As the dimensions of dispersed

particles in liquid media reach to the nanometer region, a strong

UV–Vis band appears which is not in the bulk metal spectrum.

Since the structure, size and shape of the metal nanoparticles have

great effects on their optical, electrical and catalytic properties, it

is important to control these parameters. The optical properties of

nanoparticles made of gold and silver have been of interest for

researchers for many decades. These properties of nanoparticles,

which give rise to localized surface plasmon resonance (LSPR)

absorption and scattering, can be used in the development of

analytical methods such as optical sensing, DNA hybridization

and detection. Metal ion detection LSPR excitation results in

wavelength-selective absorption with extremely large molar

extinction coefficients.3 Oscillation of electron cloud on theparticle surface at nano-scale dimensions is associated with the

absorption of particular energy of electromagnetic radiation.

LSPR is a photon driven coherent oscillation of the surface

conduction electrons, which are excited by electromagnetic radiation.

The light interacts with particles much smaller than the

incident wavelength and the electrons in the nanoparticles oscillate

locally around the nanoparticles.4 Especially silver nanoparticles

exhibit excellent LSPR properties. Solutions of colloidal

Ag nanoparticles have distinctive color arising from their tiny

dimensions

the band at 270nm is not the SPR of silver NP its is the SPR of Silver precursor you used.

the SPR of silver nanoparticles (AgNPs) should occurs above 400 nm; i belive you obatained the signature of the silver precursor in the solution, therefore AgNPs were not formed.

Check (calibrate) your spectrometer, the wavelength maybe offset. The solution should looks yellow at low concentration and yellow-green at high concentration.

As the dimensions of dispersed

particles in liquid media reach to the nanometer region, a strong

UV–Vis band appears which is not in the bulk metal spectrum.

Since the structure, size and shape of the metal nanoparticles have

great effects on their optical, electrical and catalytic properties, it

is important to control these parameters. The optical properties of

nanoparticles made of gold and silver have been of interest for

researchers for many decades. These properties of nanoparticles,

which give rise to localized surface plasmon resonance (LSPR)

absorption and scattering, can be used in the development of

analytical methods such as optical sensing, DNA hybridization

and detection. Metal ion detection LSPR excitation results in

wavelength-selective absorption with extremely large molar

extinction coefficients.3 Oscillation of electron cloud on theparticle surface at nano-scale dimensions is associated with the

absorption of particular energy of electromagnetic radiation.

LSPR is a photon driven coherent oscillation of the surface

conduction electrons, which are excited by electromagnetic radiation.

The light interacts with particles much smaller than the

incident wavelength and the electrons in the nanoparticles oscillate

locally around the nanoparticles.4 Especially silver nanoparticles

exhibit excellent LSPR properties. Solutions of colloidal

Ag nanoparticles have distinctive color arising from their tiny

dimensions

i agree with

Javier Reguera idia

Many thanks for the responses, looking at the data again it like we have formed nanoclusters

Nano silver gives an absorption peak at around 480nm. So, I agree with Javier Reguera that it may be a result of formation of nanoclusters which is reason for the peak at 270nm.

For silver nanoparticles absorption band found at 400 nm to 480 nm...

420 nm is the sharp one

The size of the particles and the environment can make a big difference: a dielectric matrix usually decreases the peak energy. In addition to the work quoted by Javier Reguera you might want to check also this paper of ours: JOURNAL OF PHYSICAL CHEMISTRY C Volume: 115 Issue: 49 Pages: 24085-24091 DOI: 10.1021/jp208721. We are currently working on this, let me know if you need more info. Best, Al

the attached word document might be helpful.

As per my experience and studies conducted silver nanoparticles shows absorption at around 420 to 470(480).