Limits...
Monitoring of degradation of porous silicon photonic crystals using digital photography.

Ariza-Avidad M, Nieto A, Salinas-Castillo A, Capitan-Vallvey LF, Miskelly GM, Sailor MJ - Nanoscale Res Lett (2014)

Bottom Line: As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green.A monotonic relationship was observed between the wavelength of the rugate reflectance peak and an H parameter value calculated from the average red-green-blue (RGB) values of each image by first independently normalizing each channel (R, G, and B) using their maximum and minimum value over the time course of the degradation process.Spectrophotometric measurements and digital image analysis using this H parameter gave consistent relative stabilities of the samples as fpSi > pSi-ch.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA ; Department of Analytical Chemistry, University of Granada, Faculty of Sciences, Avda. Fuentenueva s/n, Granada E-18071, Spain.

ABSTRACT
We report the monitoring of porous silicon (pSi) degradation in aqueous solutions using a consumer-grade digital camera. To facilitate optical monitoring, the pSi samples were prepared as one-dimensional photonic crystals (rugate filters) by electrochemical etching of highly doped p-type Si wafers using a periodic etch waveform. Two pSi formulations, representing chemistries relevant for self-reporting drug delivery applications, were tested: freshly etched pSi (fpSi) and fpSi coated with the biodegradable polymer chitosan (pSi-ch). Accelerated degradation of the samples in an ethanol-containing pH 10 aqueous basic buffer was monitored in situ by digital imaging with a consumer-grade digital camera with simultaneous optical reflectance spectrophotometric point measurements. As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green. While the H coordinate in the hue, saturation, and value (HSV) color space calculated using the as-acquired photographs was a good monitor of degradation at short times (t < 100 min), it was not a useful monitor of sample degradation at longer times since it was influenced by reflections of the broad spectral output of the lamp as well as from the narrow rugate reflectance band. A monotonic relationship was observed between the wavelength of the rugate reflectance peak and an H parameter value calculated from the average red-green-blue (RGB) values of each image by first independently normalizing each channel (R, G, and B) using their maximum and minimum value over the time course of the degradation process. Spectrophotometric measurements and digital image analysis using this H parameter gave consistent relative stabilities of the samples as fpSi > pSi-ch.

No MeSH data available.


Images showing color change of pSi sample during degradation and mask used to select pixels for image analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4155483&req=5

Figure 2: Images showing color change of pSi sample during degradation and mask used to select pixels for image analysis.

Mentions: The jpg images were pre-processed using Photoshop CS5 (Adobe Systems, San Jose, CA, USA). First, a color curve balance correction for each image was made selecting as a reference point a portion of the silicon wafer that was not in contact with the buffer solution. Next, the portion of each image containing the pixels corresponding to the degrading porous silicon sample (ca. 1.2 × 105 pixels) was defined using a mask, Figure 2. The average RGB values for these pixels were determined for each image. The H coordinate, or hue, [9] of the HSV (hue, saturation, and value) color space, was used to monitor the porous Si degradation since it represents the dominant color in one single parameter. The RGB values of the selected pixels in each image were processed with a set of scripts and functions developed in Matlab r2010b (The MathWorks Inc, Natick, MA, USA) to determine the H coordinate, which is defined as in Equation 1.


Monitoring of degradation of porous silicon photonic crystals using digital photography.

Ariza-Avidad M, Nieto A, Salinas-Castillo A, Capitan-Vallvey LF, Miskelly GM, Sailor MJ - Nanoscale Res Lett (2014)

Images showing color change of pSi sample during degradation and mask used to select pixels for image analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4155483&req=5

Figure 2: Images showing color change of pSi sample during degradation and mask used to select pixels for image analysis.
Mentions: The jpg images were pre-processed using Photoshop CS5 (Adobe Systems, San Jose, CA, USA). First, a color curve balance correction for each image was made selecting as a reference point a portion of the silicon wafer that was not in contact with the buffer solution. Next, the portion of each image containing the pixels corresponding to the degrading porous silicon sample (ca. 1.2 × 105 pixels) was defined using a mask, Figure 2. The average RGB values for these pixels were determined for each image. The H coordinate, or hue, [9] of the HSV (hue, saturation, and value) color space, was used to monitor the porous Si degradation since it represents the dominant color in one single parameter. The RGB values of the selected pixels in each image were processed with a set of scripts and functions developed in Matlab r2010b (The MathWorks Inc, Natick, MA, USA) to determine the H coordinate, which is defined as in Equation 1.

Bottom Line: As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green.A monotonic relationship was observed between the wavelength of the rugate reflectance peak and an H parameter value calculated from the average red-green-blue (RGB) values of each image by first independently normalizing each channel (R, G, and B) using their maximum and minimum value over the time course of the degradation process.Spectrophotometric measurements and digital image analysis using this H parameter gave consistent relative stabilities of the samples as fpSi > pSi-ch.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA ; Department of Analytical Chemistry, University of Granada, Faculty of Sciences, Avda. Fuentenueva s/n, Granada E-18071, Spain.

ABSTRACT
We report the monitoring of porous silicon (pSi) degradation in aqueous solutions using a consumer-grade digital camera. To facilitate optical monitoring, the pSi samples were prepared as one-dimensional photonic crystals (rugate filters) by electrochemical etching of highly doped p-type Si wafers using a periodic etch waveform. Two pSi formulations, representing chemistries relevant for self-reporting drug delivery applications, were tested: freshly etched pSi (fpSi) and fpSi coated with the biodegradable polymer chitosan (pSi-ch). Accelerated degradation of the samples in an ethanol-containing pH 10 aqueous basic buffer was monitored in situ by digital imaging with a consumer-grade digital camera with simultaneous optical reflectance spectrophotometric point measurements. As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green. While the H coordinate in the hue, saturation, and value (HSV) color space calculated using the as-acquired photographs was a good monitor of degradation at short times (t < 100 min), it was not a useful monitor of sample degradation at longer times since it was influenced by reflections of the broad spectral output of the lamp as well as from the narrow rugate reflectance band. A monotonic relationship was observed between the wavelength of the rugate reflectance peak and an H parameter value calculated from the average red-green-blue (RGB) values of each image by first independently normalizing each channel (R, G, and B) using their maximum and minimum value over the time course of the degradation process. Spectrophotometric measurements and digital image analysis using this H parameter gave consistent relative stabilities of the samples as fpSi > pSi-ch.

No MeSH data available.