Self-Powered Circularly Polarized Light Detection Enabled by Chiral Two-Dimensional Perovskites with Mixed Chiral-Achiral Organic Cations.

Direct detection of circularly polarized light (CPL) holds great promise for the development of various optical technologies. Chiral 2D organic-inorganic halide perovskites make it possible to fabricate CPL-sensitive photodetectors. However, selectively detecting left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light remains a significant challenge. Herein, we demonstrate a greatly enhanced distinguishability of photodiode-type CPL photodetectors based on chiral 2D perovskites with mixed chiral aryl (R)-(+),(S)-(-)-α-methylbenzylammonium (R,S-MBA) and achiral alkyl n-butylammonium (nBA) cations. The (R,S-MBA0.5nBA0.5)2PbI4 perovskites exhibit a 10-fold increase in circular dichroism signals compared to (R,S-MBA)2PbI4 perovskites. The CPL photodetectors based on the mixed-cation perovskites exhibit self-powered capabilities with a specific detectivity of 2.45 × 1012 Jones at a 0 V bias. Notably, these devices show high distinguishability (gres) factors of -0.58 and +0.54 based on (R,S-MBA0.5nBA0.5)2PbI4 perovskites, respectively, surpassing the performance of (R-MBA)2PbI4-based devices by over 3-fold and setting a record for CPL detectors based on chiral 2D n = 1 perovskites.

Extracellular vesicles incorporating retrovirus-like capsids for the enhanced packaging and systemic delivery of mRNA into neurons.

The blood-brain barrier (BBB) restricts the systemic delivery of messenger RNAs (mRNAs) into diseased neurons. Although leucocyte-derived extracellular vesicles (EVs) can cross the BBB at inflammatory sites, it is difficult to efficiently load long mRNAs into the EVs and to enhance their neuronal uptake. Here we show that the packaging of mRNA into leucocyte-derived EVs and the endocytosis of the EVs by neurons can be enhanced by engineering leucocytes to produce EVs that incorporate retrovirus-like mRNA-packaging capsids. We transfected immortalized and primary bone-marrow-derived leucocytes with DNA or RNA encoding the capsid-forming activity-regulated cytoskeleton-associated (Arc) protein as well as capsid-stabilizing Arc 5'-untranslated-region RNA elements. These engineered EVs inherit endothelial adhesion molecules from donor leukocytes, recruit endogenous enveloping proteins to their surface, cross the BBB, and enter the neurons in neuro-inflammatory sites. Produced from self-derived donor leukocytes, the EVs are immunologically inert, and enhanced the neuronal uptake of the packaged mRNA in a mouse model of low-grade chronic neuro-inflammation.

Small to Large Polaron Behavior Induced by Controlled Interactions in Perovskite Quantum Dot Solids.

The polaron is an essential photoexcitation that governs the unique optoelectronic properties of organic-inorganic hybrid halide perovskites, and it has been subject to extensive spectroscopic and theoretical investigation over the past decade. A crucial but underexplored question is how the nature of the photogenerated polarons is impacted by the microscopic perovskite structure and what functional properties this affects. To tackle this question, we chemically tuned the interactions between perovskite quantum dots (QDs) to rationally manipulate the polaron properties. Through a suite of time-resolved spectroscopies, we find that inter-QD interactions open an excited-state channel to form large polaron species, which exhibit enhanced spatial diffusion, slower hot polaron cooling, and a longer intrinsic lifetime. At the same time, polaronic excitons are formed in competition via localized band-edge states, exhibiting strong photoluminescence but are limited by shorter intrinsic lifetimes. This control of polaron type and function through tunable inter-QD interactions not only provides design principles for QD-based materials but also experimentally disentangles polaronic species in hybrid perovskite materials.

Hydroxymethyl-Functionalized PEDOT-MeOH:PSS for Perovskite Solar Cells.

Poly(hydroxymethylated-3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT-MeOH:PSS) conducting polymers are synthesized and incorporated in inverted structured perovskite solar cells (PVSCs) as hole transport materials. The highest occupied molecular orbital of PEDOT-MeOH is lowered by adding a hydroxymethyl (-MeOH) functional group to ethylenedioxythiophene (EDOT), and thus, the work function of PEDOT-MeOH:PSS is increased. Additionally, hydrogen bonding can be formed among EDOT-MeOH monomers and between EDOT-MeOH monomers and sulfate groups on PSS, which promotes PEDOT-MeOH chain growth and enhances PSS doping. The electronic, microstructural, and surface morphological properties of PEDOT-MeOH:PSS are modified by changing the amounts of PSS and the ferric oxidizing agent used in the polymerization and by adding ethylene glycol in the postsynthesis treatment. The PVSCs based on ethylene-glycol-treated PEDOT-MeOH:PSS overperform the PVSCs based on commercial PEDOT:PSS because of the better energetic alignment and the enhancement of PEDOT-MeOH:PSS electrical conductivity. This work opens the way to develop new hole transport materials for highly efficient inverted PVSCs.

