Limits...
Detection of formaldehyde in water: a shape-effect on the plasmonic sensing properties of the gold nanoparticles.

Nengsih S, Umar AA, Salleh MM, Oyama M - Sensors (Basel) (2012)

Bottom Line: In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity.However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface.Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microengineering and Nanoelectronic (IMEN), Universiti Kebangsaan Malaysia, UKM Bangi 43600, Selangor, Malaysia. sri_nengsih85@yahoo.com

ABSTRACT
The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity. Spherical nanoparticles (GNS), for example, indicated an increase in the sensitivity when the size was increased from 25 to 35 nm and dramatically decreased when the size was further increased. An m value, the ratio between plasmonic peak shift and refractive index change, as high as 36.5 nm/RIU (refractive index unit) was obtained so far. An expanded sensing mode to FD was obtained when gold nanostructures with nanorods morphology (GNR) were used because of the presence of two plasmonic modes for response probing. However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface. Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects. High performance plasmonic sensors could be obtained if controlled arrays of nanorods can be prepared on the surface.

Show MeSH
Optical absorption spectra of GNR on the substrate surface in water (a) and in the presence of 10% formaldehyde in water (b).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3472829&req=5

f7-sensors-12-10309: Optical absorption spectra of GNR on the substrate surface in water (a) and in the presence of 10% formaldehyde in water (b).

Mentions: Figure 7 shows typical optical absorption spectra of the GNR on the surface in water and in the presence of 10% FD. One point to be noted here is that the obtained spectrum of GNR is not similar to and distorted from that observed in solution (see Figure 3C), in particular at the longitudinal part of the SPR, which exhibits a broader band. This might be due to the effect of intense aggregation amongst the nanorods on the surface, as confirmed by the FESEM image shown in Figure 3. As can be seen from the figure, the absorbance of the GNR independent of the wavelength effectively decreases when the FD is introduced into the surroundings of the GNR, reflecting excellent sensitivity of GNR to the presence of FD in solution. However, as can be seen from the curve, at wavelengths above 950 nm, an absorption tail was observed when the FD was introduced. This could be probably due to an effective interaction of FD and the plasmonic field at this wavelength regime. One point to be noted here is that this response is actually in contrast to those shown by the GNS, in which the absorbance was increased when the medium was changed from water to the FD. Unfortunately, different from those obtained in GNS, in the present system, plasmonic peak shifting at both SPR modes was not obtained. This could be due to the effect of the nature of the optical property of the GNR on the surface, which shows a distorted SPR profile compared to those obtained in solution, a result of GNR-GNR plasmonic coupling in such a close-packed GNR arrangement on the surface. Thus, the shift in the plasmonic absorption peaks due to the change in the refractive index of the medium could not be clearly observed in the spectra. It is true that the current results might not be the typical responses of nanorods to the FD due to the fact the nanorods are not completely localized on the surface. Nevertheless, the present result at least provide promising evidence that the nature of the analyte interaction with nanoparticles is strongly influenced by the shape of nanoparticles. If controlled-arrangement of nanorods on the surface is achieved, enhanced plasmonic sensing will be obtained as a result of the presence of strong localized effects on the SPR of the nanorod. This effort is underway.


Detection of formaldehyde in water: a shape-effect on the plasmonic sensing properties of the gold nanoparticles.

Nengsih S, Umar AA, Salleh MM, Oyama M - Sensors (Basel) (2012)

Optical absorption spectra of GNR on the substrate surface in water (a) and in the presence of 10% formaldehyde in water (b).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472829&req=5

f7-sensors-12-10309: Optical absorption spectra of GNR on the substrate surface in water (a) and in the presence of 10% formaldehyde in water (b).
Mentions: Figure 7 shows typical optical absorption spectra of the GNR on the surface in water and in the presence of 10% FD. One point to be noted here is that the obtained spectrum of GNR is not similar to and distorted from that observed in solution (see Figure 3C), in particular at the longitudinal part of the SPR, which exhibits a broader band. This might be due to the effect of intense aggregation amongst the nanorods on the surface, as confirmed by the FESEM image shown in Figure 3. As can be seen from the figure, the absorbance of the GNR independent of the wavelength effectively decreases when the FD is introduced into the surroundings of the GNR, reflecting excellent sensitivity of GNR to the presence of FD in solution. However, as can be seen from the curve, at wavelengths above 950 nm, an absorption tail was observed when the FD was introduced. This could be probably due to an effective interaction of FD and the plasmonic field at this wavelength regime. One point to be noted here is that this response is actually in contrast to those shown by the GNS, in which the absorbance was increased when the medium was changed from water to the FD. Unfortunately, different from those obtained in GNS, in the present system, plasmonic peak shifting at both SPR modes was not obtained. This could be due to the effect of the nature of the optical property of the GNR on the surface, which shows a distorted SPR profile compared to those obtained in solution, a result of GNR-GNR plasmonic coupling in such a close-packed GNR arrangement on the surface. Thus, the shift in the plasmonic absorption peaks due to the change in the refractive index of the medium could not be clearly observed in the spectra. It is true that the current results might not be the typical responses of nanorods to the FD due to the fact the nanorods are not completely localized on the surface. Nevertheless, the present result at least provide promising evidence that the nature of the analyte interaction with nanoparticles is strongly influenced by the shape of nanoparticles. If controlled-arrangement of nanorods on the surface is achieved, enhanced plasmonic sensing will be obtained as a result of the presence of strong localized effects on the SPR of the nanorod. This effort is underway.

Bottom Line: In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity.However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface.Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microengineering and Nanoelectronic (IMEN), Universiti Kebangsaan Malaysia, UKM Bangi 43600, Selangor, Malaysia. sri_nengsih85@yahoo.com

ABSTRACT
The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity. Spherical nanoparticles (GNS), for example, indicated an increase in the sensitivity when the size was increased from 25 to 35 nm and dramatically decreased when the size was further increased. An m value, the ratio between plasmonic peak shift and refractive index change, as high as 36.5 nm/RIU (refractive index unit) was obtained so far. An expanded sensing mode to FD was obtained when gold nanostructures with nanorods morphology (GNR) were used because of the presence of two plasmonic modes for response probing. However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface. Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects. High performance plasmonic sensors could be obtained if controlled arrays of nanorods can be prepared on the surface.

Show MeSH