Energy/Charge Transfer Modulation with Spacer Ligands for Highly Emissive Quantum Dot-Polymer Blend

A blend of perovskite quantum dots (QDs) and a hole transport layer (HTL) is a feasible candidate to solve the long-standing issues in light-emitting diodes (LEDs) such as charge injection, energy state matching, and defect passivation. However, QD:HTL blend structures for QD-based LEDs suffer from fast charge and energy transfers due to an inhomogeneous distribution of QDs and the HTL matrix. Here we report new cross-linkable spacer ligands between QDs and TFB that result in a highly emissive QD:TFB-blended LED device. We synthesize three representative spacer ligands to control the charge and energy transfers between QDs and the HTL. The first spacer ligand is used for controlling the molecular distance between QDs and TFB, and the second spacer ligand is designed to investigate how molecular interaction between QDs and the spacer ligand affects the optical property of the QD:TFB blend. Subsequently, the best spacer ligand, a 10-((2-benzoylbenzoyl)oxy)decanoic acid, is designed to anchor TFB (via a benzophenone group) and simultaneously bond to QDs (with a carboxylic acid functional group). The carboxylic acid group strongly interacts with QDs, dramatically improving the cross-linking rate between QDs and TFB. Due to the direct interaction between QDs and TFB, hole carriers can be effectively injected to perovskite QDs through the conductive backbone of TFB, resulting in the highest luminance values of 10917 cd/m² at 7.4 V due to carrier injection balance. This is at least 10 times better LED performance compared with a pristine QD device.

Nitrogen-doped carbon quantum dots conjugated isoreticular metal-organic framework-3 particles based luminescent probe for selective sensing of trinitrotoluene explosive

Amine group-containing isoreticular metal-organic framework (IRMOF-3) particles are utilized for the first time as a trinitrotoluene (TNT) sensing material. IRMOF-3 particles are synthesized using zinc nitrate as a metal precursor and 2-amino-1,4-benzenedicarboxylic acid as a linker. The nitrogen-doped carbon quantum dots (NCQDs) are synthesized from citric acid and ethylenediamine as carbon and nitrogen precursor, respectively. The NCQDs are conjugated with IRMOF-3 particles as IRMOF-3/NCQDs. The TEM micrograph revealed the average size of IRMOF-3 particles to be 363.66 nm. The photoluminescence emission intensity of IRMOF-3 particles at λ_em 430 nm is highly increased in the presence of NCQDs (λ_ex 330 nm). Both the as-synthesized IRMOF-3 and IRMOF-3/NCQD particles are explored for TNT detection to compare the effect of NCQDs on the IRMOF-3 particle surface. Lower limit of detection (7.5 × 10^-8 M) and higher Stern-Volmer constant (4.46 × 10⁶ M^-1) are achieved by IRMOF-3/NCQD particles. The association constant also increased from 5.3 × 10⁴ to 2.78 × 10⁶ M^-1 after the conjugation of IRMOF-3 particles with NCQDs. Moreover, enhanced selectivity for TNT over trinitrophenol is achieved using the IRMOF-3/NCQD particles. Graphical Abstract.

Photoluminescence Quenching and Enhanced Optical Conductivity of P3HT-Derived Ho(3+)-Doped ZnO Nanostructures

In this article, we demonstrate the surface effect and optoelectronic properties of holmium (Ho(3+))-doped ZnO in P3HT polymer nanocomposite. We incorporated ZnO:Ho(3+) (0.5 mol% Ho) nanostructures in the pristine P3HT-conjugated polymer and systematically studied the effect of the nanostructures on the optical characteristics. Detailed UV-Vis spectroscopy analysis revealed enhanced absorption coefficient and optical conductivity in the P3HT-ZnO:Ho(3+) film as compared to the pristine P3HT. Moreover, the obtained photoluminescence (PL) results established the improvement of exciton dissociation as a result of ZnO:Ho(3+) nanostructures inclusion. The occurrence of PL quenching is the result of enhanced charge transfer due to ZnO:Ho(3+) nanostructures in the polymer, whereas energy transfer from ZnO:Ho(3+) to P3HT was verified. Overall, the current investigation revealed a systematic tailoring of the optoelectronic properties of pristine P3HT after inclusion of ZnO:Ho(3+) nanostructures, thus opening brilliant perspectives for applications in various optoelectronic devices.

Methods to Characterize the Oligonucleotide Functionalization of Quantum Dots

Currently, DNA nanotechnology offers the most programmable, scalable, and accurate route for the self-assembly of matter with nanometer precision into 1, 2, or 3D structures. One example is DNA origami that is well suited to serve as a molecularly defined "breadboard", and thus, to organize various nanomaterials such as nanoparticles into hybrid systems. Since the controlled assembly of quantum dots (QDs) is of high interest in the field of photonics and other optoelectronic applications, a more detailed view on the functionalization of QDs with oligonucleotides shall be achieved. In this work, four different methods are presented to characterize the functionalization of thiol-capped cadmium telluride QDs with oligonucleotides and for the precise quantification of the number of oligonucleotides bound to the QD surface. This study enables applications requiring the self-assembly of semiconductor-oligonucleotide hybrid materials and proves the conjugation success in a simple and straightforward manner.

Nanowires: Quantitative Probing of Cu(2+) Ions Naturally Present in Single Living Cells (Adv. Mater. 21/2016)

Quantitative probing of the Cu(2+) ions naturally present in single living cells is accomplished by a probe made from a quantum-dot-embedded-nanowire waveguide. After inserting the active nanowire-based waveguide probe into single living cells, J. H. Je and co-workers directly observe photoluminescence (PL) quenching of the embedded quantum dots by the Cu(2+) ions diffused into the probe as described on page 4071. This results in quantitative measurement of intracellular Cu(2+) ions.

Quantitative Probing of Cu(2+) Ions Naturally Present in Single Living Cells

Quantitative probing of Cu(2+) ions naturally present in single living cells is realized by developing a quantum-dot-embedded nanowire-waveguide probe. The intracellular Cu(2+) ion concentration is quantified by direct monitoring of photoluminescence quenching during the insertion of the nanowire in a living neuron. The measured intracellular Cu(2+) ion concentration is 3.34 ± 1.04 × 10(-6) m (mean ± s.e.m.) in single hippocampal neurons.