Semiconductor SERS enhancement enabled by oxygen incorporation

<p>Semiconductor-based surface-enhanced Raman spectroscopy (SERS) substrates represent a new frontier in the field of SERS. However, the application of semiconductor materials as SERS substrates is still seriously impeded by their low SERS enhancement and inferior detection sensitivity, especially for non-metal-oxide semiconductor materials. Herein, we demonstrate a general oxygen-incorporation-assisted strategy to magnify the semiconductor substrate–analyte molecule interaction, leading to significant increase in SERS enhancement for non-metal-oxide semiconductor materials. Oxygen incorporation in MoS₂ even with trace concentrations can not only increase enhancement factors by up to 100,000 folds compared with oxygen-unincorporated samples, but also endow MoS₂ with low limit of detection below 10^-7 M. Intriguingly, combined with the findings in previous studies, our present results indicate that both oxygen incorporation and extraction processes can result in SERS enhancement, probably due to the enhanced charge-transfer resonance as well as exciton resonance arising from the judicious control of oxygen admission in semiconductor substrate.</p

Morphology-Controlled Synthesis of Hybrid Nanocrystals <i>via</i> a Selenium-Mediated Strategy with Ligand Shielding Effect: The Case of Dual Plasmonic Au–Cu_2–<i>x</i>Se

Integrating a plasmonic metal and a semiconductor at the nanoscale is of great importance for exploring their optical coupling properties. However, the synthesis and fine structural control of such nanostructures remain challenging. Herein we report the facile aqueous-phase Se-mediated overgrowth of metal selenides onto Au nanocrystals. Taking plasmonic Cu_2–<i>x</i>Se as an example, the introduction of a Se template allows deposition of large Cu_2–<i>x</i>Se crystalline grains onto Au nanocrystal seeds in various shapes, including spheres, rods, and plates. Moreover, the configuration of Au–Cu_2–<i>x</i>Se hybrids can be tuned from core–shell to heterodimer structure by controlling the growth behavior of the Se template. Se overgrowth depends critically on the absorption strength of stabilizers on Au seeds: a strongly absorbing stabilizer inhibits isotropic overgrowth, which is in agreement with molecular dynamics simulations. The resultant Au–Cu_2–<i>x</i>Se hybrid nanocrystals possess multiple surface plasmon resonance modes. Finally, our synthetic strategy can be extended to prepare other Au–metal selenide hybrids such as Au–Ag₂Se and Au–CdSe with controllable morphologies

Experimental therapies with WP1066 in OVA-challenged chronic asthmatic mice.

<p>(<b>A</b>) OVA-challenge was performed in BALB/c mice as described [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077795#B28" target="_blank">28</a>]. WP1066 was administered by intraperitoneal injection at doses of 40mg/kg 1h before the OVA-challenge. Airway resistance was measured using increasing concentration of methacholine and assessed using the flexiVent system. Results are expressed as the mean of experiments done in triplicate ± the standard error of the mean (SEM) (<i>* p<0.05</i>, <i>**p>0.05 </i><i>vs </i><i>control</i>). (<b>B</b>) TSLP, p16, p21, Ki-67, α-SMA and collagen I protein expressions were analyzed, 200×. (<b>C</b>) Bimodal H score distribution of TSLP, p16, p21, Ki67, α-SMA and collagen I immunoperoxidase reactions are presented.</p

Cellular senescence is induced by TSLP stimulation <i>in</i><i>vitro</i>.

<p>(<b>A</b>) TSLP-induced p16 and p21 upregulation occurs in a TSLP dose-dependent manner in human bronchial epithelial BEAS-2B cells. BEAS-2B cells were stimulated with different doses of TSLP as indicated for 6h. Protein expressions of p16, p21 and phospho-Stat3 (Try705) were detected by western blotting. (<b>B</b>) BEAS-2B cells were stimulated by 1.5ng/ml TSLP and protein expressions of p16 and p21 were detected by western blotting. (<b>C</b>) BEAS-2B cells were stimulated with 1.5ng/ml TSLP then stained for BrdU. (<i>*p< 0.05</i>). BEAS-2B cells were stimulated with 1.5ng/ml TSLP then stained for SA-β-gal activity at 6 and 24 hours post stimulation. (<b>D</b>) upper panel: SA-β-gal staining; lower panel: quantification of SA-β-gal positive cells. (*<i>p</i> < 0.05); (<b>E</b>) Ki67 staining. (<b>F</b>) Levels of TSLP in culture media were examined by ELISA. </p

Senescent inhibition overcomes TSLP-induced airway remodeling in vitro.

<p>BEAS-2B cells with stable shp16, shp21 or both were incubated with TSLP (1.5ng/ml) for 6 h. (<b>A</b>) Cells were collected and total proteins were extracted and analyzed by western blotting. (<b>B</b>) Cells were fixed and stained with SA-β-gal (upper panel) and then positive SA-β-gal cells were quantified (<i>*p>0.05</i>, **<i>p</i> < 0.05) (low panel). (<b>C</b>) Cells were stained with BrdU (<i>*p>0.05</i>, **<i>p</i> < 0.05). (<b>D</b>) Senescent inhibition overcomes TSLP-induced cell growth inhibition in vitro. The relative cell number was detected to evaluate cell growth at different time points using MTT assays.</p

Active Manipulation of NIR Plasmonics: the Case of Cu_2–<i>x</i>Se through Electrochemistry

Active control of nanocrystal optical and electrical properties is crucial for many of their applications. By electrochemical (de)­lithiation of Cu_2–<i>x</i>Se, a highly doped semiconductor, dynamic and reversible manipulation of its NIR plasmonics has been achieved. Spectroelectrochemistry results show that NIR plasmon red-shifted and reduced in intensity during lithiation, which can be reversed with perfect on–off switching over 100 cycles. Electrochemical impedance spectroscopy reveals that a Faradaic redox process during Cu_2–<i>x</i>Se (de)­lithiation is responsible for the optical modulation, rather than simple capacitive charging. XPS analysis identifies a reversible change in the redox state of selenide anion but not copper cation, consistent with DFT calculations. Our findings open up new possibilities for dynamical manipulation of vacancy-induced surface plasmon resonances and have important implications for their use in NIR optical switching and functional circuits