Carbon nanotubes are attractive new materials. It has been about a decade since carbon nanotubes were discovered. Carbon nanotubes have many outstanding properties and have many practical or potential applications. In this short review we introduce recent advances in carbon nanotubes as potential material for electrochemical sensors. The advantages of carbon nanotubes as sensors are discussed along with future prospects.

Synthesis, characterizations, and photophysical properties of new photoactive dyads and triads containing perylenetetracarboxylic diimide (PIm) and porphyrin (free-base porphyrin (H(2)P) and zinc porphyrin (ZnP)), in which both entities were connected with a short ether bond, were examined with the aim of using these systems for molecular photonics. The porphyrin(P)-PIm systems absorbed strongly across the visible region, which greatly matched the solar spectrum. The geometric and electronic structures of the dyads and triads were probed using density function theory method at the B3LYP/3-21G level. It was revealed that the majority of the highest-occupied molecular orbital was located on the porphyrin entity, while the lowest-unoccupied molecular orbitals were entirely on the PIm entity. The excited-state electron-transfer processes were monitored by both steady-state and time-resolved emission as well as transient-absorption techniques in polar solvent benzonitrile. Upon excitation of the P (H(2)P and ZnP) moieties, efficient fluorescence quenching of the P moiety was observed, suggesting that the main quenching paths involved charge separation from the excited singlet porphyrin ((1)P) to the PIm moiety. Upon excitation of the PIm moiety, fluorescence quenching of the (1)PIm moiety was also observed. The nanosecond transience of spectra in near-IR region revealed the charge separation process from the P moieties to the PIm moiety via their excited singlet states. The lifetimes of the charge-separated states were evaluated to be 7-14 ns, depending on the solvent polarity. Photosensitized electron mediation systems were also revealed in the presence of methyl viologen and sacrificial electron donor.

Intramolecular photoinduced charge-separation and charge-recombination processes of tetrathiafulvalene-(spacer)-naphthalenediimide-(spacer)-tertrathiafulvalenetriads (TTF-(sp)-NIm-(sp)-TTF), which have been designed to change the length and kind of the spacers, have been investigated in various solvents by time-resolved absorption and fluorescence techniques. The fluorescence lifetimes of the NIm moiety considerably decreased compared with that of the NIm molecule, suggesting the photoinduced intramolecular charge-separation via the singlet excited state of the NIm moiety. From the observed short fluorescence lifetimes, the charge-separation rate constants (k CS) and quantum yields (ΦCS) of TTF-(sp)-NIm-(sp)-TTF have been evaluated; the k CS values for the triads with the rigid cyclohexyl spacers are larger than that with long flexible alkyl chain spacers. In the nanosecond transient spectra in PhCN, the absorption bands were observed at 480 and 760 nm, which were attributed to the radical anion of NIm (NIm•-) suggesting the formation of TTF•+-(sp)-NIm•--(sp)-TTF. From the decays of the radical ion-pair, the charge-recombination rate-constants (k CR) were evaluated in the range of 9 × 105 − 3 × 107 s-1. Longer lifetimes of the radical ion-pair were observed for the triads with the cyclohexyl spacer than that of the long flexible spacer. From the temperature dependence of the k CR values, the reorganization energies and coupling constants were experimentally evaluated in PhCN; small coupling constants of the triads with the cyclohexyl spacers than that of the long flexible spacers support the relatively long lifetimes of the charge separated states of the chyclohexyl spacer.

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Poly(methacrylic acid) (PMAA)-coated gelatin nanoparticles encapsulated with fluorescent dye rhodamine B were prepared by the coacervation method with the aim to retard the release of rhodamine B from the gelatin matrix. With sodium sulfate as coacervation reagent for gelatin, a kind of biopolymer with excellent biocompatibility, the formed gelatin nanoparticles were cross-linked by formaldehyde followed by the polymerization of methacrylic acid coating. The fluorescent poly(methacrylic acid) coated gelatin (FPMAAG) nanoparticles had a uniform spherical shape and a size distribution of60±5 nm. Infrared spectral analysis confirmed the formation of PMAA coating on the gelatin nanoparticles. Based on UV-Vis spectra, the loading efficiency of rhodamine B for the FPMAAG nanoparticles was 0.26 μg per mg nanoparticles. The encapsulated rhodamine B could sustain for two weeks. Favorable fluorescence property and fluorescence imaging of cells confirmed that the FPMAAG nanoparticles have promising biochemical, bioanalytical, and biomedical applications.

A glucoamylase-immobilized system based on cross-linked gelatin nanoparticles (CLGNs) was prepared by coacervation method. This system exhibited characteristics of temperature-triggered phase transition, which could be used for enzyme immobilization and release. Their morphology and size distribution were examined by transmission electron microscopy and dynamic light scattering particle size analyzer. Their temperature-triggered glucoamylase immobilization and release features were also further investigated under different temperatures. Results showed that the CLGNs were regularly spherical with diameters of 155±5 nm. The loading efficiencies of glucoamylase immobilized by entrapment and adsorption methods were 59.9% and 24.7%, respectively. The immobilized enzyme was released when the system temperature was above 40°C and performed high activity similar to free enzyme due to the optimum temperature range for glucoamylase. On the other hand, there was no enzyme release that could be found when the system temperature was below 40°C. The efficiency of temperature-triggered release was as high as 99.3% for adsorption method, while the release of enzyme from the entrapment method was not detected. These results indicate that CLGNs are promising matrix for temperature-triggered glucoamylase immobilization and release by adsorption immobilization method.

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We found that core–shell CuInS2/ZnS QDs have obvious temperature dependence and they can be used for accurate intracellular and in vivo temperature sensing after being encapsulated by micelles, which exhibit high intracellular and in vivo thermal sensitivity.