Plasmonic Gold Nanohole Array for Surface-Enhanced Raman Scattering Detection of DNA Methylation.

Surface-enhanced Raman spectroscopy (SERS), which utilizes nanogaps between noble-metal nanostructures as hot spots to yield ultrasensitive SERS signals, is an outstanding label-free and straightforward tool for DNA methylation analysis. Herein, a plasmonic gold nanohole array (PGNA) with well-controlled hot spots and an open surface was designed as a SERS substrate for DNA methylation detection. A finite-difference time-domain (FDTD) simulation was first employed to investigate the electric field distributions of the PGNA as a function of the geometric parameters. The plasmonic response was tuned to 785 cm-1 to match the ring breathing vibrational band of cytosine, the intensity change of which was revealed to be a marker of DNA methylation. Then, guided by the FDTD simulation results, the PGNA was fabricated via the electron beam lithography (EBL) technique. The fabricated PGNA had an open and easily accessible surface topology, a SERS enhancement factor of ∼106, and a relative standard deviation (RSD) of 7.1% for 500 repetitions over an area of 20 × 20 µm2 using 1 µM Rhodamine 6G as the Raman reporter. The fabricated PGNA was further used as a platform for determining DNA methylation. The proposed method exhibited a sensitivity for detecting 1% of methylation changes. Moreover, insight into the dynamic information on methylation events was obtained by combining principal component analysis (PCA) with 2D correlation spectroscopy analysis. Finally, clear discrimination of the different methylation sites, such as 5-methylcytosine and N6-methyladenine, was demonstrated.

Label-Free Raman Observation of TET1 Protein-Mediated Epigenetic Alterations in DNA.

Epigenetic modifications of DNA are known to modulate gene activity and expression and are believed to result in genetic diseases, such as cancer. Four modified cytosines were discovered in mammalian genomes: 5-methycytoine (5mC), 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxycytosine (5caC). They are regarded as DNA epigenetic markers and play key roles in the regulation of the dynamic balance between DNA methylation and demethylation. Although detection approaches toward 5mC are ubiquitous, few assays have reported the simultaneous determination of all four modified cytosines as well as monitoring of their dynamic alterations. Here, we developed a label-free surface enhanced Raman spectroscopy (SERS)-based method for directly sensing the four DNA modifications by using a plasmonic gold nanohole array (PGNA) with well-controlled hot spots and an open surface as the substrate. This method is based on identifying SERS spectral features resulting from DNA base modifications. Our study shows that 5mC, 5hmC, 5fC, and 5caC exhibit distinct Raman spectroscopic signatures at 785, 660, 1450, and 1680 cm-1, respectively. Moreover, the developed method can be used for tracking of the dynamic alterations among these four modified cytosines in DNA mediated by the ten-eleven translocation (TET) protein. The dynamic stepwise conversion from 5mC into 5hmC, 5fC, and 5caC is further demonstrated to be a typical three-step consecutive reaction with rate constants of 0.6, 0.25, and 0.15 min-1, respectively, which has not been achieved before via a SERS-based method.

Sensitive Bacterial Detection via Dielectrophoretic-Enhanced Mass Transport Using Surface-Plasmon-Resonance Biosensors.

The performance of surface plasmon resonance (SPR)-based bacterial biosensors is often compromised as a result of diffusion-limited mass transport of bacteria to the sensing surface. In this work, dually functional interdigitated electrodes (IDEs) were developed to sustain SPR and increase bacterial mass transport through external application of dielectrophoresis (DEP). IDEs were defined into 50 nm Au films with fixed electrode gaps ( EG = 5 µm) and varied electrode widths ( EW = 10, 20, and 100 µm),  referred to as interdigitated SPR (iSPR) chips. The iSPR chips with EW = 100 µm effectively supported SPR, with comparable sensitivity to those of conventional SPR chips. The surfaces of iSPR chips ( EW = 100 µm) were modified with mannose to target the FimH adhesin of Escherichia coli and increase cellular adhesion. An LOD of ∼3.0 × 102 CFU/mL E. coli was achieved on mannosylated iSPR chips under positive-DEP conditions, which is about a 5 order of magnitude improvement compared with those of mannosylated conventional SPR chips without DEP. Furthermore, secondary antibody amplification enabled selective enhancement of dilute (103 CFU/mL) E. coli suspensions, whereas no amplification was observed for concentrated (108 CFU/mL) nontarget ( Staphylococcus epidermidis) bacterial suspensions. The results presented here indicate the great potential of the incorporation of DEP into SPR biosensors for rapid, sensitive, and specific detection of bacteria with broad applications in areas of biomedical diagnostics, environmental monitoring, food safety, and homeland security.

