiva tal-benżin [ editja ]

Nanopartiċelli fidda appoġġjati fuq airgel huma vantaġġjużi minħabba l-għadd akbar ta ' siti attivi . [60] L-ogħla selettività għall-ossidazzjoni ta ' benżin li fenol kienet osservata fil-mija piż baxx tal-fidda fil-matriċi airgel (1% Ag). Din il ahjar selettività huwa maħsub li jkun riżultat ta 'l-ogħla monodispersity fi ħdan il-matriċi airgel tal-kampjun Ag 1%. Kull soluzzjoni mija piż iffurmata partiċelli ta 'daqs differenti b'wisa' differenti ta 'skala ta' daqs. [60]

Fidda liga - ossidazzjoni sinerġistiku tat-monossidu tal-karbonju [ editja ]

Nanopartiċelli liga au-Ag ġew ippruvati li għandhom effett sinerġistiku fuq il ossidazzjoni ta monossidu tal-karbonju (CO). [61] Waħidha, kull nanopartiċelli pur tal-metall turi attività katalitika fqira ħafna għal CO ossidazzjoni ; flimkien, il-proprjetajiet katalitiċi jitjiebu ħafna. Qed jiġi propost li l-deheb taġixxi bħala 'aġent li jgħaqqad qawwi għall-atomu ossiġnu u l-fidda sservi bħala katalista ossidanti qawwija, għalkemm il-eżatt mekkaniżmu għadu mhux mifhum għal kollox. When synthesized in an Au/Ag ratio from 3:1 to 10:1, the alloyed nanoparticles showed complete conversion when 1% CO was fed in air at ambient temperature. [61] Interestingly, the size of the alloyed particles did not play a big role in the catalytic ability. It is well known that gold nanoparticles only show catalytic properties for CO when they are ~3 nm in size, but alloyed particles up to 30 nm demonstrated excellent catalytic activity – catalytic activity better than that of gold nanoparticles on active support such as TiO 2 , Fe 2 O 3 , etc. [61]

Light-enhanced [ edit ]

Plasmonic effects have been studied quite extensively. Until recently, there have not been studies investigating the oxidative catalytic enhancement of a nanostructure via excitation of its surface plasmon resonance . The defining feature for enhancing the oxidative catalytic ability has been identified as the ability to convert a beam of light into the form of energetic electrons that can be transferred to adsorbed molecules. [62] The implication of such a feature is that photochemical reactions can be driven by low-intensity continuous light can be coupled with thermal energy .

The coupling of low-intensity continuous light and thermal energy has been performed with silver nanocubes. The important feature of silver nanostructures that are enabling for photocatalysis is their nature to create resonant surface plasmons from light in the visible range. [62]

The addition of light enhancement enabled the particles to perform to the same degree as particles that were heated up to 40 K greater. [62] This is a profound finding when noting that a reduction in temperature of 25 K can increase the catalyst lifetime by nearly tenfold, when comparing the photothermal and thermal process. [62]

Biological research [ edit ]

Researchers have explored the use of silver nanoparticles as carriers for delivering various payloads such as small drug molecules or large biomolecules to specific targets. Once the AgNP has had sufficient time to reach its target, release of the payload could potentially be triggered by an internal or external stimulus. The targeting and accumulation of nanoparticles may provide high payload concentrations at specific target sites and could minimize side effects. [63]

Chemotherapy [ edit ]

The introduction of nanotechnology into medicine is expected to advance diagnostic cancer imaging and the standards for therapeutic drug design. [64] Nanotechnology may uncover insight about the structure, function and organizational level of the biosystem at the nanoscale. [65]

Silver nanoparticles can undergo coating techniques that offer a uniform functionalized surface to which substrates can be added. When the nanoparticle is coated, for example, in silica the surface exists as silicic acid. Substrates can thus be added through stable ether and ester linkages that are not degraded immediately by natural metabolic enzymes . [66] [67] Recent chemotherapeutic applications have designed anti cancer drugs with a photo cleavable linker, [68] such as an ortho-nitrobenzyl bridge, attaching it to the substrate on the nanoparticle surface. [66] The low toxicity nanoparticle complex can remain viable under metabolic attack for the time necessary to be distributed throughout the bodies systems. [66] [69] If a cancerous tumor is being targeted for treatment, ultraviolet light can be introduced over the tumor region. [66] The electromagnetic energy of the light causes the photo responsive linker to break between the drug and the nanoparticle substrate. [66] The drug is now cleaved and released in an unaltered active form to act on the cancerous tumor cells. [66] Advantages anticipated for this method is that the drug is transported without highly toxic compounds, the drug is released without harmful radiation or relying on a specific chemical reaction to occur and the drug can be selectively released at a target tissue. [66] [67] [69]

