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1. Discrimination and Quantitation of Biologically Relevant Carboxylate Anions Using A [Dye•PAMAM] Complex

   https://doi.org/10.3390/s21113637  

   Xu, Yifei ; Bonizzoni, Marco ( June 2021 , Sensors)

   null (Ed.)

   Carboxylate anions are analytical targets with environmental and biological relevance, whose detection is often challenging in aqueous solutions. We describe a method for discrimination and quantitation of carboxylates in water buffered to pH 7.4 based on their differential interaction with a supramolecular fluorescent sensor, self-assembled from readily available building blocks. A fifth-generation poly(amidoamine) dendrimer (PAMAM G5), bound to organic fluorophores (calcein or pyranine) through noncovalent interactions, forms a [dye•PAMAM] complex responsive to interaction with carboxylates. The observed changes in absorbance, and in fluorescence emission and anisotropy, were interpreted through linear discriminant analysis (LDA) and principal component analysis (PCA) to differentiate 10 structurally similar carboxylates with a limit of discrimination around 100 μM. The relationship between the analytes’ chemical structures and the system’s response was also elucidated. This insight allowed us to extend the system’s capabilities to the simultaneous identification of the nature and concentration of unknown analytes, with excellent structural identification results and good concentration recovery, an uncommon feat for a pattern-based sensing system. 

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2. Beta-Lactam Antibiotic Discrimination Using a Macromolecular Sensor in Water at Neutral pH

   https://doi.org/10.3390/s21196384  

   Xu, Yifei ; Bonizzoni, Marco ( October 2021 , Sensors)

   Penicillins and cephalosporins belong to the β-lactam antibiotic family, which accounts for more than half of the world market for antibiotics. Misuse of antibiotics harms human health and the environment. Here, we describe an easy, fast, and sensitive optical method for the sensing and discrimination of two penicillin and five cephalosporin antibiotics in buffered water at pH 7.4, using fifth-generation poly (amidoamine) (PAMAM) dendrimers and calcein, a commercially available macromolecular polyelectrolyte and a fluorescent dye, respectively. In aqueous solution at pH 7.4, the dendrimer and dye self-assemble to form a sensor that interacts with carboxylate-containing antibiotics through electrostatic interaction, monitored through changes in the dye’s spectroscopic properties. This response was captured through absorbance, fluorescence emission, and fluorescence anisotropy. The resulting data set was processed through linear discriminant analysis (LDA), a common pattern-base recognition method, for the differentiation of cephalosporins and penicillins. By pre-hydrolysis of the β-lactam rings under basic conditions, we were able to increase the charge density of the analytes, allowing us to discriminate the seven analytes at a concentration of 5 mM, with a limit of discrimination of 1 mM. 

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3. Development of Indium-tin Oxide Thin Films on PAMAM Dendrimer Layers for Perovskite Solar Cells Application

   Firdos Ali, Alecsander D. ( February 2023 , Energy Technology 2023)

   Despite the dramatic progress that has been made in the power-conversion efficiency (PCE) of perovskite solar cells (PVSCs), there are still many obstacles to be overcome before these devices can be economically competitive in the photovoltaics market. One of the major hurdles in the commercialization of PVSCs is low stability, which severely limits the effective lifetime of the devices. One of the approaches to achieving higher stability and lifetime of PVSCs is improvement of PVSC film quality. In this paper, we have employed a PAMAM dendrimer layer to reduce the surface roughness of sputter-deposited indium-tin oxide (ITO) films, which were then used in the fabrication of PVSCs. A PAMAM-8 dendrimer layer was deposited by dip-coating the substrates in 25 mL of a 1 μMPAMAM-8 ethanol solution before ITOdeposition. X-ray refractivity (XRR)was used to verify the PAMAMlayer on the substrate. ITOfilms of 150 nm thicknesswere then deposited onto the PAMAMlayer using DC magnetron reactive sputtering. The surface roughness, sheet resistance, and transmissivity of the ITO films were optimized by varying the parameters of the sputtering process. Atomic force microscopy (AFM) was used to measure the surface roughness of the ITO films with and without PAMAM dendrimer layer. A root-mean-square (RMS) film roughness of 1.6 nm, sheet resistance of 21 /ϒ, and transmissivity of > 91% at a wavelength of 400–700 nm were obtained after optimization. 