Narrowband Ultraviolet Photodetectors Based on Nanocomposite Thin Films with High Gain and Low Driving Voltage.

Narrowband ultraviolet (UV) photodetectors are highly desired in multiple areas. Photodetectors based on organic-inorganic nanocomposites offer high sensitivity, widely adjustable response range, light weight, and low-temperature solution processibility. However, the broad absorption range of organic and inorganic semiconductor materials makes it difficult to achieve a narrowband detection feature for nanocomposite photodetectors. In this work, nanocomposite thin films containing the wide band gap conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)- alt- co-(bithiophene)] (F8T2) blended with wide band gap ZnO nanoparticles (NPs) serve as the active layers of the photodetectors. Narrowband UV photodetectors with high gain and low driving voltage are demonstrated by adopting a symmetric device structure, controlling the active layer composition and microstructure, and manipulating the light penetration depth in the active layer. The fabricated photodetector exhibits a high external quantum efficiency of 782% at 358 nm under a low forward bias of 3 V with the full-width at half-maximum of 16 nm. Combined with a low dark current, a high specific detectivity of 8.45 × 1012 Jones is achieved. The impacts of the F8T2:ZnO NPs weight ratio and the device structure on the UV-selectivity and the device performance are investigated and discussed. Our method offers a pathway to design and fabricate narrowband UV photodetectors.

Flexible Narrowband Ultraviolet Photodetectors with Photomultiplication Based on Wide Band Gap Conjugated Polymer and Inorganic Nanoparticles.

Lightweight and flexible ultraviolet (UV) photodetectors (PDs) have wide applications and have attracted more attention. PDs using organic and inorganic nanocomposites as active layers with a photodiode configuration could achieve photomultiplication and narrowband photoresponse via the control of microstructure and thickness of active layers. Here, we fabricated flexible UV PDs on indium tin oxide-coated poly(ethylene terephthalate) substrates with a nanocomposite active layer composed of ZnO nanoparticles blended with a wide band gap conjugated polymer, poly[(9,9-dioctylfluorenyl-2,7-diyl)- alt- co-(bithiophene)] (F8T2). As a result of the wavelength-dependent penetration depth of light in the active layer, the fabricated flexible UV PDs showed two narrow response peaks at 360 and 510 nm under reverse biases in the external quantum efficiency (EQE) spectra with full width at half maximum (FWHM) less than 20 nm. Both responses exhibited greater than 100% EQE, indicating a photomultiplication effect, whereas the UV response at 360 nm was 10 times stronger under -15 V bias. The fabricated flexible UV PDs were bent under both tensile and compressive stress to a curvature of 2.1 cm-1, each with 50 repetitions. The peak specific detectivity ( D*) only decreased by about 5% in total, the FWHM was well retained below 20 nm and the response speed remained almost constant after two types of bending, demonstrating mechanical flexibility and photoresponse stability of the fabricated flexible UV PDs. The photodiode configuration with nanocomposite active layers offers a promising route to make flexible and conformable narrowband, photomultiplication-type photodetectors for modern applications.

Tuning the spectral response of ultraviolet organic-inorganic hybrid photodetectors via charge trapping and charge collection narrowing.

