Negative photoconductivity in silver nanocubes prepared by simple photochemical method

Abstract

Silver nanocubes embedded in polyvinyl alcohol matrix have been synthesised by photoirradiation technique. The composite films are characterised by FESEM, XRD, UV-Visible absorption and photoluminescence. These show characteristics of silver nanoparticles with FESEM showing the cubic shape. The photoconductivity study of these films shows decrease in photocurrent with light irradiation. Such negative photoconductivity behaviour may be attributed to dominant scattering of electrons by excited surface plasmon polaritons in nanoscale.Keywords: silver nanoparticles; surface plasmon resonance; photoluminescence; polymer composite; polaritons IntroductionIn metal nanostructures, interesting phenomena [1-3] are exhibited due to surface plasmon polariton (SPP) [4]. Though SPP has capacity to have application potential in both photonics and microelctronics, most of the studies focussed on the optical properties [5][6][7]. Relatively less attention has been paid to the transport properties. Amongst the metals, noble metal (Ag, Au, Pt) nano-sized particles have drawn much attention for their unique electrical and optical properties dependent on their size and shape [8][9][10][11]. In most cases, silver nanoparticles can be obtained by reduction of silver nitrate. Also, to retain their nanosize, one often prepares nanocomposites by embedding the nanoparticles in glass [12], silica [13] or polymers [14][15][16][17][18] such as polyvinyl alcohol (PVA), polyacrilic acid or polymethyl methacrylate, etc. Out of these, PVA is used extensively as host matrix as it is water soluble, optically transparent and gives homogeneity to the silver nano dispersion. The existing methods to reduce silver nitrate in PVA matrix are numerous, to name some simple chemical reduction [19] [23,24]. Among these, the photoreduction method is widely adopted as one can easily obtain very stable nanocomposites by this method. Also, there are reports of obtaining special-shaped nanoparticles [24] other than spherical, with the help of this method. In this article, we explore optical transport (viz. photoconductivity) of cubic silver nano particles embedded in PVA along with their routine characterisation.

Dark Self-Healing-Mediated Negative Photoconductivity of a Lead-Free Cs3Bi2Cl9 Perovskite Single Crystal

“…In some cases, the conductivity upon illumination was reduced below the level of conductivity in the darktermed negative photoconductivity (NPC). This phenomenon is often considered an anomaly; there have been reports on the NPC phenomenon. − Intriguingly, NPC was observed herein for Cs 3 Bi 2 Cl 9 single crystals. A significant current reduction was observed after an illumination time of 15 min, and in the dark, the current recovered slowly to its original value.…”

Observation of Negative Photoconductivity in Lead-Free Cs3Bi2Br9Perovskite Single Crystal

“…In some unusual cases, it was found that conductivity reduces under illumination, below the dark level, which is termed as negative photoconductivity (NPC). Previously, this phenomenon is reported in a wide variety of materials such as Co-doped Si, Se, , InAs, − Ag/Au nanoparticles, , γ-In 2 Se 3 , CNT, − and bidoped ZnSe . The occurrence of NPC in these materials was attributed to various factors such as the introduction of deep acceptor levels, recharged of deep states, light-assisted hot electron trapping in the surface oxide, and moisture adsorption on the surface (acts like scattering center).…”

Filter-free, junctionless structures for color sensing

“…The phenomenon of a decrease in conductivity under illumination with light is called negative photoconductivity. [24][25][26] Kim et al developed plasmonic structures having an anisotropic nanoridge geometry that exhibited broadband photodetection capability. 24 Nevertheless, plasmonic nanoridge structures having widths ranging from 100 to 250 nm would have to be prepared using FIB technology.…”