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Smart and Reversible Surface Plasmon Resonance Responses to Various Atmospheres for Silver Nanoparticles Loaded in Mesoporous SiO2

“…AHS yields an emission centered at 350 nm and another emission centered at 420 nm, shown in curve a, whereas both the HS sample and air-annealed mesoporous SiO 2 have no PL emission in the wavelength range, presented in curves b and c. The PL spectra of the AHS sample herein are not similar to those of other kinds of isolated Ag oxidation products reported elsewhere . However, it had been reported by other researchers that there exists fluorescence of Ag + due to the 4d 9 5s → 4d 10 transition, strictly forbidden for the free ion but partially allowed in crystals or glasses. , Thus, here it can be deduced that Ag + is produced in air at high temperature for Ag/mesoporous SiO 2 and that the dangling bonds of mesoporous SiO 2 would provide suitable local conditions for the transition between energy levels in Ag + that is originally forbidden. Thus, the emission band centered at 350 nm is attributed to the 4d 9 5s → 4d 10 partially allowed transition in Ag + ions diluted in the SiO 2 matrix and the other emission centered at 420 nm is attributed to the Ag + −Ag + pair, − which can be stabilized by the local electric field due to the dangling bonds.…”

“…8 However, it had been reported by other researchers that there exists fluorescence of Ag + due to the 4d 9 5s f 4d 10 transition, strictly forbidden for the free ion but partially allowed in crystals or glasses. 38,39 Thus, here it can be deduced that Ag + is produced in air at high temperature for Ag/mesoporous SiO 2 and that the dangling bonds of mesoporous SiO 2 would provide suitable local conditions for the transition between energy levels in Ag + that is originally forbidden. Thus, the emission band centered at 350 nm is attributed to the 4d 9 5s f 4d 10 partially allowed transition in Ag + ions diluted in the SiO 2 matrix and the other emission centered at 420 nm is attributed to the Ag + -Ag + pair, [39][40][41] which can be stabilized by the local electric field due to the dangling bonds.…”

“…38,39 Thus, here it can be deduced that Ag + is produced in air at high temperature for Ag/mesoporous SiO 2 and that the dangling bonds of mesoporous SiO 2 would provide suitable local conditions for the transition between energy levels in Ag + that is originally forbidden. Thus, the emission band centered at 350 nm is attributed to the 4d 9 5s f 4d 10 partially allowed transition in Ag + ions diluted in the SiO 2 matrix and the other emission centered at 420 nm is attributed to the Ag + -Ag + pair, [39][40][41] which can be stabilized by the local electric field due to the dangling bonds. Heat treatment of the AHS sample in H 2 again led to the reduction of Ag + ions to metallic Ag nanoparticles, resulting in the disappearance of the PL emission.…”

Substrate dependent surface plasmon resonance evolution of Ag nanoparticles treated in atmospheres

“…In fact, previous research on photoluminescence spectra [23,24] also suggested that there are Ag + ions diluted in the SiO 2 matrix for the sol-gel SiO 2 containing silver after air annealing. Hence the initial air-heat treatment led to the disappearance of the SPR absorption (see curve (b) of figure 1).…”

Influência dos precursores de prata no crescimento de nanopartículas metálicas em vidros óxidos de metais pesados

“…Assim, devemos considerar que a prata deve estar na forma de clusters, contendo somente alguns átomos metálicos e com dimensões muito reduzidas, uma vez que não foi possível observar a presença de nanopartículas por microscopia eletrônica nestas amostras. A confirmação da formação de 18 Mitrikas e col. também associaram o sinal de RPE observado em g = 2,0, assim como as curvas de recuperação do eco de spin eletrônico, em matrizes de SiO 2 dopadas com AgNO 3 com a presença de nanopartículas de prata. 19 As pequenas diferenças observadas nos valores de g com relação ao valor da prata metálica (g = 1,9827) têm sido atribuídas a efeitos quânticos nos agregados de prata.…”