Amid the investigation of solid-state dye-sensitized solar cells (SDSSCs), it was found that the incorporation of F4TCNQ into the solid hole-transporting materials (HTMs) spiro-MeOTAD forms a spiro-MeOTAD/F4TCNQ (strong electron acceptor) polaron charge-transfer complex. Careful examination indicates that the formation of the polaron charge-transfer complex not only facilitates the conductivity of HTMs but also inhibits the charge recombination across the interface of the heterojunction, i.e. photoanode/HTMs and/or counter electrode/HTMs. As a result, the performance of SDSSCs has been markedly improved by using the organic dye A2-F. At AM1.5 illumination the short circuit current densities J(SC) increase from 8.29 mA cm(-2) (w/o F4TCNQ) to 10.95 mA (w/F4TCNQ), accompanied by a 20% increase of the overall power conversion efficiency, η, from 4.55% to 5.44%.

bulk heterojunction (BHJ) confi guration has been attracting considerable interest due to their low-cost fabrication, mechanical fl exibility and potential to provide effi cient conversion of solar energy. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] There are a number of challenges on the way to achieve high power conversion effi ciency (PCE) of solar cells. These include the development of low bandgap conjugated polymers with respect to broad light absorption and effi cient charge separation/transportation via controlling the nanostructure of active layer. As a result, several highly effi cient polymers have been reported with high PCE surpassing than 7% to date. [7][8][9] Considering the power conversion processes, including solar light absorption, exciton generation, exciton dissociation, and charge carriers transport, all occur in the active layers. [17][18][19][20][21][22][23][24][25] Therefore, gaining insight into the nanostructure of the active layer and the corresponding morphology, [22][23][24][25] as well as the photovoltaic mechanism, [17][18][19][20][21] is benefi cial to meliorate the PCE of the resulting BHJ solar cells. It is well known that reducing recombination is a linchpin of increasing device effi ciency. [ 22 ] Therefore, decreasing the thickness of the active layer and maximizing its absorption capability to reduce the device resistance and the probability of charge recombination play key roles to improve the device's PCE. From this viewpoint, a remarkable amount of work has been devoted to utilizing metal nanoparticles (NPs) strategies that result from their localized surface plasmon resonance (LSPR) for effi cient light trapping in the active layer in an aim to enhance photon absorption without the need for a thick fi lm. [26][27][28] To date, most studies are focused on single-composition of gold, silver, and copper NPs, which are almost exclusively suspended in aqueous solution. [28][29][30] In comparison, much less systematic experimental study of alloying metal NPs has been performed in photo voltaic performance so far. [ 31 ] More importantly, conjugated polymers are soluble primarily in organic solvents, which are incompatible with aqueous media. This limits the use of these metal NPs in organic photovoltaic devices. Although many of the device geometries have been reported to directly introduce various species of aqueous phase metal NPs in poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) A one-pot synthesis of large size and high quality AuAg alloy nanoparticles (NPs) with well controlled compositions via hot organic media is demonstrated. Amid the synthesis, complexation between trioctylphosphine (TOP) and metal precursors is found, which slows down the rate of nucleation and leads to the growth of large-size AuAg nanoalloys. The wavelength and relative intensities of the resulting plasmon bands are readily fi ne-tuned during the synthetic process using different Au/Ag precursors molar ratios. In the polymer solar cells, a key step in achieving high effi ciency...

Mechanically triturated n- and p-type Bi2Te3 nanoparticles, the nanoscale topological insulators (TIs), are employed as nonlinear saturable absorbers to passively mode-lock the erbium-doped fiber lasers (EDFLs) for sub-400 fs pulse generations. A novel method is proposed to enable the control on the self-amplitude modulation (SAM) of TI by adjusting its dopant type. The dopant type of TI only shifts the Fermi level without changing its energy bandgap, that the n- and p-type Bi2Te3 nanoparticles have shown the broadband saturable absorption at 800 and 1570 nm. In addition, both the complicated pulse shortening procedure and the competition between hybrid mode-locking mechanisms in the Bi2Te3 nanoparticle mode-locked EDFL system have been elucidated. The p-type Bi2Te3 with its lower effective Fermi level results in more capacity for excited carriers than the n-type Bi2Te3, which shortens the pulse width by enlarging the SAM depth. However, the strong self-phase modulation occurs with reduced linear loss and highly nonsaturated absorption, which dominates the pulse shortening mechanism in the passively mode-locked EDFL to deliver comparable pulse widths of 400 and 385 fs with n- and p-type Bi2Te3 nanoparticles, respectively. The first- and second-order Kelly sidebands under soliton mode-locking regime are also observed at offset frequencies of 1.31 and 1.94 THz, respectively.

A novel T1 agent, antiferromagnetic α-iron oxide-hydroxide (α-FeOOH) nanocolloids with a diameter of 2-3 nm, has been successfully prepared. These nanocolloids, together with a post synthetic strategy performed in mesoporous silica, are a great improvement over the low T1-weighted contrast common in traditional magnetic silica nanocomposites. The intrinsic antiferromagnetic goethite (α-FeOOH) shows very low magnetization (M(z)) of 0.05 emu g(-1) at H = 2 T at 300 K (0.0006 emu g(-1) for FeOOH/WMSN-PEG), which is 2 orders of magnitude smaller than any current ultrasmall iron oxide NPs (>5 emu g(-1)) reported to date, hence ensuring the low r2 (∝ Mz) (7.64 mM(-1) s(-1)) and r2/r1 ratio (2.03) at 4.7 T. These biodegradable α-FeOOH nanocolloids also demonstrate excellent in vitro cellular imaging and in vivo MR vascular and urinary trace imaging capability with outstanding biocompatibility, which is exceptionally well secreted by the kidney and not the liver as with most nanoparticles, opening up a new avenue for designing powerful antiferromagnetic iron T1 contrast agents.

The room-temperature, aqueous-phase synthesis of iron-oxide nanoparticles (IO NPs) with glutathione (GSH) is reported. The simple, one-step reduction involves GSH as a capping agent and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the reducing agent; GSH is an anti-oxidant that is abundant in the human body while THPC is commonly used in the synthesis of noble-metal clusters. Due to their low magnetization and good water-dispersibility, the resulting GSH-IO NPs, which are 3.72 ± 0.12 nm in diameter, exhibit a low r2 relaxivity (8.28 mm(-1) s(-1)) and r2/r1 ratio (2.28)--both of which are critical for T1 contrast agents. This, together with the excellent biocompatibility, makes these NPs an ideal candidate to be a T1 contrast agent. Its capability in cellular imaging is illustrated by the high signal intensity in the T1-weighted magnetic resonance imaging (MRI) of treated HeLa cells. Surprisingly, the GSH-IO NPs escape ingestion by the hepatic reticuloendothelial system, enabling strong vascular enhancement at the internal carotid artery and superior sagittal sinus, where detection of the thrombus is critical for diagnosing a stroke. Moreover, serial T1- and T2-weighted time-dependent MR images are resolved for a rat's kidneys, unveiling detailed cortical-medullary anatomy and renal physiological functions. The newly developed GSH-IO NPs thus open a new dimension in efforts towards high-performance, long-circulating MRI contrast agents that have biotargeting potential.