A second approach is to attach a chemotherapeutic drug directly to the functionalized surface of the silver nanoparticle combined with a nucelophilic species to undergo a displacement reaction. For example, once the nanoparticle drug complex enters or is in the vicinity of the target tissue or cells, a glutathione monoester can be administered to the site. [70] [71] The nucleophilic ester oxygen will attach to the functionalized surface of the nanoparticle through a new ester linkage while the drug is released to its surroundings. [70] [71] The drug is now active and can exert its biological function on the cells immediate to its surroundings limiting non-desirable interactions with other tissues. [70] [71]

Multiple drug resistance [ edit ]

A major cause for the ineffectiveness of current chemotherapy treatments is multiple drug resistance which can arise from several mechanisms. [72]

Nanoparticles can provide a means to overcome MDR. In general, when using a targeting agent to deliver nanocarriers to cancer cells, it is imperative that the agent binds with high selectivity to molecules that are uniquely expressed on the cell surface. Hence NPs can be designed with proteins that specifically detect drug resistant cells with overexpressed transporter proteins on their surface. [73] A pitfall of the commonly used nano-drug delivery systems is that free drugs that are released from the nanocarriers into the cytosol get exposed to the MDR transporters once again, and are exported. To solve this, 8 nm nano crystalline silver particles were modified by the addition of trans-activating transcriptional activator (TAT), derived from the HIV-1 virus, which acts as a cell penetrating peptide (CPP). [74] Generally, AgNP effectiveness is limited due to the lack of efficient cellular uptake; however, CPP-modification has become one of the most efficient methods for improving intracellular delivery of nanoparticles. Once ingested, the export of the AgNP is prevented based on a size exclusion. The concept is simple: the nanoparticles are too large to be effluxed by the MDR transporters, because the efflux function is strictly subjected to the size of its substrates, which is generally limited to a range of 300-2000 Da. Thereby the nanoparticulates remain insusceptible to the efflux, providing a means to accumulate in high concentrations. [ citation needed ]

Antimicrobial [ edit ]

Introduction of silver into bacterial cells induces a high degree of structural and morphological changes, which can lead to cell death. As the silver nano particles come in contact with the bacteria, they adhere to the cell wall and cell membrane. [75] Once bound, some of the silver passes through to the inside, and interacts with phosphate-containing compounds like DNA and RNA , while another portion adheres to the sulphur-containing proteins on the membrane. [75] The silver-sulphur interactions at the membrane cause the cell wall to undergo structural changes, like the formation of pits and pores. [76] Through these pores, cellular components are released into the extracellular fluid, simply due to the osmotic difference. Within the cell, the integration of silver creates a low molecular weight region where the DNA then condenses. [76] Having DNA in a condensed state inhibits the cell's replication proteins contact with the DNA. Thus the introduction of silver nanoparticles inhibits replication and is sufficient to cause the death of the cell. Further increasing their effect, when silver comes in contact with fluids, it tends to ionize which increases the nanoparticles bactericidal activity. [76] This has been correlated to the suppression of enzymes and inhibited expression of proteins that relate to the cell's ability to produce ATP. [77]

Although it varies for every type of cell proposed, as their cell membrane composition varies greatly, It has been seen that in general, silver nano particles with an average size of 10 nm or less show electronic effects that greatly increase their bactericidal activity. [78] This could also be partly due to the fact that as particle size decreases, reactivity increases due to the surface area to volume ratio increasing. [ citation needed ]

It has been noted that the introduction of silver nano particles has shown to have synergistic activity with common antibiotics already used today, such as; penicillin G , ampicillin , erythromycin , clindamycin , and vancomycin against E. coli and S. aureus. [79] In medical equipment, it has been shown that silver nano particles drastically lower the bacterial count on devices used. However, the problem arises when the procedure is over and a new one must be done. In the process of washing the instruments a large portion of the silver nano particles become less effective due to the loss of silver ions . They are more commonly used in skin grafts for burn victims as the silver nano particles embedded with the graft provide better antimicrobial activity and result in significantly less scarring of the victim. They also show promising application as water treatment method to form clean potable water. [80]