Organic-inorganic hybrid ultraviolet photodetectors with tunable spectral response are desirable for many different applications. In this work, we blended poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) with ZnO nanoparticles in weight ratios of 1 : 1 and 2 : 1 to create charge traps within the active layers for devices with the conventional structure ITO/PEDOT : PSS/PTAA : ZnO/BCP/Al. Thin (150-200 nm) and thick (1400-1900 nm) active layers were employed to utilize charge collection narrowing (CCN). Both thickness and composition of the active layer impacted the spectral tunability of the photoresponse. A single narrow response peak centered at 420 nm (the PTAA absorption edge) with a full width at half maximum of 12 nm was achieved from the device with a 1900 nm active layer and PTAA : ZnO weight ratio of 1 : 1. Decreasing the active layer thickness to 150 nm resulted in a broad spectral response between 320-420 nm with an external quantum efficiency (EQE) value of 295% under 350 nm illumination and a -1 V bias, exhibiting photomultiplication via charge trapping and injection even at small reverse biases. Increasing the weight ratio of PTAA : ZnO to 2 : 1 lowered both the dark current and photocurrent, eliminated photomultiplication in the thin device, and diminished the efficacy of CCN to narrow the spectral photoresponse in the thick device. Transfer matrix method (TMM) and 3-dimensional finite-difference time-domain (3D-FDTD) simulations were performed to understand the impact of thickness and composition of the active layer on the spectral response of UV photodetectors in terms of exciton generation rate and electric field distribution within the devices.

Surface-Enhanced Raman Scattering for Rapid Detection and Characterization of Antibiotic-Resistant Bacteria.

As the prevalence of antibiotic-resistant bacteria continues to rise, biosensing technologies are needed to enable rapid diagnosis of bacterial infections. Furthermore, understanding the unique biochemistry of resistance mechanisms can facilitate the development of next generation therapeutics. Surface-enhanced Raman scattering (SERS) offers a potential solution to real-time diagnostic technologies, as well as a route to fundamental, mechanistic studies. In the current review, SERS-based approaches to the detection and characterization of antibiotic-resistant bacteria are covered. The commonly used nanomaterials (nanoparticles and nanostructured surfaces) and surface modifications (antibodies, aptamers, reporters, etc.) for SERS bacterial detection and differentiation are discussed first, and followed by a review of SERS-based detection of antibiotic-resistant bacteria from environmental/food processing and clinical sources. Antibiotic susceptibility testing and minimum inhibitory concentration testing with SERS are then summarized. Finally, recent developments of SERS-based chemical imaging/mapping of bacteria are reviewed.

Paper Sensor Coated with a Poly(carboxybetaine)-Multiple DOPA Conjugate via Dip-Coating for Biosensing in Complex Media.

Cellulose paper is an ideal diagnostic platform for low-cost, easily disposable and lightweight implementation, but requires surface modification to achieve detection with high sensitivity and specificity in complex media. In this work, a polymer-catechol conjugate containing a superhydrophilic nonfouling poly(carboxylbetaine) (pCB) and four surface-binding l-3,4-dihydroxyphenylalanine (DOPA) groups, pCB-(DOPA)4, were applied onto a paper-based sensor surface via a simple "graft-to" immersion process to render the surface with both nonfouling and protein functionalizable properties. This dip-coating technique is effective, convenient and robust as compared to the "graft-from" techniques reported previously with similar nonfouling properties. The coated paper sensor showed both increased analyte diffusion rate and improved sensitivity of glucose detection in human blood serum. The capability of pCB-(DOPA)4-modified paper sensor for specific antigen-antibody detection was demonstrated via the covalent immobilization of bovine serum albumin antibody (anti-BSA) and fibrinogen antibody (anti-Fg) onto the pCB-coated surface via simple 1-ethyl-3-(3-(dimethylamino)propyl)-carbodiimide and N-hydroxysuccinimide (EDC/NHS) chemistry.

Long-range surface plasmon resonance and surface-enhanced Raman scattering on X-shaped gold plasmonic nanohole arrays.

A multilayered architecture including a thin Au film supporting an X-shaped nanohole array and a thick continuous Au film separated by a Cytop dielectric layer is reported in this work. Long-range surface plasmon resonance (LR-SPR) was generated at the top Au/water interface, which also resulted in a long-range surface-enhanced Raman scattering (LR-SERS) effect. LR-SPR originates from the coupling of surface plasmons (SPs) propagating along the opposite sides of the thin Au film embedded in a symmetric refractive index environment with Cytop (n = 1.34) and water (n = 1.33). The finite-difference time-domain (FDTD) simulation method was used to investigate the optimal dimensions of the substrate by studying the reflectance spectra and electric field profiles. The calculated optimal structure was then fabricated via electron beam lithography, and its LR-SERS performance was demonstrated by detecting rhodamine 6G and 4-mercaptobenzoic acid in the refractive index-matched environment. We believe that this structure as a LR-SPR or LR-SERS substrate can have broad applications in biosensing.