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4. Spectroscopic Characterization of the Divalent Metal Docking Motif to Isolated Cyanobenzoate: Direct Observation of Tridentate Binding to ortho -Cyanobenzoate and Implications for the CN Response

   https://doi.org/10.1021/acs.jpca.2c07658  

   Mohamed, Ahmed ; Edington, Sean C. ; Secor, Maxim ; Breton, James R. ; Hammes-Schiffer, Sharon ; Johnson, Mark A. ( February 2023 , The Journal of Physical Chemistry A)

   Cryogenic infrared vibrational spectroscopy of D2-tagged cyanobenzoate (CBA) derivatives are obtained and analyzed to characterize the intrinsic spectroscopic responses of the -CO2‾ head group to its location on the ring in both the isolated anions and the cationic complexes with divalent metal ions, M2+ (M=Mg, Ca, Sr). The benzonitrile functionality establishes the different ring isomers (para, meta, ortho) according to the location of the carboxylate and provides an additional reporter on the molecular response to the proximal charge center. The aromatic carboxylates display slightly smaller shifts than those observed for a related aliphatic system upon metal ion complexation. Although the CBA anions display very similar band patterns for all three ring positions, upon complexation with metal ions, the ortho isomer yields dramatically different spectral responses in both the -CO2‾ moiety and the CN group. This behavior is traced to the emergence of a tridentate binding motif unique to the ortho isomer in which the metal ions bind to both the oxygen atoms of the carboxylate group and the N atom of the cyano group. In that configuration, the -CO2‾ moiety is oriented perpendicular to the phenyl ring, and the CN stretching fundamental is both strong and red-shifted relative to its behavior in the isolated neutral. The behaviors of the metal-bound ortho complexes occur in contrast to the usual blue shifts associated with “Lewis” type binding of metal ions end-on to -CN. The origins of these spectroscopic features are analyzed with the aid of electronic structure calculations, which also explore differences expected for complexation of monovalent cations to the ortho carboxylate. The resulting insights have implications for understanding the balance between electrostatic and steric interactions at metal binding sites in chemical and biological systems. 

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5. Spatial Effect on the Performance of Carboxylate Anode Materials in Na‐Ion Batteries

   https://doi.org/10.1002/smll.202308113  

   Huang, Jinghao ; Li, Shi ; Wang, You ; Kim, Eric Youngsam ; Yang, Zhenzhen ; Chen, Dongchang ; Cheng, Lei ; Luo, Chao ( November 2023 , Small)

   Developing low‐voltage carboxylate anode materials is critical for achieving low‐cost, high‐performance, and sustainable Na‐ion batteries (NIBs). However, the structure design rationale and structure‐performance correlation for organic carboxylates in NIBs remains elusive. Herein, the spatial effect on the performance of carboxylate anode materials is studied by introducing heteroatoms in the conjugation structure and manipulating the positions of carboxylate groups in the aromatic rings. Planar and twisted organic carboxylates are designed and synthesized to gain insight into the impact of geometric structures to the electrochemical performance of carboxylate anodes in NIBs. Among the carboxylates, disodium 2,2’‐bipyridine‐5,5’‐dicarboxylate (2255‐Na) with a planar structure outperforms the others in terms of highest specific capacity (210 mAh g⁻¹), longest cycle life (2000 cycles), and best rate capability (up to 5 A g⁻¹). The cyclic stability and redox mechanism of 2255‐Na in NIBs are exploited by various characterization techniques. Moreover, high‐temperature (up to 100 °C) and all‐organic batteries based on a 2255‐Na anode, a polyaniline (PANI) cathode, and an ether‐based electrolyte are achieved and exhibited exceptional electrochemical performance. Therefore, this work demonstrates that designing organic carboxylates with extended planar conjugation structures is an effective strategy to achieve high‐performance and sustainable NIBs.

    

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