Silver nanoparticles can prevent bacteria from growing on or adhering to the surface. This can be especially useful in surgical settings where all surfaces in contact with the patient must be sterile. Interestingly, silver nanoparticles can be incorporated on many types of surfaces including metals, plastic, and glass. [81] In medical equipment, it has been shown that silver nano particles lower the bacterial count on devices used compared to old techniques. However, the problem arises when the procedure is over and a new one must be done. In the process of washing the instruments a large portion of the silver nano particles become less effective due to the loss of silver ions . They are more commonly used in skin grafts for burn victims as the silver nano particles embedded with the graft provide better antimicrobial activity and result in significantly less scarring of the victim.These new applications are direct decedents of older practices that used silver nitrate to treat conditions such as skin ulcers. Now, silver nanoparticles are used in bandages and patches to help heal certain burns and wounds. [82]

They also show promising application as water treatment method to form clean potable water. [80] This doesn't sound like much, but water contains numerous diseases and some parts of the world do not have the luxury of clean water, or any at all. It wasn't new to use silver for removing microbes, but this experiment used the carbonate in water to make microbes even more vulnerable to silver. [83] First the scientists of the experiment use the nanopaticles to remove certain pesticides from the water, ones that prove fatal to people if ingested. Several other tests have shown that the silver nanoparticles were capable of removing certain ions in water as well, like iron, lead, and arsenic. But that is not the only reason why the silver nanoparticles are so appealing, they do not require any external force (no electricity of hydrolics) for the reaction to occur. [84]

Consumer Goods [ edit ]

Household applications [ edit ]

There are instances in which silver nanoparticles and colloidal silver are used in consumer goods. Samsung and LG are two major tech companies planning to use antibacterial properties of silver nanoparticles in a multitude of appliances such as air conditioners, washing machines, and refrigerators. [85] For example, both companies claim that the use of silver nanoparticles in washing machines would help to sterilize clothes and water during the washing and rinsing functions, and allow clothes to be cleaned without the need for hot water. [85] [86] The nanoparticles in these appliances are synthesized using electrolysis . Through electrolysis, silver is extracted from metal plates and then turned into silver nanoparticles by a reduction agent. [87] This method avoids the drying, cleaning and re-dispersion processes, which are generally required with alternative colloidal synthesis methods. [87] Importantly, the electrolysis strategy also decreases the production cost of Ag nanoparticles, making these washing machines more affordable to manufacture. [88] Samsung has described the system:

[A] grapefruit-sized device alongside the [washer] tub uses electrical currents to nanoshave two silver plates the size of large chewing gum sticks. Resulting in positively charged silver atoms-silver ions (Ag+)-are injected into the tub during the wash cycle. [88]

It is important to note that Samsung's description of the Ag nanoparticle generating process seems to contradict its advertisement of silver nanoparticles. Instead, the statement indicates that laundry cycles. [87] [88] When clothes are run through the cycle, the intended mode of action is that bacteria contained in the water are sterilized as they interact with the silver present in the washing tub. [86] [88] As a result, these washing machines can provide antibacterial and sterilization benefits on top of conventional washing methods. Samsung has commented on the lifetime of these silver-containing washing machines. The electrolysis of silver generates over 400 billion silver ions during each wash cycle. Given the size of the silver source (two “gum-sized” plate of Ag), Samsung estimates that these plates can last up to 3000 wash cycles. [88]

These plans by Samsung and LG are not overlooked by regulatory agencies. Agencies investigating LG's nanoparticle use include but are not limited to: the US FDA , US EPA , SIAA of Japan, and Korea's Testing and Research Institute for Chemical Industry and FITI Testing & Research Institute. [86] These various agencies plan to regulate silver nanoparticles in appliances. [86] These washing machines are some of the first cases in which the EPA has sought to regulate nanoparticles in consumer goods. LG and Samsung state that the silver gets washed away in the sewer and regulatory agencies worry over what that means for wastewater treatment streams. [88] Currently, the EPA classifies silver nanoparticles as pesticides due to their use as antimicrobial agents in wastewater purification. [85] The washing machines being developed by LG and Samsung do contain a pesticide and have to be registered and tested for safety under the law, particularly the US Federal insecticide, fungicide and rodenticide act. [85] The difficulty, however behind regulating nanotechnology in this manner is that there is no distinct way to measure toxicity. Tim Harper, CEO of nanotechnology consultants Cientifica, explained, "we don't really have the science to prove anything one way or another". [85] The example of these washing machines demonstrates that while nanotechnology using silver nanoparticles in commercial appliances is showing promise, ways to measure toxicity and health hazards to humans, bacteria, or the environment will continue to be hurdle for nanoparticle technology implementation.