Multi-functional, thiophenol-based surface chemistry for surface-enhanced Raman spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) has been recognized as one of the most sensitive sensing technologies and has been used for a variety of chemical, biological and medical applications. Compared to traditional direct SERS detection using a bare metal SERS-active substrate, surface chemistries and surface modifications on SERS-active substrates are becoming more and more important to achieve the detection of target analytes with a small surface affinity or weak Raman activity. As one special class of surface chemistries and modifications for SERS-active substrates, the thiophenol-based molecules offer new functions, increased sensitivity, and improved specificity to SERS-based sensing. The thiol group helps to form a stable modification on the gold or silver surface of SERS-active substrates, the benzene ring is used to report and amplify the detection signal, and the specific functional group on each thiophenol-based molecule contributes to the detection specificity. This article highlights the recent advances in thiophenol-based surface chemistry for SERS applications. The use of thiophenol-based molecule modified SERS-active substrates for fundamental studies, surface catalysis investigations and chemical and biological sensing is comprehensively discussed.

Design and development of plasmonic nanostructured electrodes for ITO-free organic photovoltaic cells on rigid and highly flexible substrates.

Indium tin oxide (ITO) is the most common transparent electrode used in organic photovoltaics (OPVs), yet limited indium reserves and poor mechanical properties make it non-ideal for large-scale OPV production. To replace ITO, we designed, fabricated, and deployed plasmonic nanostructured electrodes in inverted OPV devices. We found that active layer absorption is significantly impacted by ZnO thickness which affects the optical field distribution inside the resonant cavity formed between the plasmonic nanostructured electrode and top electrode. High quality Cr/Au nanostructured electrodes were fabricated by nanoimprint lithography and deployed in ITO-free inverted devices on glass. Devices with thinner ZnO showed a PCE as high as 5.70% and higher J SC's than devices on thicker ZnO, in agreement with finite-difference time-domain simulations. In addition, as the active layer was made optically thin, ITO-based devices showed diminished J SC while the resonant cavity effect from plasmonic nanostructured electrodes retained J SC. Preliminary ITO-free, flexible devices on PET showed a PCE of 1.82% and those fabricated on ultrathin and conformable Parylene substrates yielded an initial PCE over 1%. The plasmonic electrodes and device designs in this work show promise for developing highly functioning conformable devices that can be applied to numerous needs for lightweight, ubiquitous power generation.

Hierarchical zwitterionic modification of a SERS substrate enables real-time drug monitoring in blood plasma.

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive analytical technique with molecular specificity, making it an ideal candidate for therapeutic drug monitoring (TDM). However, in critical diagnostic media including blood, nonspecific protein adsorption coupled with weak surface affinities and small Raman activities of many analytes hinder the TDM application of SERS. Here we report a hierarchical surface modification strategy, first by coating a gold surface with a self-assembled monolayer (SAM) designed to attract or probe for analytes and then by grafting a non-fouling zwitterionic polymer brush layer to effectively repel protein fouling. We demonstrate how this modification can enable TDM applications by quantitatively and dynamically measuring the concentrations of several analytes-including an anticancer drug (doxorubicin), several TDM-requiring antidepressant and anti-seizure drugs, fructose and blood pH-in undiluted plasma. This hierarchical surface chemistry is widely applicable to many analytes and provides a generalized platform for SERS-based biosensing in complex real-world media.

Ultra-low fouling and high antibody loading zwitterionic hydrogel coatings for sensing and detection in complex media.

UNLABELLED: For surface-based diagnostic devices to achieve reliable biomarker detection in complex media such as blood, preventing nonspecific protein adsorption and incorporating high loading of biorecognition elements are paramount. In this work, a novel method to produce nonfouling zwitterionic hydrogel coatings was developed to achieve these goals. Poly(carboxybetaine acrylamide) (pCBAA) hydrogel thin films (CBHTFs) prepared with a carboxybetaine diacrylamide crosslinker (CBAAX) were coated on gold and silicon dioxide surfaces via a simple spin coating process. The thickness of CBHTFs could be precisely controlled between 15 and 150nm by varying the crosslinker concentration, and the films demonstrated excellent long-term stability. Protein adsorption from undiluted human blood serum onto the CBHTFs was measured with surface plasmon resonance (SPR). Hydrogel thin films greater than 20nm exhibited ultra-low fouling (<5ng/cm(2)). In addition, the CBHTFs were capable of high antibody functionalization for specific biomarker detection without compromising their nonfouling performance. This strategy provides a facile method to modify SPR biosensor chips with an advanced nonfouling material, and can be potentially expanded to a variety of implantable medical devices and diagnostic biosensors. STATEMENT OF SIGNIFICANCE: In this work, we developed an approach to realize ultra-low fouling and high ligand loading with a highly-crosslinked, purely zwitterionic, carboxybetaine thin film hydrogel (CBHTF) coating platform. The CBHTF on a hydrophilic surface demonstrated long-term stability. By varying the crosslinker content in the spin-coated hydrogel solution, the thickness of CBHTFs could be precisely controlled. Optimized CBHTFs exhibited ultra-low nonspecific protein adsorption below 5ng/cm(2) measured by a surface plasmon resonance (SPR) sensor, and their 3D architecture allowed antibody loading to reach 693ng/cm(2). This strategy provides a facile method to modify SPR biosensor chips with an advanced nonfouling material, and can be potentially expanded to a variety of implantable medical devices and diagnostic biosensors.

