A DFTB study on the electronic response of encapsulated DNA nucleobases onto chiral CNTs as a sequencer.

Sequencing the DNA nucleobases is essential in the diagnosis and treatment of many diseases related to human genes. In this article, the encapsulation of DNA nucleobases with some of the important synthesized chiral (7, 6), (8, 6), and (10, 8) carbon nanotubes were investigated. The structures were modeled by applying density functional theory based on tight binding method (DFTB) by considering semi-empirical basis sets. Encapsulating DNA nucleobases on the inside of CNTs caused changes in the electronic properties of the selected chiral CNTs. The results confirmed that van der Waals (vdW) interactions, π-orbitals interactions, non-bonded electron pairs, and the presence of high electronegative atoms are the key factors for these changes. The result of electronic parameters showed that among the CNTs, CNT (8, 6) is a suitable choice in sequencing guanine (G) and cytosine (C) DNA nucleobases. However, they are not able to sequence adenine (A) and thymine (T). According to the band gap energy engineering approach and absorption energy, the presence of G and C DNA nucleobases decreased the band gap energy of CNTs. Hence selected CNTs suggested as biosensor substrates for sequencing G and C DNA nucleobases.

Ab Initio investigation for DNA nucleotide bases sequencing using chiral carbon nanobelts and nanotubes.

Understanding the interaction mechanism between DNA nucleotide bases and carbon nanomaterials is an important issue in the field of identifying nucleotide molecules sequencing. In this article, the adsorption behavior of DNA nucleotide bases on the external surface of chiral carbon nanobelts (CNBs) (6, 5), (7, 6) and (8, 6), was comprehensively investigated from electronic and optical perspectives. As a result, it was determined that the DNA nucleotide bases have optical absorption in the ultraviolet region. When bases are adsorbed on the surface of CNBs, the optical absorption peak of the new complex structure shifted to the visible region. The study of the optical properties of selected CNBs showed that CNB (6,5) performs better in detecting Cytosine and the red shift in the absorption spectrum of complex structure is noticeable. Also, the effect of infinite length for chiral CNTs in DNA nucleotide base sequencing was investigated using DFTB approach. Our investigations based on electronic properties showed that CNTs have better performance than CNBs in DNA nucleotide base sequencing.

Carbon nanotubes and nanobelts as potential materials for biosensor.

We investigate the electronic response of single-walled carbon nanotubes (SWCNTs) and a carbon nanobelt (CNB) to N-linked and O-linked SARS-CoV-2 spike glycoproteins, using ab initio quantum mechanical approach. The CNTs are selected from three zigzag, armchair, and chiral groups. We examine the effect of carbon nanotube (CNT) chirality on the interaction between CNTs and glycoproteins. Results indicate that the chiral semiconductor CNTs clearly response to the presence of the glycoproteins by changing the electronic band gaps and electron density of states (DOS). Since the changes in the CNTs band gaps in the presence of N-linked are about two times larger than the changes in the presence of the O-linked glycoprotein, chiral CNT may distinguish different types of the glycoproteins. The same results are obtained from CNBs. Thereby, we predict CNBs and chiral CNTs have suitable potential in sequential analysis of N- and O-linked glycosylation of the spike protein.

Deposition of Nanostructured CdS Thin Films by Thermal Evaporation Method: Effect of Substrate Temperature.

Nanocrystalline CdS thin films were grown on glass substrates by a thermal evaporation method in a vacuum of about 2 × 10-5 Torr at substrate temperatures ranging between 25 °C and 250 °C. The physical properties of the layers were analyzed by transmittance spectra, XRD, SEM, and four-point probe measurements, and exhibited strong dependence on substrate temperature. The XRD patterns of the films indicated the presence of single-phase hexagonal CdS with (002) orientation. The structural parameters of CdS thin films (namely crystallite size, number of grains per unit area, dislocation density and the strain of the deposited films) were also calculated. The resistivity of the as-deposited films were found to vary in the range 3.11-2.2 × 104 Ω·cm, depending on the substrate temperature. The low resistivity with reasonable transmittance suggest that this is a reliable way to fine-tune the functional properties of CdS films according to the specific application.

Effect of blocking layer to boost photoconversion efficiency in ZnO dye-sensitized solar cells.

The effect of a ZnO compact blocking layer (BL) in dye-sensitized solar cells (DSSCs) based on ZnO photoanodes is investigated. BL is generated through spray deposition onto fluorine-doped tin oxide (FTO) conducting glass before the deposition of a ZnO active layer. The functional properties of dye-sensitized solar cells (DSSCs) are then investigated as a function of the thickness of the BL for two different kinds of ZnO active layer, i.e., hierarchically self-assembled nanoparticles and microcubes composed of closely packed ZnO sheets. Presence of BL leads to the improvement of photoconversion efficiency (PCE), by physically insulating the electrolyte and the FTO. This effect increases at increasing BL thickness up to around 800 nm, while thicker BL results in reduced cell performance. Remarkable increase in Jsc is recorded, which doubles as compared to cells without blocking layer, leading to PCE as high as 5.6% in the best cell under one sun irradiation (AM 1.5 G, 100 mW cm(-2)). Electrochemical impedance spectroscopy (EIS) elucidates the mechanism boosting the functional features of the cells with BL, which relies with enhanced chemical capacitance together with an almost unchanged recombination resistance, which are reflected in an increased electron lifetime. The results foresee a straightforward way to significantly improve the performance of ZnO-based DSSCs.