Safety [ edit ]

Although silver nanoparticles are widely used in a variety of commercial products, there has only recently been a major effort to study their effects on human health. There have been several studies that describe the in vitro toxicity of silver nanoparticles to a variety of different organs, including the lung, liver, skin, brain, and reproductive organs. [89] The mechanism of the toxicity of silver nanoparticles to human cells appears to be derived from oxidative stress and inflammation that is caused by the generation of reactive oxygen species (ROS) stimulated by either the Ag NPs, Ag ions, or both. [90] [91] [92] [93] [94] For example, Park et al. showed that exposure of a mouse peritoneal macrophage cell line (RAW267.7) to silver nanoparticles decreased the cell viability in a concentration- and time-dependent manner. [93] They further showed that the intracellular reduced glutathionine (GSH), which is a ROS scavenger, decreased to 81.4% of the control group of silver nanoparticles at 1.6 ppm. [93]

Modes of toxicity [ edit ]

Since silver nanoparticles undergo dissolution releasing silver ions, [95] which is well-documented to have toxic effects, [94] [95] [96] there have been several studies that have been conducted to determine whether the toxicity of silver nanoparticles is derived from the release of silver ions or from the nanoparticle itself. Several studies suggest that the toxicity of silver nanoparticles is attributed to their release of silver ions in cells as both silver nanoparticles and silver ions have been reported to have similar cytotoxicity. [92] [93] [97] [98] For example, In some cases it is reported that silver nanoparticles facilitate the release of toxic free silver ions in cells via a "Trojan-horse type mechanism," where the particle enters cells and is then ionized within the cell. [93] However, there have been reports that suggest that a combination of silver nanoparticles and ions is responsible for the toxic effect of silver nanoparticles. Navarro et al. using cysteine ligands as a tool to measure the concentration of free silver in solution, determined that although initially silver ions were 18 times more likely to inhibit the photosynthesis of an algae, Chlamydomanas reinhardtii, but after 2 hours of incubation it was revealed that the algae containing silver nanoparticles were more toxic than just silver ions alone. [99] Furthermore, there are studies that suggest that silver nanoparticles induce toxicity independent of free silver ions. [94] [100] [101] For example, Asharani et al. compared phenotypic defects observed in zebrafish treated with silver nanoparticles and silver ions and determined that the phenotypic defects observed with silver nanoparticle treatment was not observed with silver ion-treated embryos, suggesting that the toxicity of silver nanoparticles are independent of silver ions. [101]

Protein channels and nuclear membrane pores can often be in the size range of 9 nm to 10 nm in diameter. [94] Small silver nanoparticles constructed of this size have the ability to not only pass through the membrane to interact with internal structures but also to be become lodged within the membrane. [94] Silver nanoparticle depositions in the membrane can impact regulation of solutes, exchange of proteins and cell recognition. [94] Exposure to silver nanoparticles has been associated with "inflammatory, oxidative, genotoxic, and cytotoxic consequences"; the silver particulates primarily accumulate in the liver. [102] but have also been shown to be toxic in other organs including the brain. [103] Nano-silver applied to tissue-cultured human cells leads to the formation of free radicals, raising concerns of potential health risks. [104]

  • Allergic reaction: There have been several studies conducted that show a precedence for allerginicity of silver nanoparticles. [105] [106]

  • Argyria and staining: Ingested silver or silver compounds, including colloidal silver , can cause a condition called argyria , a discoloration of the skin and organs.In 2006, there was a case study of a 17-year-old man, who sustained burns to 30% of his body, and experienced a temporary bluish-grey hue after several days of treatment with Acticoat, a brand of wound dressing containing silver nanoparticles. [107] Argyria is the deposition of silver in deep tissues, a condition that cannot happen on a temporary basis, raising the question of whether the cause of the man's discoloration was argyria or even a result of the silver treatment. [108] Silver dressings are known to cause a “transient discoloration” that dissipates in 2–14 days, but not a permanent discoloration. [ citation needed ]

  • Silzone heart valve: St. Jude Medical released a mechanical heart valve with a silver coated sewing cuff (coated using ion beam-assisted deposition) in 1997. [109] The valve was designed to reduce the instances of endocarditis . The valve was approved for sale in Canada, Europe, the United States, and most other markets around the world. In a post-commercialization study, researchers showed that the valve prevented tissue ingrowth, created paravalvular leakage, valve loosening, and in the worst cases explantation. After 3 years on the market and 36,000 implants, St. Jude discontinued and voluntarily recalled the valve.


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