Solvent-molecule-mediated manipulation of crystalline grains for efficient planar binary lead and tin triiodide perovskite solar cells.

Binary lead and tin perovskites offer the benefits of narrower band gaps for broader adsorption of solar spectrum and better charge transport for higher photocurrent density. Here, we report the growth of large, smooth crystalline grains of bianry lead and tin triiodide perovskite films via a two-step solution process with thermal plus solvent vapor-assisted thermal annealing. The crystalline SnxPb1-xI2 films formed in the first step served as the templates for the formation of crystalline CH3NH3SnxPb1-xI3 films during the second step interdiffusion of methylammonium iodide (MAI). Followed by dimethylsulfoxide (DMSO) vapor-assisted thermal annealing, small, faceted perovskite grains grew into large, smooth grains via the possible mechanism involving bond breaking and reforming mediated by DMSO solvent molecules. The absorption onset was extended to 950 and 1010 nm for the CH3NH3SnxPb1-xI3 perovskites with x = 0.1 and 0.25, respectively. The highest PCE of 10.25% was achieved from the planar perovskite solar cell with the CH3NH3Sn0.1Pb0.9I3 layer prepared via the thermal plus DMSO vapor-assisted thermal annealing. This research provides a way to control and manipulate film morphology, grain size, and especially the distribution of metal cations in binary metal perovskite layers, which opens an avenue to grow perovskite materials with desired properties to enhance device performance.

Inverted hybrid CdSe-polymer solar cells adopting PEDOT:PSS/MoO3 as dual hole transport layers.

Inverted CdSe quantum dots (QDs):poly (3-hexylthiophene) (P3HT) organic/inorganic hybrid solar cells (OIHSCs) with the PEDOT: PSS/MoO3 dual hole transport layers (HTLs) showed superior performance over those with a single HTL of PEDOT: PSS or MoO3. The enhanced electron blocking at the active layer/anode interface as well as the prevention of leakage current accounted for the enhancement in the efficiency of the solar cells with the dual HTLs. By adopting the inverted structure and using the dual HTLs, the resistive losses of the CdSe QDs:P3HT hybrid system at high illumination power were effectively prevented. Further study showed the structure of dual HTLs was applicable to the solar cells with CdSe QDs and nanorods (NRs) blended with poly(thienothiophene-co-benzodithiophenes)7-F20 (PTB7-F20).

Functionalized plasmonic nanostructure arrays for direct and accurate mapping extracellular pH of living cells in complex media using SERS.

The extracellular pH (pHe) of living cells is one of the major factors that influence cell behaviors including cycle progression, migration, and proliferation, as well as metastasis and invasion of tumor cells. Thus, accurate sensing and mapping of the pHe is still a critical yet challenging task in the study of pHe-dependent cell behaviors. In this work, we present a method to map pHe of living cells based on surface-enhanced Raman spectroscopy (SERS). We immobilized a pH probe molecule, 4-mercaptobenzoic acid (4-MBA), on a gold quasi three-dimensional plasmonic nanostructure array (Q3D-PNA) to enable an exceptionally sensitive and reproducible pH measurement. We prudentially investigated the influences of cations and complexity of detecting solutions on the responses of 4-MBA SERS spectra to pH variations to ensure the accuracy. Herein, a normal cell line (NIH/3T3) and a tumor cell line (HepG2) were cultured on the 4-MBA modified SERS substrates. Localized pHe was detected and mapped with good spatial resolution and pH sensitivity showing pHe domains on both cells. Moreover, the averaged pHe of tumor cells was shown to be more acidic compared with that of normal cells.