Eco-Friendly Pretreatment of Cotton Fabric With Banana Ash and Dyeing Using Banana Sap

The aim of this study is to evaluate environment supportive pretreatment and dyeing process. In this project, pretreatment of cotton fabric was done by using banana ash. Also, dyeing was carried out with banana sap along with different mordants that are eco-friendly and cost saving. Here, all the experiments were carried out on woven (plain) fabric of 141 GSM. Firstly, cotton fabric was scoured by means of banana root’s ash (pH-10.2). It was then dyed with banana sap (pH-5.4). This banana ash scoured cotton fabric was compared with conventionally scoured cotton fabric through weight loss % and absorbency test. In addition, fastness properties and performance of dyeing were measured through CIE L*C*h, K/S value, and different color fastness tests. Banana ash scoured and dyed with banana sap, using mordant (horitoky), provided the best dyeing performance and color fastness to wash, rubbing, and perspiration than the others

ISAP+: ISAP with Fast Authentication

This paper analyses the lightweight, sponge-based NAEAD mode $\textsf{ISAP}$, one of the finalists of the NIST Lightweight Cryptography (LWC) standardisation project, that achieves high-throughput with inherent protection against differential power analysis (DPA). We observe that $\textsf{ISAP}$ requires $256$-bit capacity in the authentication module to satisfy the NIST LWC security criteria. In this paper, we study the analysis carefully and observe that this is primarily due to the collision in the associated data part of the hash function which can be used in the forgery of the mode. However, the same is not applicable to the ciphertext part of the hash function because a collision in the ciphertext part does not always lead to a forgery. In this context, we define a new security notion, named $\textsf{2PI+}$ security, which is a strictly stronger notion than the collision security, and show that the security of a class of encrypt-then-hash based MAC type of authenticated encryptions, that includes $\textsf{ISAP}$, reduces to the $\textsf{2PI+}$ security of the underlying hash function used in the authentication module. Next we investigate and observe that a feed-forward variant of the generic sponge hash achieves better $\textsf{2PI+}$ security as compared to the generic sponge hash. We use this fact to present a close variant of $\textsf{ISAP}$, named $\textsf{ISAP+}$, which is structurally similar to $\textsf{ISAP}$, except that it uses the feed-forward variant of the generic sponge hash in the authentication module. This improves the overall security of the mode, and hence we can set the capacity of the ciphertext part to $192$ bits (to achieve a higher throughput) and yet satisfy the NIST LWC security criteria

Exploring Structure-Function Relationship in Small-Molecular Catalysts Using Computational and Experimental Methodologies

