Christopher M. MacNeill

High efficiency organic solar cells with spray coated active layers comprised of a low band gap conjugated polymer

Airbrush is a promising tool for large scale organic thin film deposition in photovoltaic devices fabrication. This paper reports a detailed study on solar cell performance using airbrush spray deposition for active layer composed with recently developed low band gap donor material poly[4,8-bis(1-pentylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-2,1,3-benzoxadiazole-4,7-diyl and [6,6]-phenyl-C61-butyric acid methyl ester. The effect of carrier solvent and substrate temperature on film morphology are studied; a formula in 1,2-dichlorobenzene sprayed at a substrate temperature of 80 °C is found to be the optimum condition that produces a peak power conversion efficiency of 5.8%.

Differential response of MCF7, MDA-MB-231, and MCF 10A cells to hyperthermia, silver nanoparticles and silver nanoparticle-induced photothermal therapy

Abstract Purpose: Silver nanoparticles (Ag NP) can generate heat upon exposure to infrared light. The in vitro response of breast cell lines to Ag NP, both with and without nanoparticle-induced heating was evaluated. Materials and methods: Ag NP heat generation, intracellular silver concentration, and cell viability of MDA-MB-231, MCF7, and MCF 10A breast cells with Ag NP alone, or after exposure to 0.79 or 2.94 W/cm2 of 800 nm light were evaluated. Results: The concentration of Ag NP to induce sufficient heat for cell death, upon exposure to 800 nm light, was 5–250 μg/mL. Clonogenics assay indicates a cytotoxic response of MCF7 (45% decrease) and MDA-MB-231 (80% decrease) cells to 10 µg/mL, whereas MCF 10A had a 25% increase. Without Ag NP, MDA-MB-231 cells were more susceptible to hyperthermia, compared to MCF7 and MCF 10A cells. Clonogenics assay of Ag NP-induced photothermal ablation demonstrated that MCF 10A cells have the highest survival fraction. MCF7 cells had more silver in the cytoplasm, MDA-MB-231 cells had more in the nuclei, and MCF 10A cells had equivalent concentrations in the cytoplasm and nuclei. Conclusions: Ag NP are effective photothermal agents. A secondary benefit is the differential response of breast cancer cells to Ag NP-induced hyperthermia, due to increased intracellular silver content, compared to non-tumorigenic breast epithelial cells.

REVIEW OF METAL, CARBON AND POLYMER NANOPARTICLES FOR INFRARED PHOTOTHERMAL THERAPY

The aim of this review is to provide an up-to-date overview of nanoparticles developed for use as photothermal therapy agents (PTT) over the past five years. The main emphasis is on nanoparticles that absorb near infrared (NIR) light for PTT of cancer. Mild hyperthermia, including drug delivery, versus thermal ablation is also discussed. Recent advances in the synthesis of highly anisotropic novel metal nanoparticles for PTT are described. New metals and metal oxide complexes, as well as the use of quantum dots for PTT and as imaging agents are newer areas of development that are explained. This review also highlights current progress in the development of carbon nanoparticles, including reduced graphene oxide for both thermal ablation as well as drug delivery. The review culminates in the recent use electrically conductive polymer nanoparticles for hyperthermia. The advantages and unique features of these contemporary nanoparticles being used for PTT are highlighted. The goal of the present work is to describe the recent evolution of nanoparticles for NIR stimulated PTT, and highlight the innovations and future directions.

Eradicating group A streptococcus bacteria and biofilms using functionalised multi-wall carbon nanotubes

