Nanoscale & Nanoscale Advances Blog

A new photo-induced polymer crosslinking strategy has been used to produce optoelectronic devices with improved performance by a group of Chinese researchers. This has allowed quantum dot LED devices to be fabricated on flexible plastic substrates as the scientists can avoid high temperature thermal annealing.

Developed at Soochow University and Shanghai Jiaotong University, the researchers believe this crosslinking strategy provides an excellent general method for improving film quality in solution-processed multi-layer LEDs and optoelectronic devices.

The improved efficiency of the devices has been ascribed to superior film surface morphology of the device layers, as the range of non-orthogonal solvents able to be used for solution processing is greatly broadened due to layer crosslinking. The device is based on a hole transport layer of conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4’-(N-(4-butylphenyl)))] (TFB), which is crosslinked with a bifunctional benzophenone, with the crosslinked hole transport layer device giving a 2 times higher efficiency than the device without layer crosslinking.

Fig. 1. New photochemical crosslinking method enables fabrication of novel all-solution-processed multilayer optoelectronic devices to improve device performance using both orthogonal and non-orthogonal solvents.

Read the article:

Crosslinked conjugated polymers as hole transport layers in high-performance quantum dot light-emitting diodes

Yatao Zou, Ying Liu, Muyang Ban, Qi Huang, Teng Sun, Qing Zhang,* Tao Song* and Baoquan Sun*

Nanoscale Horizons, 2017, DOI: 10.1039/C6NH00217J

Alexander Cook is a guest web writer for the RSC journal blogs. He is a PhD researcher in the Perrier group at the University of Warwick, focusing on polymer materials and their use in various applications. Follow him on twitter @alexcook222

Cancer remains the leading cause of death worldwide. Therefore, the importance of early screening of cancer can aid in the prevention and treatment. However, early onset of cancers can often produce limited or no symptoms. In this regard, researchers have turned their attention to miRNA biomarkers found in serum as potential biomarkers for cancer detection. At the onset of cancer, miRNA biomarkers often present at very low concentrations representing a big challenge for researchers to develop analytical tools that can achieve the sensitivity required.

Researchers from Nanjing, China and Georgia, USA have investigated surface enhanced Raman scattering (SERS) as a viable technique for the detection of 3 miRNA biomarkers related to lung cancer. To achieve this, the researchers used a silver nanorod (AgNR) array to provide the plasmonic enhancement required for SERS. The substrate was subsequently functionalised with molecular beacons (MBs) containing different Raman reporters (ROX, Cy5 and FAM) that are complementary to the miRNA targets. In the absence of miRNA target, the SERS signal remains high since the MBs, and, therefore, the Raman reporters, are orientated close to the AgNR substrate. However, when the MBs hybridise to the target sequence, the SERS signal drops in a concentration-related manner allowing quantitation of the target miRNAs in buffer and human serum. The limits of detection for the 3 biomarkers, miRNA-21/486/375, were 393, 176 and 144 aM, respectively.

This research highlights the advantages of using SERS for biomarker detection. The low sensitivity and ability to multiplex make SERS a promising analytical technique for future clinical analyses for cancer detection and other diseases.

Scheme 1 Schematic illustration of the preparation and application of the molecular beacon functionalized-SERS sensor for simultaneously measuring multiple miRNAs.

An ultrasensitive SERS sensor for simultaneous detection of multiple cancer-related miRNAs
C. Y. Song, Y. J. Yang, B. Y. Yang, Y. Z. Sun, Y. P. Zhao and L. H. Wang
Nanoscale, 2016, 8, 17365-17373

Dr Lee Barrett is a guest web writer for the Nanoscale blog. Lee is currently a postdoctoral researcher in the Centre for Molecular Nanometrology at the University of Strathclyde. His research is currently focused on the development of nanoparticle-based sensors and surface enhanced Raman scattering (SERS). Follow him on twitter @L_Bargie

Polyrotaxanes are an exciting class of materials that in recent years have found applications in self-healing materials, coatings, nanomedicine, and biomaterials. This interesting supramolecular polymer architecture conveys unusual and dynamic properties not found in conventional covalently bonded polymer materials.

Fig. 1 DLS (number) analysis of PRX 5 (0.1 mg mL−1 ) at pH 7.2 (continuous line) and the self-assembly of PRX 5 into SA-PRX 5 at pH 2 (dashed line).

Commercially available PEG of 10 and 20 kDa were threaded into CDs with two different threading degrees of 28% and 65%. The CDs were modified with succinic anhydride to give approximately 4 carboxylic acid groups per CD ring.

At neutral pH, the 28% threaded polyrotaxanes formed self-assembled nanoparticles due to movement of the CD units along polymer chains to form segregated regions of more hydrophobic CD in the core and PEG chains at the periphery. When the pH of the polymer solution was less than 3 the subsequently charged CDs electrostatically repel each other and the nanoparticles fall apart to give their corresponding unimolecular polyrotaxanes in an extended conformation. By cycling the pH of the polyrotaxane system, nanoparticles can be formed and disassembled up to three times.

These nanoparticles are proposed to be of interest and significance for oral drug delivery systems that could be responsive to the lumen of the stomach (pH 1 – 3.8), and thus release therapeutics when the nanoparticles dissociate at low pH values.

Nanoparticles assembled via pH-responsive reversible segregation of cyclodextrins in polyrotaxanes
Blaise L. Tardy, Shereen Tan, Henk H. Dam, Hirotaka Ejima, Anton Blencowe, Greg G. Qiao and Frank Caruso
Nanoscale, 2016, Advance Article, DOI: 10.1039/C6NR04841B

Alexander Cook is a guest web writer for the RSC journal blogs. He is a PhD researcher in the Perrier group at the University of Warwick, focusing on polymer materials and their use in various applications. Follow him on twitter @alexcook222