Molecular modeling is a useful tool in the field of catalyst design for various processes. The use of Density Functional Theory (DFT) is routine in almost every discipline of chemistry. This allows for a deeper understanding of a molecular system even in situations where implementation of an experimental technique is unfeasible. However, without the right choice of theory and insufficient description, the model becomes susceptible to produce ambiguous results. This often leads to poor correlation with experimental findings hence an incomplete understanding of the system under study. Hence, to acquire a thorough knowledge of the intricacies involved in a system, a judicious survey of the molecular model is necessary. Explored herein are embodiments of four catalytic systems, combining computational and experimental techniques, to better understand the structure-function relationship. The systems of choice include twelve homoleptic, and two heteroleptic Ni(II) tris-pyridinethiolate water splitting catalysts, an organo-photocatalyst for aerobic oxidation of benzylic alcohols, and finally a series of eighteen diarylhalonium salts and diarylchalcogenides. The first chapter describes a detailed study on homoleptic water splitting catalysis that demonstrates the impact of intramolecular hydrogen bonding (H-bonding) on the pKa of octahedral tris-(pyridinethiolato)nickel (II), [Ni(PyS)3]-, commonly referred to as Ni(II) tris-pyridinethiolate. Protonation is a key step in catalytic proton reduction to produce hydrogen gas, and thus optimizing the catalyst\u27s pKa is critical for catalyst design. DFT calculations on a Ni(PyS)3]- catalyst, and eleven derivatives, demonstrate geometric isomer formation in the protonation step of the catalytic cycle. Through Quantum Theory of Atoms in Molecules (QTAIM), we show that the pKa of each isomer is driven by intramolecular H-bonding of the proton on the pyridyl N to a S on a neighboring thiopyridyl (PyS-) ligand. Experimental measurements used to determine the pKa and reduction potential (E0) of the catalysts support the formation of the geometric isomers upon protonation, although the isomers complicate understanding the experimental results. This work demonstrates that ligand modification via the placement of electron-donating (D) or electron-withdrawing (W) groups may have unexpected effects on the catalyst\u27s pKa due to intramolecular H bonding. This work suggests the possibility that modification of substituent placement on the ligands to manipulate H bonding in homogeneous metal catalysts could be explored as a tool to simultaneously target both desired pKa and E0 values in small molecular catalysts. In the subsequent chapter a strategy to fine-tune the efficiency of a water splitting Ni(PyS)3]- catalyst through heteroleptic ligand design was explored using a computational investigation of the complete catalytic mechanism. DFT calculations supported by topology analyses using QTAIM, show introduction of electron donating (D) -CH3 and electron withdrawing (W) -CF3 groups on the PyS- ligands of the same complex can tune the pKa and E0, simultaneously. Computational modeling of two heteroleptic nickel(II) tris-pyridinethiolate complexes with 2:1 and 1:2 ED and EW -CH3 and -CF3 group containing PyS- ligands, respectively, suggests that the ideal combination of EW to ED groups is 2:1. This work also outlines the possibility of formation of a large number of isomers after the protonation of one of the pyridyl N atoms as observed in the homoleptic catalysis, and suggests that it is important to carefully account for all possible geometric isomers in order to obtain unambiguous computational results. This work provides a roadmap for synthetic chemists to achieve a better water splitting catalyst that could work in elevated pH media with lower overpotential. The next chapter describes a novel reaction pathway to photochemically oxidize a benzylic alcohol using an organocatalyst, N-hydroxyphthalimide (NHPI), and allows for the simultaneous access to hydrogen peroxide (H2O2) as a value-added byproduct under metal-free conditions. Photocatalytic oxidation of alcohols using oxygen often proceeds through excitation of oxygen from its triplet ground state to the singlet excited state where, singlet oxygen (1O2) is produced by using a photosensitizer to excite oxygen. Through computational and experimental investigation of the process, we have evaluated that the process utilizes 1O2 as the oxidant, that converts NHPI to the active radical intermediate phthalimide-N-oxyl (PINO). PINO initiates the oxidation on the organic motif by the abstraction of a H atom. Understanding the process in greater detail using computational methodologies will allow for the design of more efficient photocatalysts that are capable of carrying out more complicated aerobic oxidations using greener methods which is of immense interest for both laboratory and industrial scale reactions. Finally, a series of diarylhalonium salts and isoelectronic diarylchalcogenides were studied. This chapter entails the deviation of the structural parameters of these compounds from the well-accepted three center-four electron (3c-4e) bonding model. The existing 3c-4e model describes the bonding in λ3-iodanes accurately, however, fails to account for any structural deviation based on the periodic trends for hypervalent halogens and chalcogens. To provide a better understanding of the bonding and properties such as halogen bonding, and Lewis acidity, a major restructuring of the existing bonding theory was required. That was achieved by the inclusion of computed s- /p- orbital mixing on the molecular orbitals directed toward the incoming substituents, based on qualitative Bent\u27s rule. The introduction of orbital mixing along with the electronegativity of the substituents in the revised bonding could account for both experimentally observed thermodynamic and kinetic reactivity of a series of halonium salts. This work entails the exploration of different chemical systems that utilizes appropriate molecular model using computational methodologies. The calculated results were compared with the experimental investigations and a good correlation was observed. The molecular models described herein can be extrapolated to structurally allied systems to gain a better understanding of the underlying structure-function relationships

Improved photodecarboxylation properties in zinc photocages constructed using m-nitrophenylacetic acid variants

The methoxy- and fluoro-derivatives of meta-nitrophenylacetic acid (mNPA) chromophores undergo photodecarboxylation with comparable quantum yields to unsubstituted mNPA, but uncage at red-shifted excitation wavelengths. This observation prompted us to investigate DPAdeCageOMe (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-methoxy-3-nitrophenyl)acetic acid) and DPAdeCageF (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-fluoro-3-nitrophenyl)acetic acid) as Zn2+ photocages. DPAdeCageOMe has a high quantum yield and exhibits other photophysical properties comparable to XDPAdeCage ({bis[(2-pyridyl)methyl]amino}(9-oxo-2-xanthenyl) acetic acid), the best perforiming Zn2+ photocage reported to date. Since the synthesis of DPAdeCageOMe is more straightforward than XDPACage, the new photocage will be a highly competitive tool for biological applications

Photocatalytic Aerobic Oxidation of Benzylic Alcohols and Concomitant Hydrogen Peroxide Production

The photochemical oxidation of benzylic alcohols using N-hydroxyphthalimide (NHPI) catalyst, with Rose Bengal as a singlet oxygen photosensitizer, and the production of hydrogen peroxide (H2O2) under metal-free conditions is presented. Computational and experimental investigations support 1O2 as the oxidant that converts NHPI to the active radical intermediate phthalimide-N-oxyl (PINO). This is a green alternative to current methods of H2O2 production

Simplification of the Potassium Ferrioxalate Actinometer Through Carbon Dioxide Monitoring

