Zeolite-sorbate interactions from Raman spectroscopy

Detection of Antigen Protein by Using Fluorescence Cross‐Correlation Spectroscopy and Quantum‐Dot‐Labeled Antibodies

“…This band is attributed to the T‐O‐T bending mode of 4‐membered rings60 largely present in the LTL‐type structure. The splitting of this band (at 470 and 500 cm −1 ) might be attributed to different T‐O‐T angles as has been reported for zeolite Y61 or ZK‐5 62. After 2 h synthesis time (Figure 2A, line c), when zeolite L nanocrystals are not yet detectable by XRD techniques, two additional weak bands at 225 and 314 cm −1 were observed in the Raman spectrum.…”

Stability of Zn(II) Cations in Chabazite Studied by Periodical Density Functional Theory

“…Raman spectroscopy, which also provides vibrational information, often in a complementary manner to infrared spectroscopy, has been studied previously by several authors. ,,, In these works, the T−O−T vibration has been analyzed in the region between 300 and 600 cm -1 . , There are some significant changes in the vibrational spectrum of Na + replaced by Li + in zeolite A. The latter cation tends to distort the zeolite structure because of its strong polarizability and great tendency toward coordination, whereas Na + does not.…”

“…Many experimental studies have been directed to an understanding of the catalytic effect of these cationic species 3,7-15 as well as to determine their location in the zeolite micropores. − Others investigated molecular aspects of the interaction with adsorbate and the cationic position by theoretical means. ,,− Nevertheless, a detailed picture of the cation position inside of zeolites and how this position affects the cation interaction with the probe molecules is still lacking.…”

Raman Spectra of the Unidimensional Aluminophosphate Molecular Sieves AlPO4-11, AlPO4-5, AlPO4-8, and VPI-5

“…Deckman and coworkers have made considerable progress modelling zeolites both as tetrahedrally bonded amorphous solids and as periodic lattices.9-11 This work has given insight into the true nature of experimentally observed Raman shifts with changing Al-O-Si, or Si-O-Si, angle. Obtaining zeolite Raman spectra displaying a good signal-to-noise ratio presents a considerable challenge, largely due to the poor cross section for the inelastic scattering process in aluminosilicates and the pesence of obscuring background fluorescence.1 *'12 *The intensity of this background, which has been related to the zeolite acid strength, can be minimized with careful sample handling; however, each successive postsynthetic treatment leads to an increased background signal.13 *-14 Despite these problems, the increasing maturity of the field of zeolite Raman spectroscopy has been reflected in recent publications detailing the creative use of this method to quantify acidic sites via resonance techniques,13 evaluate zeolite-sorbate inter-actions15' 16 and different silica sources for faujastie synthesis,17 study clathrasil single crystals,18 and monitor the synthesis of zeolites A,19-20 Y,21 and ZSM-5.22'23 With the advantages of Raman as a spectroscopic tool in zeolite chemistry now apparent, it seems appropriate that application of the technique should be extended to other molecular sieve materials. Recently, a spectrum was reported for the aluminophosphate extra-large pore material VPI-524 and we have reported Raman studies of the gallophosphate molecular sieve cloverite.…”