Counterion effects in cyanine heterojunction photovoltaic devices

We investigated cyanine heterojunction photovoltaic devices using carbocyanine dyes as donors and buckminsterfullerene (C60) as acceptor. In particular, we focused on the influence of cyanine counterions on the photovoltaic device characteristics. It was found that counterions can be displaced in the applied electric field and give rise to important hystereses in the current-voltage characteristics, which are related to charge injection processes at electrode and organic heterointerfaces. Mobile counterions have also a drastic effect on the photocurrent spectrum and are responsible for an important C60 contribution at the organic heterojunction between cyanine and C60. If the counterion is covalently linked to the cyanine dye, the C60 contribution in the blue spectral domain can not be observe

Counterion effects in cyanine heterojunction photovoltaic devices

We investigated cyanine heterojunction photovoltaic devices using carbocyanine dyes as donors and buckminsterfullerene (C60) as acceptor. In particular, we focused on the influence of cyanine counterions on the photovoltaic device characteristics. It was found that counterions can be displaced in the applied electric field and give rise to important hystereses in the current-voltage characteristics, which are related to charge injection processes at electrode and organic heterointerfaces. Mobile counterions have also a drastic effect on the photocurrent spectrum and are responsible for an important C60 contribution at the organic heterojunction between cyanine and C60. If the counterion is covalently linked to the cyanine dye, the C60 contribution in the blue spectral domain can not be observed

Carbohydrate-Based Macromolecular Biomaterials

Carbohydrates are the most abundant and one of the most important biomacromolecules in Nature. Except for energy-related compounds, carbohydrates can be roughly divided into two categories: Carbohydrates as matter and carbohydrates as information. As matter, carbohydrates are abundantly present in the extracellular matrix of animals and cell walls of various plants, bacteria, fungi, etc., serving as scaffolds. Some commonly found polysaccharides are featured as biocompatible materials with controllable rigidity and functionality, forming polymeric biomaterials which are widely used in drug delivery, tissue engineering, etc. As information, carbohydrates are usually referred to the glycans from glycoproteins, glycolipids, and proteoglycans, which bind to proteins or other carbohydrates, thereby meditating the cell-cell and cell-matrix interactions. These glycans could be simplified as synthetic glycopolymers, glycolipids, and glycoproteins, which could be afforded through polymerization, multistep synthesis, or a semisynthetic strategy. The information role of carbohydrates can be demonstrated not only as targeting reagents but also as immune antigens and adjuvants. The latter are also included in this review as they are always in a macromolecular formulation. In this review, we intend to provide a relatively comprehensive summary of carbohydrate-based macromolecular biomaterials since 2010 while emphasizing the fundamental understanding to guide the rational design of biomaterials. Carbohydrate-based macromolecules on the basis of their resources and chemical structures will be discussed, including naturally occurring polysaccharides, naturally derived synthetic polysaccharides, glycopolymers/glycodendrimers, supramolecular glycopolymers, and synthetic glycolipids/glycoproteins. Multiscale structure-function relationships in several major application areas, including delivery systems, tissue engineering, and immunology, will be detailed. We hope this review will provide valuable information for the development of carbohydrate-based macromolecular biomaterials and build a bridge between the carbohydrates as matter and the carbohydrates as information to promote new biomaterial design in the near future. </p

Carbohydrate-Based Macromolecular Biomaterials

Carbohydrates are the most abundant and one of the most important biomacromolecules in Nature. Except for energy-related compounds, carbohydrates can be roughly divided into two categories: Carbohydrates as matter and carbohydrates as information. As matter, carbohydrates are abundantly present in the extracellular matrix of animals and cell walls of various plants, bacteria, fungi, etc., serving as scaffolds. Some commonly found polysaccharides are featured as biocompatible materials with controllable rigidity and functionality, forming polymeric biomaterials which are widely used in drug delivery, tissue engineering, etc. As information, carbohydrates are usually referred to the glycans from glycoproteins, glycolipids, and proteoglycans, which bind to proteins or other carbohydrates, thereby meditating the cell-cell and cell-matrix interactions. These glycans could be simplified as synthetic glycopolymers, glycolipids, and glycoproteins, which could be afforded through polymerization, multistep synthesis, or a semisynthetic strategy. The information role of carbohydrates can be demonstrated not only as targeting reagents but also as immune antigens and adjuvants. The latter are also included in this review as they are always in a macromolecular formulation. In this review, we intend to provide a relatively comprehensive summary of carbohydrate-based macromolecular biomaterials since 2010 while emphasizing the fundamental understanding to guide the rational design of biomaterials. Carbohydrate-based macromolecules on the basis of their resources and chemical structures will be discussed, including naturally occurring polysaccharides, naturally derived synthetic polysaccharides, glycopolymers/glycodendrimers, supramolecular glycopolymers, and synthetic glycolipids/glycoproteins. Multiscale structure-function relationships in several major application areas, including delivery systems, tissue engineering, and immunology, will be detailed. We hope this review will provide valuable information for the development of carbohydrate-based macromolecular biomaterials and build a bridge between the carbohydrates as matter and the carbohydrates as information to promote new biomaterial design in the near future

Dual Molecular Recognition Leading to a Protein–Polymer Conjugate and Further Self-Assembly

Supramolecular conjugation between native protein concanavalin A (ConA) and synthetic polymer PEG (polyethylene glycol) was achieved by dual molecular recognition interactions via a linker, βCD-Man, of which β-cyclodextrin (βCD) and α-mannopyranoside (Man) recognized the adamantane (Ada) end of PEG and lectin ConA orthogonally. Further self-assembly of the resultant supra-conjugates of ConA-PEG was induced by the addition of αCD, which was selectively threaded by PEG chains, leading to nanoparticles in dilute solution or hydrogel at a higher concentration. The moduli of the obtained hydrogel were three magnitudes higher than those of the control sample without ConA, showing the dramatic cross-linking effect of ConA achieved by its rather weak interaction with α-d-mannopyranoside

Photodegradation of cyanine and merocyanine dyes . Dyes and Pigments

Abstract The photodegradation kinetics for some cyanine and merocyanine dyes was studied by UV-visible spectroscopy and the results show that the fading process follows quasi-first-order or zero-order kinetics in acetonitrile. In other experiments, the principal photodegradation products of the dyes were identified with the aid of GC/MS, and it was found that those cyanine dyes holding a positive charge had higher photostability than the corresponding merocyanines. The relationship between photostability and chemical structure was established using PM3 and AM1 MO calculations. Experimental results in this regard suggest that the species associated with the photodegradation of cyanine dyes may be the semioxidized dye free radical cation, Dye þ : . The transient absorption spectra of Dye þ : were determined by nanosecond pump and probe spectroscopy.

Multivalent Host–Guest Hydrogels as Fatigue-Resistant 3D Matrix for Excessive Mechanical Stimulation of Encapsulated Cells

Fatigue resistance of hydrogels is critical to their applications in load-bearing sites of soft tissues that are usually subjected to continuous loadings, such as joint cartilage. However, hydrogels usually swell under physiological conditions and exhibit inevitable fatigue during excessive mechanical loadings. Here we show that hydrogels cross-linked by multivalent host–guest interactions can effectively dissipate a large fraction of the loading energy (>50%) under excessive compressions (over 80% strain, 1000 cycles) despite their high water contents (95%) under physiological conditions. No fatigue is observed in such highly swollen hydrogels during continuous cyclic compressions. We demonstrate that such hydrogels can be used as 3D cell carriers for excessive mechanical stimulation of the encapsulated stem cells, making them promising soft biomaterials for tissue engineering