Yizhuang Xu

Orthogonal Sample Design Scheme for Two-Dimensional Synchronous Spectroscopy and Its Application in Probing Intermolecular Interactions

This paper introduces a new approach to probing intermolecular interactions based on a framework of two-dimensional (2D) synchronous spectroscopy. Mathematical analysis performed on 2D synchronous spectra using variable concentration as an external perturbation shows that the cross-peaks are composed of two parts. The first part reflects intermolecular interactions that manifest in the form of deviation from the Beer–Lambert law. The second part is related simply to the concentration variations of the solutes and is responsible for the generation of interfering cross-peaks not related to the intermolecular interactions in the system. It is the second part that prevents the reliable identification of intermolecular interactions. We propose a way of selecting the concentrations of solutes so that the resultant dynamic concentration vectors of different solutes become orthogonal to one another. Therefore, the contribution of the second part to the cross-peaks can be effectively removed by the dot product of orthogonal vectors. Our new approach has been tested on a simulated chemical system and a real chemical system. The results demonstrate that interfering cross-peaks can be successfully removed from a 2D synchronous spectrum so that the cross-peaks can be used as a reliable tool to characterize or probe intermolecular interactions.

Asynchronous Orthogonal Sample Design Scheme for Two-Dimensional Correlation Spectroscopy (2D-COS) and Its Application in Probing Intermolecular Interactions from Overlapping Infrared (IR) Bands

This paper introduces a new approach to analysis of spectra called asynchronous orthogonal sample design (AOSD). Specifically designed concentration series are selected according to mathematical analysis of orthogonal vectors. Based on the AOSD approach, the interfering portion of the spectra arising strictly from the concentration effect can be completely removed from the asynchronous spectra. Thus, two-dimensional (2D) asynchronous spectra can be used as an effective tool to characterize intermolecular interactions that lead to apparent deviations from the Beer–Lambert law, even if the characteristic peaks of two compounds are substantially overlapped. A model solution with two solutes is used to investigate the behavior of the 2D asynchronous spectra under different extents of overlap of the characteristic peaks. Simulation results demonstrate that the resulting spectral patterns can reflect subtle spectral variations in bandwidths, peak positions, and absorptivities brought about by intermolecular interaction, which are barely visualized in the conventional one-dimensional (1D) spectra. Intermolecular interactions between butanone and dimethyl formamide (DMF) in CCl4 solutions were investigated using the proposed AOSD approach to prove the applicability of the AOSD method in real chemical systems.

Double Orthogonal Sample Design Scheme and Corresponding Basic Patterns in Two-Dimensional Correlation Spectra for Probing Subtle Spectral Variations Caused by Intermolecular Interactions

This paper introduces a new approach named double orthogonal sample design scheme (DOSD) to probe intermolecular interactions based on a framework of two-dimensional (2D) correlated spectroscopy. In this approach, specifically designed concentration series are selected according to the mathematical analysis on orthogonal vectors to generate useful 2D correlated spectra. As a result, the interfering portion can be completely removed from both synchronous and asynchronous spectra, and complementary information concerning intermolecular interactions can be obtained from the set of 2D spectra. A model system, where intermolecular interactions occur between two solutes in a solution, is used to investigate the behavior of 2D correlated spectra generated by using the DOSD approach. Simulation results demonstrate that the resultant spectral patterns can reflect subtle spectral variation in bandwidths, peak positions, and absorptivities brought about by intermolecular interaction, which are hardly visualized in conventional 1D spectra because of the severe band-overlapping problem. The ability to reveal a subtle variation in a characteristic peak in detail by using the DOSD approach provides a new opportunity to understand the nature of intermolecular interactions from a molecular structural point of view. Intermolecular interactions between iodine and benzene in CCl(4) solutions were investigated by using the proposed DOSD approach to prove the applicability of the DOSD method in real chemical systems.

Double asynchronous orthogonal sample design scheme for probing intermolecular interactions.

This paper introduces a new approach called double asynchronous orthogonal sample design (DAOSD) to probe intermolecular interactions. A specifically designed concentration series is selected according to the mathematical analysis to generate useful 2D correlated spectra. As a result, the interfering portions are completely removed and a pair of complementary sub-2D asynchronous spectra can be obtained. A computer simulation is applied on a model system with two solutes to study the spectral behavior of cross peaks in 2D asynchronous spectra generated by using the DAOSD approach. Variations on different spectral parameters, such as peak position, bandwidth, and absorptivity, caused by intermolecular interactions can be estimated by the characteristic spectral patterns of cross peaks in the pair of complementary sub-2D asynchronous spectra. Intermolecular interactions between benzene and iodine in CCl(4) solutions were investigated using the DAOSD approach to prove the applicability of the DAOSD method in real chemical system.

Detection of lung cancer tissue by attenuated total reflection–Fourier transform infrared spectroscopy—a pilot study of 60 samples

BACKGROUND Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy could serve as a diagnostic tool for detecting and discriminating different diseases. The aim of this preliminary study was to distinguish malignant and nonmalignant lung tissues with ATR-FTIR spectroscopy. METHODS Sixty lung tissue samples were obtained from 30 patients who underwent pulmonary lobectomy. Samples were examined with ATR-FTIR spectroscopy before histologic diagnosis. Peak positions, intensities, and full width at half maximum of each absorbent band were measured, and the relative intensity ratios were calculated. Canonical discriminant analysis was performed to discriminate malignant and nonmalignant groups. RESULTS Twenty-two parameters were significantly different between malignant and nonmalignant groups. Peak intensity at 1546/cm, intensity ratio at 1120/cm, and full width at half maximum at 1303 and 1240/cm were selected as independent factors to form discriminant functions. The sensitivity and specificity of the discriminants were all 96.7%. CONCLUSIONS ATR-FTIR spectroscopy is a promising method for the detection of malignant lung tissue and could be proved useful in lung tumor surgery.

