Yazar "Yilmaz, Mehmet" seçeneğine göre listele
Listeleniyor 1 - 4 / 4
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Combining 3-D plasmonic gold nanorod arrays with colloidal nanoparticles as a versatile concept for reliable, sensitive, and selective molecular detection by SERS(ROYAL SOC CHEMISTRY, 2014) Yilmaz, Mehmet; Senlik, Erhan; Biskin, Erhan; Yavuz, Mustafa Selman; Tamer, Ugur; Demirel, GokhanThe detection of molecules at an ultralow level by Surface-Enhanced Raman Spectroscopy (SERS) has recently attracted enormous interest for various applications especially in biological, medical, and environmental fields. Despite the significant progress, SERS systems are still facing challenges for practical applications related to their sensitivity, reliability, and selectivity. To overcome these limitations, in this study, we have proposed a simple yet facile concept by combining 3-D anisotropic gold nanorod arrays with colloidal gold nanoparticles having different shapes for highly reliable, selective, and sensitive detection of some hazardous chemical and biological warfare agents in trace amounts through SERS. The gold nanorod arrays were created on the BK7 glass slides or silicon wafer surfaces via the oblique angle deposition (OAD) technique without using any template material or lithography technique and their surface densities were adjusted by manipulating the deposition angle (a). It is found that gold nanorod arrays fabricated at alpha = 10 degrees exhibited the highest SERS enhancement in the absence of colloidal gold nanoparticles. Synergetic enhancement was obviously observed in SERS signals when combining gold nanorod arrays with colloidal gold nanoparticles having different shapes (i.e., spherical, rod, and cage). Due to their ability to produce localized surface plasmons (LSPs) in transverse and longitudinal directions, utilization of colloidal gold nanorods as a synergetic agent led to an increase in the enhancement factor by about tenfold compared to plain gold nanorod arrays. Moreover, we have tested our approach to detect some chemical and biological toxins namely dipicolinic acid (DIP), methyl parathion (MP), and diethyl phosphoramidate (DP). For all toxins, Raman spectra with high signal-to-noise ratios and reproducibility were successfully obtained over a broad concentration range (5 ppm-10 ppb). Our results suggest that the slightly tangled and closely-packed anisotropic gold nanorod arrays reinforced by the gold nanoparticles may serve as an ideal SERS substrate to detect any analyte in trace amounts.Öğe Light-Driven Unidirectional Liquid Motion on Anisotropic Gold Nanorod Arrays(WILEY-BLACKWELL, 2015) Yilmaz, Mehmet; Kuloglu, Hamit Bugra; Erdogan, Hakan; Cetin, Saime Sebnem; Yavuz, Mustafa Selman; Ince, Gozde Ozaydin; Demirel, Gokhan[Abstract not Available]Öğe Morphological Versatility in the Self-Assembly of Val-Ala and Ala-Val Dipeptides(AMER CHEMICAL SOC, 2015) Erdogan, Hakan; Babur, Esra; Yilmaz, Mehmet; Candas, Elif; Gordesel, Merve; Dede, Yavuz; Oren, Ersin EmreSince the discovery of dipeptide self-assembly, diphenylalanine (Phe-Phe)-based dipeptides have been widely investigated in a variety of fields. Although various supramolecular Phe-Phe-based structures including tubes, vesicles, fibrils, sheets, necklaces, flakes, ribbons, and wires have been demonstrated by manipulating the external physical or chemical conditions applied, studies of the morphological diversity of dipeptides other than Phe-Phe are still required to understand both how these small molecules respond to external conditions such as the type of solvent and how the peptide sequence affects self-assembly and the corresponding molecular structures. In this work, we investigated the self-assembly of valine-alanine (Val-Ala) and alanine-valine (Ala-Val) dipeptides by varying the solvent medium. It was observed that Val-Ala dipeptide molecules may generate unique self-assembly-based morphologies in response to the solvent medium used. Interestingly, when Ala-Val dipeptides were utilized as a peptide source instead of Val-Ala, we observed distinct differences in the final dipeptide structures. We believe that such manipulation may not only provide us with a better understanding of the fundamentals of the dipeptide self-assembly process but also may enable us to generate novel peptide-based materials for various applications.Öğe Physico-chemical and Nutritional Properties of Cornelian Cherry Fruits (Cornus mas L.) Grown in Turkey(ASIAN JOURNAL OF CHEMISTRY, 2009) Kalyoncu, Ismail Hakki; Ersoy, Nilda; Yilmaz, MehmetIn present study, several physical, chemical, pomological and nutritional properties of cornelian cherry fruits (Cornus mas L.) selected from Konya region were determined. The cornelian cherry fruit mean weight, length, width and thickness were found to be 3.130 g, 21.15 mm, 15.5 mm, 15.35 mm, respectively. The seed of fruit mean weight, length, width and thickness were found to be 0.923 g, 14.5 mm. 6.77 mm, 6.2 rum, respectively. In addition to the levels of acidity, pH, total soluble solids, ratio (solids/acidity), texture, colour, tanin, total sugar, invert sugar and ascorbic acid were determined in fruits. Values of the acidity, pH, total soluble solids, ratio (solids/acidity), texture, colour, tanin, total sugar, invert sugar and ascorbic acid were found to be 1.983 mg/100g, 2.617, 15.600 mg/100.g, 7.883, 0.357 kg/cm(2), S60O70M90, 129.503 mg/L, 8.840 mg/100 mL, 7.130 mg/100 mL, 73,007 mg/100 mL, respectively. Studied of nutritional properties K (14300.984 ppm), Ca (1560.095 ppm), Mg (715.231 ppm), P (605.558 ppm) and S (436.754 ppm) were established as major minerals of the cornelian cherry fruits. Others were determined at minor levels. The highest minerals were K and Ca followed by Mg. P and S. On the other hand, some physical properties sphericity and aspect ratio for fruit and seed of cornelian chery fruit were found to be 80.573, 72.727 and 58.830, 46.710% respectively. True density, was found to be 1018.703 kg/m(3).
