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Taking the advantages of surface imprinting, multi-template imprinting and magnetic separation, a novel magnetic multi-template molecularly imprinted polymer (mag-MMIP@MWCNTs) was prepared by using MWCNTs as support material, Fe3O4 as magnetic core, and dimethyl phthalate (DMP), diethyl phthalate (DEP), and dibutyl phthalate (DBP) as template molecules. This composite was characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and the Brunauer-Emmett-Teller (BET) analysis, and was used for the simultaneous adsorption of DMP, DEP, and DBP in aqueous solution. The effects of solution pH, contact time, PAEs initial concentration, temperature, adsorption selectivity, and reusability were investigated and discussed in detail. The results demonstrated that mag-MMIP@MWCNTs exhibited fast kinetics, good magnetic separation, and excellent selectivity for the adsorption of three phthalate esters (PAEs). The adsorption kinetics followed pseudo second-order kinetic model and the adsorption thermodynamics followed Langmuir isothermal model very well, and the maximum adsorption capacities (Qmax) of DMP, DEP, and DBP were obtained as 0.95, 1.38, and 7.09 mg g-1, respectively. The Scatchard analysis revealed that the template-polymer system had a two-site binding behavior. The adsorption thermodynamic studies indicated that the adsorption processes were exothermic and spontaneous, and dominated by physical adsorption relying on hydrogen bond, hydrophobic interaction, and van der Waals force. Mag-MMIP@MWCNTs also showed good reproducibility and reusability for simultaneous adsorption of the three PAEs. The potential application of mag-MMIP@MWCNTs was proved by the removal of DMP, DEP, and DBP spiked in environmental water samples.

Faceted single-crystalline ZnO tubes were synthesized by a simple soft solution method at 65 ° C. These tubes are of several micrometers in length and several hundred nanometers in diameter, with bell-mouths on each end. Structural characterizations using electron spectroscopy revealed that these hexagonal ZnO tubes were along [0 0 0 1] direction and side-enclosed by { 01 1 ¯ 0 } facets. The growth of ZnO in hydrothermal condition and the formation of this unusual bell-mouthed structure were discussed on the basis of the observation of ring-shaped nano-crystallites upon decreasing the time for growth.

We propose a scheme to experimentally investigate cross-talk in closely positioned QD photodetectors. A cross-talk of ∼25.8% at separation of 212 nm is demonstrated in pre-optimized devices.

We propose a color-selective photodetection scheme through integration of Au nanoparticles with CdSe/ZnS quantum dot photodetectors. Preliminary experimental results confirm enhancement of photodetector external quantum efficiency at wavelengths near the plasmonic resonance of Au nanoparticles.

We fabricate Au bowtie nanoantennas by electron beam lithography and study their spectral characteristics using polarization-resolved dark field scattering spectroscopy. A single particle dipole resonance at ∼600 nm and a dimer interaction resonance peak at ∼790 nm are observed. The relative strength of the ∼790 nm resonance increases with decreasing distance between comprising antenna arms while the spectral position stays rather constant, suggesting potential applications when integrated with NEMS actuators. A comparison between our experimental findings and prior work is made and discussed.

Sub-diffraction nanophotonic waveguides are achieved via molecular self-assembly of quantum dots (QDs) and near-field interaction between the QDs. Nanoscale photodetectors with high spatial resolution and sensitivity are also demonstrated by compatible fabrication process.

We present cross-talk calculations for a subdiffraction nanophotonic waveguide that consists of a colloidal quantum dot (QD) array 10 nm in diameter and compare the results with conventional continuous dielectric waveguides, assuming the same 10 nm size as well as a 200 nm cutoff diameter for guided mode. We find that the QD cascade has much lower cross talk than 10 nm dielectric waveguides at an identical separation >30 nm. Moreover, results for 200 nm dielectric waveguides at a 280 nm gap are comparable with those of QD structures spaced 110 nm apart. Hence the proposed QD device is potentially superior to conventional waveguides in achieving lower cross talk in the subdiffraction regime and provides a new route to achieving high-density photonic integrated circuits.

We present loss characterization results for nanophotonic quantum dot waveguides. Loss data measured over 10, 15, and 20 um lengths using 500 nm wide structures show reduced loss compared to other sub-diffraction nanophotonic waveguides.

We report on a waveguide composed of a cascade of gain-enabled quantum dots with subwavelength dimensions. Fabrication is demonstrated through DNA-mediated self-assembly and a two-layer molecular self-assembly process that enables rapid prototyping. The device, which is identified with fluorescence microscopy and tested by optical near field detection, allows optical signal transfer at a well-defined wavelength in flexible routing geometry, such as straight paths and 90 degrees bends. The structure serves as a critical building block for nanophotonic systems with high integration density.

We propose a new approach to experimentally determine the spatial resolution of nanogap quantum dot (QD) photodetectors consist of solution-processed QDs. Cross talk between a pair of closely positioned QD photodetectors was measured. Devices with 200 nm spacing exhibit low crosstalk of 8.4%. A single QD photodetector also shows high sensitivity, with a lowest detectable optical intensity of 95.3 fW/μm2 achieved. The results show the potential of nanogap QD photodetectors for applications in high-density imaging/sensing arrays.

Self-assembled colloidal plasmonic silver nanoparticles monolayers were integrated into solution-processed colloidal quantum dot (QD) photodetectors. We observed plasmon enhancement of photodetector responsivity over a board spectrum range (400–600 nm), with a 1.2–1.6 fold enhancement for a 440-nm-thick QD film device and a 2.4–3.3 fold enhancement for a 100-nm-thick QD device. The enhancement behavior was wavelength dependent with higher enhancement factor at longer wavelengths. The origins of responsivity enhancement were discussed.

Due to its unique optoelectronic properties, the quantum dot (QD) has become a promising material for realizing photonic components and devices with high quantum efficiencies. Quantum dots in colloidal form can have their surfaces modified with various molecules, which enables new fabrication process utilizing molecular self-assembly and can result in new QD photonic device structures in nano-scale. In this review paper, we describe our work on QD waveguides for sub-diffraction limit waveguiding that utilizies near-field optical coupling between QDs, nano-scale QD photodetectors with nanogaps for sensing with high spatial resolution and sensitivity, as well as integration of these two nanophotonic components. The QD waveguide achieved a transmission loss of 3 dB/4 Pm, which is lower than the experimental results from other sub-diffraction limit waveguides that have been reported. It also demonstrated a comparable waveguiding effect through a waveguide with a sharp bend. The QD photodetector showed a sensitivity of 60 pW over a device with a nano- gap of 25 nm for detection. The compatibility between the fabrication processes for these two components with colloidal QDs allows integration of them through self-assembly fabrications.