Abstract Purpose: The aim of this study was to demonstrate that multi-wall carbon nanotubes can be functionalised with antibodies to group A streptoccocus (GAS) for targeted photothermal ablation of planktonic and biofilm residing bacteria. Materials and methods: Antibodies for GAS were covalently attached to carboxylated multi-wall carbon nanotubes and incubated with either planktonic or biofilm GAS. Bacterium was then exposed to 1.3 W/cm2 of 800 nm light for 10–120 s, and then serially diluted onto agar plates from which the number of colony forming units was determined. Photothermal ablation of GAS on the surface of full thickness ex vivo porcine skin and histological sectioning were done to examine damage in adjacent tissue. Results: Approximately 14% of the GAS antibody-functionalised nanotubes attached to the bacterium, and this amount was found to be capable of inducing photothermal ablation of GAS upon exposure to 1.3 W/cm2 of 800 nm light. Cell viability was not decreased upon exposure to nanotubes or infrared light alone. Compared to carboxylated multi-wall carbon nanotubes, antibody-labelled nanotubes enhanced killing in both planktonic and biofilm GAS in conjunction with infrared light. Analysis of GAS photothermally ablated in direct contact with ex vivo porcine skin shows that heat sufficient for killing GAS remains localised and does not cause collateral damage in tissue adjacent to the treated area. Conclusions: The results of this study support the premise that carbon nanotubes may be effectively utilised as highly localised photothermal agents with the potential for translation into the clinical treatment of bacterial infections of soft tissue.

Exploring Spray-Coating Techniques for Organic Solar Cell Applications

We have investigated spray coating as a novel processing method for organic solar cell fabrication. In this work, spraying parameters and organic solvent influences have been correlated with cell performance. Using airbrush fabrication, bulk heterojunction photovoltaic devices based on a new low band gap donor material: poly[(4,8-bis(1-pentylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-2,1,3-benzoxadiazole-4,7-diyl] with the C60-derivative (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as an acceptor, have achieved power conversion efficiencies over 3%. We show that airbrush fabrication can be carried out with simple solvents such as pristine 1,2-dichlorobenzene. Moreover, the influence of device active area has been studied and the 1 cm2 device by spray coating maintained an excellent power conversion efficiency of 3.02% on average.

Variation of the Side Chain Branch Position Leads to Vastly Improved Molecular Weight and OPV Performance in 4,8-dialkoxybenzo[1,2-b:4,5-b′]dithiophene/2,1,3-benzothiadiazole Copolymers

Through manipulation of the solubilizing side chains, we were able to dramatically improve the molecular weight (𝑀𝑤) of 4,8-dialkoxybenzo[1,2-b:4,5-b′]dithiophene (BDT)/2,1,3-benzothiadiazole (BT) copolymers. When dodecyl side chains (P1) are employed at the 4- and 8-positions of the BDT unit, we obtain a chloroform-soluble copolymer fraction with 𝑀𝑤 of 6.3 kg/mol. Surprisingly, by moving to the commonly employed 2-ethylhexyl branch (P2), 𝑀𝑤 decreases to 3.4 kg/mol. This is despite numerous reports that this side chain increases solubility and 𝑀𝑤. By moving the ethyl branch in one position relative to the polymer backbone (1-ethylhexyl, P3), 𝑀𝑤 is dramatically increased to 68.8 kg/mol. As a result of this 𝑀𝑤 increase, the shape of the absorption profile is dramatically altered, with 𝜆max = 637 nm compared with 598 nm for P1 and 579 nm for P2. The hole mobility as determined by thin film transistor (TFT) measurements is improved from ∼1×10−6 cm2/Vs for P1 and P2 to 7×10−4 cm2/Vs for P3, while solar cell power conversion efficiency in increased to 2.91% for P3 relative to 0.31% and 0.19% for P1 and P2, respectively.

Bis(μ-dithieno[3,2-b:2′,3′-d]thio­phene-2,6-dicarboxyl­ato-κ2O2:O6)bis­[bis­(1,10-phenanthroline-κ2N,N′)cobalt(II)] dimethyl­formamide disolvate

The asymmetric unit of the title compound, [Co2(C10H2O4S3)2(C12H8N2)4]·2C3H7NO, contains one half of the formula unit, with the rest generated by inversion. The cobalt ion sits in a slightly distorted octahedral environment and is ligated to four N atoms of two 1,10-phenanthroline molecules and to two O atoms of two dithieno[3,2-b:2′,3′-d]thiophene-2,6-dicarboxylate anions. The anions act as bridges between the CoII centers.