MicroRNAs are short noncoding RNAs consisting of 18–25 nucleotides that target specific mRNA moieties for translational repression or degradation, thereby modulating numerous biological processes. Although microRNAs have the ability to behave like oncogenes or tumor suppressors in a cell-autonomous manner, their exact roles following release into the circulation are only now being unraveled and it is important to establish sensitive assays to measure their levels in different compartments in the circulation. Here, an ultrasensitive localized surface plasmon resonance (LSPR)-based microRNA sensor with single nucleotide specificity was developed using chemically synthesized gold nanoprisms attached onto a solid substrate with unprecedented long-term stability and reversibility. The sensor was used to specifically detect microRNA-10b at the attomolar (10–18 M) concentration in pancreatic cancer cell lines, derived tissue culture media, human plasma, and media and plasma exosomes. In addition, for the first time, our label-free and nondestructive sensing technique was used to quantify microRNA-10b in highly purified exosomes isolated from patients with pancreatic cancer or chronic pancreatitis, and from normal controls. We show that microRNA-10b levels were significantly higher in plasma-derived exosomes from pancreatic ductal adenocarcinoma patients when compared with patients with chronic pancreatitis or normal controls. Our findings suggest that this unique technique can be used to design novel diagnostic strategies for pancreatic and other cancers based on the direct quantitative measurement of plasma and exosome microRNAs, and can be readily extended to other diseases with identifiable microRNA signatures.

This paper reports large bathochromic shifts of up to 260 meV in both the excitonic absorption and emission peaks of oleylamine (OLA)-passivated molecule-like (CdSe) nanocrystals caused by postsynthetic treatment with the electron accepting Cd(OCPh) complex at room temperature. These shifts are found to be reversible upon removal of Cd(OCPh) by N,N,N',N'-tetramethylethylene-1,2-diamine. H NMR and FTIR characterizations of the nanocrystals demonstrate that the OLA remained attached to the surface of the nanocrystals during the reversible removal of Cd(OCPh). On the basis of surface ligand characterization, X-ray powder diffraction measurements, and additional control experiments, we propose that these peak red shifts are a consequence of the delocalization of confined exciton wave functions into the interfacial electronic states that are formed from interaction of the LUMO of the nanocrystals and the LUMO of Cd(OCPh), as opposed to originating from a change in size or reorganization of the inorganic core. Furthermore, attachment of Cd(OCPh) to the OLA-passivated (CdSe) nanocrystal surface increases the photoluminescence quantum yield from 5% to an unprecedentedly high 70% and causes a 3-fold increase of the photoluminescence lifetime, which are attributed to a combination of passivation of nonradiative surface trap states and relaxation of exciton confinement. Taken together, our work demonstrates the unique aspects of surface ligand chemistry in controlling the excitonic absorption and emission properties of ultrasmall (CdSe) nanocrystals, which could expedite their potential applications in solid-state device fabrication.

Organic-inorganic hybrid perovskites, direct band-gap semiconductors have shown tremendous promise for optoelectronic device fabrication. We report the first colloidal synthetic approach to prepare ultrasmall (~1.5 nm diameter), white light emitting, organic-inorganic hybrid perovskite nanoclusters. The nearly pure white-light emitting ultrasmall nanoclusters were obtained by selectively manipulating the surface chemistry (passivating ligands and surface trap-states) and controlled substitution of halide ions. The nanoclusters displayed a combination of band-edge and broadband photoluminescence properties, covering a major part of the visible region of the solar spectrum with unprecedentedly large quantum yields of ~12% and photoluninescence lifetime of ~20 ns. The intrinsic white light emission of perovskite nanoclusters makes them ideal and low cost hybrid nanomaterials for solid-state lighting applications.The ever-increasing global demand for energy drives the need to discover highly efficient materials capable of saving energy in solid-state lighting (SSL) applications, such as light-emitting diodes (LEDs). 1,2 In this context, pure white-light emitting materials, and their subsequent uses in LED fabrication, will be a most effective way to reduce global power consumption. Currently, white-light LEDs are prepared by: (i) mixing single wavelength emitting organic phosphors, 3 and (ii) constructing multi-layer films composed of blue, green, and red color emitting semiconductor quantum dots (QDs). 4,5 However, the self-absorption process between different organic phosphors reduces device efficiency, a similar device characteristic that has also been observed for QD-based LEDs. Ultrasmall semiconductor nanoclusters (e.g., CdSe) display white-light, but they require expensive, complicated and high temperature synthetic methods. [6][7][8] Recently, white-light emitting bulk organic-inorganic perovskites were synthesized, 9,10 which would not only expand SSL research but also facilitate inexpensive LED fabrication. Scheme 1. Schematic Presentation of the Synthesis of White-Light Emitting Organolead Bromide Perovskite NanoclustersIn this communication, we report the first colloidal synthetic method to prepare white-light emitting, ultrasmall (~1.5 nm diameter) methylammonium lead bromide (MAPbBr3) perovskite nanoclusters (PNCs). Their synthesis is outlined in Scheme 1 and the detailed procedure is provided in the Electronic Supplementary Information (ESI) file. These PNCs display a combination of band-edge and broadband photoluminescence (PL) with a quantum yield (QY) of ~5% and PL lifetime of ~7 ns. We hypothesize that the broad emission properties originate from the presence of surface-related midgap trap-states. Furthermore, we showed selective manipulation of band-gap and trap-states via the preparation of mixed halide (MAPbClxBr3-x) PNCs through controlled anion exchange reactions enhanced both QY and PL lifetime at least two-fold. We believe these ultrasmall PNCs will provide fundamentally important informati...

Strong inter-nanocrystal electronic coupling is a prerequisite for delocalization of exciton wave functions and high conductivity. We report 170 meV electronic coupling energy of short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals (SNCs) in solution. Cryo-transmission electron microscopy analysis showed the formation of a pearl-necklace assembly of nanocrystals in solution with regular inter-nanocrystal spacing. The electronic coupling was studied as a function of CdSe nanocrystal size where the smallest nanocrystals exhibited the largest coupling energy. The electronic coupling in spin-cast thin-film (<200 nm in thickness) of poly(ethylene glycol) thiolate-coated CdSe SNCs was studied as a function of annealing temperature, where an unprecedentedly large, ~400 meV coupling energy was observed for 1.6 nm diameter SNCs, which were coated with a thin layer of poly(ethylene glycol) thiolates. Small-angle X-ray scattering measurements showed that CdSe SNCs maintained an order array inside the films. The strong electronic coupling of SNCs in a selforganized film could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device application. TOC GraphicOne sentence text: Strong inter-nanocrystal electronic coupling is demonstrated between short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals both in the colloidal state and as dry films on solid surfaces.3