Recent reports of molecular structures with considerably enhanced two-photon absorption cross-section have generated considerable interest in this phenomenon from both fundamental and applications perspectives. In this letter, we report cooperative enhancement of two-photon absorption in multi-branched structures which may lead to new design criteria for development of highly efficient two-photon materials. The multi-branched structures were synthesized using coupling of two and three two-photon active asymmetric donor-acceptor chromophores linked together by a common amine group. The two-photon cross-sections measured both with nanosecond and femtosecond pulses show that the value for the trimer is more than six times larger than that for the monomer, and not just three times larger as expected from the number density increase.

Three-dimensional graphene architectures with periodic nanopores—reminiscent of zeolite frameworks—are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure. Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures. However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst supports.

This paper presents the use of nanoscale chemistry to synthesize a multilevel, hierarchically built nanoparticle, which we define as a nanoclinic, for targeted diagnostics and therapy. This nanoclinic, produced by multistep chemistry in a nanosize micelle, consists of a thin silica shell encapsulating magnetic (Fe2O3) nanoparticles and fluorescent dyes for enhanced contrast magnetic resonance and optical imaging and magnetic-induced cancer therapy. Furthermore, the surface of these prototype nanoclinics is functionalized with a biotargeting group, luteinizing hormone-releasing hormone (LH−RH). In the work reported here, the LH−RH targets receptor-specific cancer cells for utilization in imaging and investigation of biological effects. The structure and function of these nanoclinics have been characterized using electron and X-ray diffractions, transmission electron microscopy, atomic force and scanning electron microscopy and two-photon laser scanning microscopy. Targeting of the receptor-specific cells has been demonstrated, along with the demonstration of a new mechanism of selective destruction of cancer cells, in a dc magnetic field, using these magnetic nanoclinics.

We have synthesized a series of dendrimers, generations 1 through 3, functionalized with two-photon absorbing (TPA) chromophores at their chain ends. These novel TPA materials were characterized with respect to their one- and two-photon absorption properties.

No abstract

Little is known about the cell-surface molecules that are related to the undifferentiated and pluripotent state of human embryonic stem cells (hESCs). Here, we generated a panel of murine monoclonal antibodies (MAb) against undifferentiated hESCs by a modification of a previously described decoy immunization strategy. H9 hESCs were differentiated in the presence of retinoic acid and used as a decoy immunogen. Twelve Balb/c mice were immunized in the right hind footpads with differentiated H9 cells and in the left hind footpads with undifferentiated H9 cells. After immunization, the left popliteal lymph node cells were collected and were fused with mouse myeloma cells. The fusion resulted in 79 hybridomas secreting MAbs that bound to the undifferentiated H9 cells as shown by flow cytometric analysis. Of these, 70 MAbs bound to the undifferentiated H9 cells, but only weakly or not at all to the differentiated H9 cells. We characterized 37 MAbs (32 IgGs, 5 IgMs) recognizing surface molecules that were down-regulated during embryoid body cell formation. One of the MAbs, L125-C2, was confirmed to immunoprecipitate CD9, previously known as a surface molecule on the undifferentiated hESCs. To investigate the relationship between the MAbs and hESC-specific antibodies, two representative MAbs, viz., L125-C2 and 291-D4, were selected and studied by multi-color flow cytometric analysis. This showed that more than 60% of L125-C2- and 291-D4-positive cells were also positive for the expression of hESC-specific surface molecules such as SSEA3, SSEA4, TRA-1-60, and TRA-1-81, indicating the close relationship between the two MAbs and the hESC-specific surface molecules. Our results suggest that the decoy immunization strategy is an efficient method for isolating a panel of MAbs against undifferentiated hESCs, and that the generated MAbs should be useful for studying the surface molecules on hESCs in the pluripotent and undifferentiated state.

No abstract

No abstract