Continuous precipitation-filtration process for initial capture of a monoclonal antibody product using a four-stage countercurrent hollow fiber membrane washing step.

The significant increase in product titers, coupled with the growing focus on continuous bioprocessing, has renewed interest in using precipitation as a low-cost alternative to Protein A chromatography for the primary capture of monoclonal antibody (mAb) products. In this work, a commercially relevant mAb was purified from clarified cell culture fluid using a tubular flow precipitation reactor with dewatering and washing provided by tangential flow microfiltration. The particle morphology was evaluated using an inline high-resolution optical probe, providing quantitative data on the particle size distribution throughout the precipitation process.

Ultra-fast excited-state dynamics of substituted -naphthalene azo moieties.

In this work we untangle the ultrafast deactivation of high-energy excited states in four naphthalene-based azo dyes. Through systematic photophysical and computational study, we observed a structure-property relationship in which increasing the electron donating strength of the substituent leads to longer lived excited states in these organic dyes and faster thermal reversion from the to configuration. In particular, azo dyes 1-3 containing less electron donating substituents show three distinct excited-state lifetimes of ∼0.

Elucidation of complex triplet excited state dynamics in Pd(II) biladiene tetrapyrroles.

Pd(II) biladienes have been developed over the last five years as oligotetrapyrrole complexes that support a rich triplet photochemistry. In this work, we have undertaken the first detailed photophysical interrogation of three homologous Pd(II) biladienes bearing different combinations of methyl- and phenyl-substituents on the frameworks' sp-hybridized -carbon (, the 10-position of the biladiene framework). These experiments have revealed unexpected excited-state dynamics that are dependent on the wavelength of light used to excite the biladiene.

Synthesis, Electrochemistry, and Photophysics of Pd(II) Biladiene Complexes Bearing Varied Substituents at the sp-Hybridized 10-Position.

A set of Pd(II) biladiene complexes bearing different combinations of methyl- and phenyl-substituents on the sp-hybridized -carbon (the 10-position of the biladiene framework) was prepared and studied. In addition to a previously described Pd(II) biladiene complex bearing geminal dimethyl substituents a the 10-position (), homologous Pd(II) biladienes bearing geminal methyl and phenyl substituents () and geminal diphenyl groups() were prepared and structurally characterized. Detailed electrochemical as well as steady-state and time-resolved spectroscopic experiments were undertaken to evaluate the influence of the substituents on the biladiene's tetrahedral -carbon.

Spin multiplicity effects in doublet singlet emission: the photophysical consequences of a single electron.

Ambient-stable fluorescent radicals have recently emerged as promising luminescent materials; however, tailoring their properties has been difficult due to the limited photophysical understanding of open-shell organic systems. Here we report the experimental and computational analysis of a redox pair of π-conjugated fluorescent molecules that differ by one electron. A π-dication () and π-radical cation () demonstrate different absorption spectra, but similar red emission ( = ∼630 nm), excitation maxima ( = ∼530 nm), fluorescence lifetimes (1-10 ns), and even excited-state (non-emissive) lifetimes when measured by transient absorption spectroscopy.

Proton-controlled non-exponential photoluminescence in a pyridylamidine-substituted Re(I) complex.

Chemical intuition and well-known design principles can typically be used to create ligand environments in transition metal complexes to deliberately tune reactivity for desired applications. However, intelligent ligand design does not always result in the expected outcomes. Herein we report the synthesis and characterization of a tricarbonyl rhenium (2,2'-bipyridine) 4-pyridylamidine, Re(4-Pam), complex with unexpected photophysical properties.

ZnS Ultrathin Interfacial Layers for Optimizing Carrier Management in SbS-based Photovoltaics.

Antimony chalcogenides represent a family of materials of low toxicity and relative abundance, with a high potential for future sustainable solar energy conversion technology. However, solar cells based on antimony chalcogenides present open-circuit voltage losses that limit their efficiencies. These losses are attributed to several recombination mechanisms, with interfacial recombination being considered as one of the dominant processes.

Adjusting Interfacial Chemistry and Electronic Properties of Photovoltaics Based on a Highly Pure SbS Absorber by Atomic Layer Deposition.

The combination of oxide and heavier chalcogenide layers in thin film photovoltaics suffers limitations associated with oxygen incorporation and sulfur deficiency in the chalcogenide layer or with a chemical incompatibility which results in dewetting issues and defect states at the interface. Here, we establish atomic layer deposition (ALD) as a tool to overcome these limitations. ALD allows one to obtain highly pure SbS light absorber layers, and we exploit this technique to generate an additional interfacial layer consisting of 1.

Short Excited-State Lifetimes Enable Photo-Oxidatively Stable Rubrene Derivatives.

A series of rubrene derivatives were synthesized and the influence of the side group in enhancing photo-oxidative stability was evaluated. Photo-oxidation half-lives were determined via UV-vis absorption spectroscopy, which revealed thiophene containing derivatives to be the most stable species. The electron affinity of the compounds did not correlate with stability as previously reported in literature.

Modulating absorption and charge transfer in bodipy-carbazole donor-acceptor dyads through molecular design.

Three bodipy-based (BDP = 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) donor-acceptor dyads were designed and synthesized, and their ground-state and photophysical properties were systematically characterized. The electronic coupling between the BDP chromophore and an electron-donating carbazole (Carb) moiety was tuned by attachment via the meso and the beta positions on the BDP core, and through the use of various chemical linkers (phenyl and alkynyl) to afford mesoBDP-Carb, mesoBDP-phen-Carb, and betaBDP-alk-Carb. meso-Substituted dyads were found to retain ground-state absorption features of the unsubstituted BDP.

Anthracene-based azo dyes for photo-induced proton-coupled electron transfer.

Herein, we report a new donor-acceptor system for photo-induced proton-coupled electron transfer (PCET) that leverages an azo linkage as the proton-sensitive component and anthracene as a photo-trigger. Electrochemistry shows a change in the reduction potential with addition of acid. However, photochemistry is invariant to the absence or presence of acid.