Intraoperative Detection of Thyroid Carcinoma by Fourier Transform Infrared Spectrometry

BACKGROUND Fourier transform infrared (FTIR) spectroscopy is a powerful tool for distinguishing cancerous tissue from normal one. Our aim in this study was to establish tissue discriminant analysis for thyroid malignancy and benign samples intraoperatively using FTIR spectroscopy. METHODS Seventeen papillary thyroid cancer and 43 nodular goiter tissues were obtained and underwent FTIR spectroscopy scanning intraoperatively. Nine peak positions were identified and assigned. Peak position values and wave intensity ratios were measured in every single spectrum. Data of malignant and benign groups were compared and equations of canonical discriminant analysis were established. RESULTS Peak positions of P1640, P1240, P1550, and peak intensity ratios of I3375/I1460, I1640/I1460, I1400/I1460, I1550/I1080, I1080/I1460, and I1640/I1550 of thyroid papillary carcinoma group are significantly different from nodular goiter group. The sensitivity, specificity, and accuracy rate of the discriminants are 83.3%, 95.2%, and 91.67%, respectively. CONCLUSION FTIR spectroscopy technique in combination with canonical discriminant analysis method can achieve fast and accurate discrimination for malignant and benign thyroid nodules during operation.

Evaluation of FTIR spectroscopy as diagnostic tool for colorectal cancer using spectral analysis

The aim of this study is to confirm FTIR spectroscopy as a diagnostic tool for colorectal cancer. 180 freshly removed colorectal samples were collected from 90 patients for spectrum analysis. The ratios of spectral intensity and relative intensity (/I1460) were calculated. Principal component analysis (PCA) and Fishers discriminant analysis (FDA) were applied to distinguish the malignant from normal. The FTIR parameters of colorectal cancer and normal tissues were distinguished due to the contents or configurations of nucleic acids, proteins, lipids and carbohydrates. Related to nitrogen containing, water, protein and nucleic acid were increased significantly in the malignant group. Six parameters were selected as independent factors to perform discriminant functions. The sensitivity for FTIR in diagnosing colorectal cancer was 96.6% by discriminant analysis. Our study demonstrates that FTIR can be a useful technique for detection of colorectal cancer and may be applied in clinical colorectal cancer diagnosis.

Low-frequency vibrational modes of dl-homocysteic acid and related compounds

In this paper several polycrystalline molecules with sulfonate groups and some of their metal complexes, including DL-homocysteic acid (DLH) and its Sr- and Cu-complexes, pyridine-3-sulphonic acid and its Co- and Ni-complexes, sulfanilic acid and L-cysteic acid were investigated using THz time-domain methods at room temperature. The results of THz absorption spectra show that the molecules have characteristic bands in the region of 0.2-2.7 THz (6-90 cm(-1)). THz technique can be used to distinguish different molecules with sulfonate groups and to determine the bonding of metal ions and the changes of hydrogen bond networks. In the THz region DLH has three bands: 1.61, 1.93 and 2.02 THz; and 0.85, 1.23 and 1.73 THz for Sr-DLH complex, 1.94 THz for Cu-DLH complex, respectively. The absorption bands of pyridine-3-sulphonic acid are located at 0.81, 1.66 and 2.34 THz; the bands at 0.96, 1.70 and 2.38 THz for its Co-complex, 0.76, 1.26 and 1.87 THz for its Ni-complex. Sulphanilic acid has three bands: 0.97, 1.46 and 2.05 THz; and the absorption bands of l-cysteic acid are at 0.82, 1.62, 1.87 and 2.07 THz, respectively. The THz absorption spectra after complexation are different from the ligands, which indicate the bonding of metal ions and the changes of hydrogen bond networks. M-O and other vibrations appear in the FIR region for those metal-ligand complexes. The bands in the THz region were assigned to the rocking, torsion, rotation, wagging and other modes of different groups in the molecules. Preliminary assignments of the bands were carried out using Gaussian program calculation.

Two-dimensional asynchronous spectrum with auxiliary cross peaks in probing intermolecular interactions

A new approach called “asynchronous spectrum with auxiliary peaks (ASAP)” is proposed for generating a 2D asynchronous spectrum to investigate the intermolecular interaction between two solutes (P and Q) dissolved in the same solution. In the ASAP approach, a virtual substance S with an isolated peak assumed to be at νS is introduced, while the characteristic peaks of P and Q are actually observed at νP and νQ. The concentrations series of P, Q and S are specifically designed so that a spectral portion that has nothing to do with the intermolecular interaction between P and Q is completely removed from the 2D asynchronous spectrum. Auxiliary cross peaks around (νP, νS) and (νQ, νS) can be used to reveal spectral variation caused by intermolecular interaction, which cannot be observed on conventional cross peaks appearing around the spectral coordinates (νP, νP), (νP, νQ), (νQ, νP), (νQ, νQ). For example, variation of the absorptivity of P caused by an intermolecular interaction between P and Q can be probed from the auxiliary cross peaks around (νP, νS) when Q does not even have any characteristic peak in the observed spectral range.

Spectroscopic and TEM studies on poly vinyl carbazole/terbium complex and fabrication of organic electroluminescent device

Abstract Terbium acetyl salicylate complex containing 1,10-phenanthroline was synthesized. Element analysis showed that the composition of the complex was Tb(C 9 O 4 H 7 ) 3 (C 12 N 2 H 8 ). A single layer electroluminescent device using polyvinyl carbazole doped with the terbium complex as an emitting layer was fabricated. The device showed bright green EL emission. The dispersion of the terbium complex in PVK matrix was investigated using transmission electron microscopy.