COLLOIDAL GOLD: PRINCIPLES, METHODS, AND APPLICATIONS
BSA LGG FIGURE 1 1 EXAMPLES OF PLASMONIC GNPS AND NANOCOMPOSITES: 16-NM AU NANOSPHERES; GNRS; SIO2/AU NANOSHELLS; GOLD NANOSTARS; PLASMONIC NANOPOWDERS OF GOLD NANOSPHERES, NANORODS, NANOSTARS, AND GOLD/SILVER NANOCAGES; SILVER NANOCUBES; GOLD–SILVER NANOCAGES; AU(CORE)/AG(SHELL) NANOCUBOIDS AND CUBCAGES; NANOCOMPOSITES CONTAINING A GNR CORE AND A MESOPOROUS SILICA SHELL, NANORATTLES CONSISTING OF A HOLLOW MESOPOROUS SILICA SHELL WITH EMBEDDED GOLD NANOSTAR OR AU-AG CAGE; NANOCOMPOSITES CONTAINING A GNR OR NANOCAGE CORE AND A MESOPOROUS SILICA SHELL DOPPED WITH PHOTODYNAMIC (PD) DYE (HERE, HEMATOPORPHYRIN); FLUORESCENT AU-BSA-IGG-PS COM- PLEXES CONSISTING OF AN AU25 CLUSTER STABILIZED BY BSA MOLECULES THAT ARE DOPPED WITH PHOTOSENS PD DYE AND HUMAN ANTISTAPHYLOCOCCAL IMMUNOGLOBULIN, IGG COLLOIDAL GOLD: PRINCIPLES, METHODS, AND APPLICATIONS THE MOST COMMON PHYSICAL APPROACH TO LINEAR NANOPARTICLE PLASMONICS IS BASED ON THE LINEAR LOCAL APPROXIMATION: D R R E R ( , ) ( , ) ( , ), ? ? ? ? = (1 1) WHERE ? IS THE ANGULAR FREQUENCY AND THE ELECTRIC DISPLACEMENT D(R, ?) DEPENDS ON THE ELECTRIC FIELD E(R, ?) AND ON THE DIELECTRIC FUNCTION ?(R, ?) ONLY AT THE SAME POSITION R THEN, THE LINER OPTICAL RESPONSE CAN BE FOUND BY SOLVING THE MAXWELL EQUATIONS WITH APPROPRIATE BOUNDARY CONDITIONS ACTUALLY, IN THE LOCAL APPROXIMATION, THE INDICATING OF POSITION VECTOR IN DIELECTRIC FUNCTIONS ?(R, ?) MAY BE OMITTED AS THE PARTICLE SIZE A IS DECREASED TO THE VALUE COMPARABLE WITH THE ELECTRON MEAN FREE PATH (A~LEFF), DEVIATIONS OF THE PHENOMENOLOGICAL DIELECTRIC FUNCTION ?(?, A) OF THE PAR- TICLE FROM THE BULK VALUES ?(?) = ?(?, A ? LEFF) CAN BE EXPECTED A GENERAL RECIPE FOR THE INCLUSION OF MACROSCOPIC TABULATED DATA AND SIZE EFFECTS TO THE SIZE-DEPENDENT DIELECTRIC FUNCTION CONSISTS IN THE FOLLOWING [45,47] LET ?B(?) BE THE MACROSCOPIC DIELECTRIC FUNC- TION, WHICH CAN BE FOUND IN THE LITERATURE FROM MEASUREMENTS WITH MASSIVE SAMPLES [48] THEN, THE SIZE-DEPENDENT DIELECTRIC FUNCTION OF A PARTICLE IS ? ? ? ? ? ? ( , ) ( ) ( , ), A A B = + ? (1 2) WHERE THE CORRECTION ??(?, A) TAKES INTO ACCOUNT THE CONTRIBUTION OF SIZE-DEPENDENT SCAT- TERING OF ELECTRONS TO THE DRUDE PART OF THE DIELECTRIC FUNCTION DESCRIBED BY THE EXPRESSION ?? ? ? ? ? ? ? ? ? ? ? ( , ) ( ) ( , ) ( ) , A A I B DRUDE P DRUDE P B P = ? = + ? A P I (1 4) (A) (B) (C) K E FIGURE 1 2 SCHEMATIC REPRESENTATION OF THE BULK (A), SURFACE PROPAGATING (B), AND SURFACE LOCAL- IZED (C) PLASMONS THE DASHED LINE SHOWS THE ELECTRON CLOUD DISPLACEMENT (ADAPTED FROM KHLEBTSOV, N G , DYKMAN, L A , J QUANT SPECTROSC RADIAT TRANSFER, 111, 1–35, 2010 WITH PERMISSION ) COLLOIDAL GOLD: PRINCIPLES, METHODS, AND APPLICATIONS