Abstract Chemical actinometry can be used to determine photons absorbed for a photochemical reaction, which is required to calculate the quantum yield. A photochemical reaction with a known quantum yield can be used as a relative standard for the determination of an unknown quantum yield for a light-driven reaction. Herein, we have developed a simplified approach to using the popular potassium ferrioxalate actinometer. Traditionally, the photoreduction of Fe(III) to Fe(II) is monitored by following the absorbance of Fe(II) by reacting aliquots of the actinometry solution with 9,10-phenanthroline to form a red colored complex. The multiple steps for this method make it tedious and vulnerable to errors, especially inadvertent light exposure. In lieu of spectroscopic measurements of the Fe(II) concentration, the production of CO2 was measured to determine the number of photons absorbed over time. CO2 production was measured in two different ways: by the pressure increase in a sealed system and the volume change by trapping the CO2. Both methods were considerably less laborious and showed agreeable results compared with the traditional spectroscopic method

Improved Photodecarboxylation Properties in Zinc Photocages Constructed using M‐nitrophenylacetic Acid Variants

The methoxy- and fluoro-derivatives of meta-nitrophenylacetic acid (mNPA) chromophores undergo photodecarboxylation with comparable quantum yields to unsubstituted mNPA, but uncage at red-shifted excitation wavelengths. This observation prompted us to investigate DPAdeCageOMe (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-methoxy-3-nitrophenyl)acetic acid) and DPAdeCageF (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-fluoro-3-nitrophenyl)acetic acid) as Zn2+ photocages. DPAdeCageOMe has a high quantum yield and exhibits other photophysical properties comparable to XDPAdeCage ({bis[(2-pyridyl)methyl]amino}(9-oxo-2-xanthenyl) acetic acid), the best perforiming Zn2+ photocage reported to date. Since the synthesis of DPAdeCageOMe is more straightforward than XDPACage, the new photocage will be a highly competitive tool for biological applications

Orbital Analysis of Bonding in Diarylhalonium Salts and Relevance to Periodic Trends in Structure and Reactivity

Diarylhalonium compounds provide new opportunities as reagents and catalysts in the field of organic synthesis. The three center, four electron (3c–4e) bond is a center piece of their reactivity, but structural variation among the diarylhaloniums, and in comparison with other λ3-iodanes, indicates that the model needs refinement for broader applicability. We use a combination of Density Functional Theory (DFT), Natural Bond Orbital (NBO) Theory, and X-ray structure data to correlate bonding and structure for a λ3-iodane and a series of diarylchloronium, bromonium, and iodonium salts, and their isoelectronic diarylchalcogen counterparts. This analysis reveals that the s-orbital on the central halogen atom plays a greater role in the 3c–4e bond than previously considered. Finally, we show that our revised bonding model and associated structures account for both kinetic and thermodynamic reactivity for both acyclic phenyl(mesityl)halonium and cyclic dibenzohalolium salts

Computational Investigation into Intramolecular Hydrogen Bonding Controlling the Isomer Formation and P of Octahedral Nickel(ii) Proton Reduction Catalysts

This work demonstrates the impact of intramolecular hydrogen bonding (H-bonding) on the calculated p of octahedral tris-(pyridinethiolato)nickel(II), [Ni(PyS)3]-, proton reduction catalysts. Density Functional Theory (DFT) calculations on a [Ni(PyS)3]- catalyst, and eleven derivatives, demonstrate geometric isomer formation in the protonation step of the catalytic cycle. Through Quantum Theory of Atoms in Molecules (QTAIM), we show that the p of each isomer is driven by intramolecular H-bonding of the proton on the pyridyl nitrogen to a sulfur on a neighboring ligand. This work demonstrates that ligand modification the placement of electron-donating (ED) or electron-withdrawing (EW) groups may have unexpected effects on the catalyst\u27s p due to intramolecular H-bonding and isomer formation. These factors need to be considered in computational work. This work suggests the possibility that modification of substituent placement on the ligands to manipulate H-bonding in homogeneous metal catalysts could be explored as a tool to simultaneously target both desired p and ° values in small molecule catalysts

Computational Investigation of the Mechanism of an Octahedral Ni(II) Proton Reduction Catalyst and Importance of Intramolecular Hydrogen Bonding

Water-splitting to make hydrogen gas is of extreme importance in the field of alternative energy research. Transition-metal complexes are capable of catalyzing the conversion of water to hydrogen at higher pH, with low overpotential. Our research focuses on the importance of intramolecular hydrogen bonding (H-bonding) on the pKa and thermodynamic stability of the catalytic intermediates of a well-known proton-reduction catalyst, nickel (II) tris-pyridinethiolate. Density Functional Theory (DFT) calculations on the parent catalyst and eleven derivatives demonstrate geometric isomer formation after the protonation step of catalysis. These isomers differ in the relative thermodynamic stabilities and pKa values, which can be attributed to the difference in the strength of a hydrogen-bonding interaction between the proton on the pyridyl nitrogen atom and a sulfur atom from a neighboring ligand. The H-bond strength is directly proportional to the thermodynamic stability and properties of the protonated intermediates, which is well-understood in bio-macromolecules (proteins), but relatively unexplored in small-molecule catalysts. This research demonstrates the significance of considering isomer formation while modeling the mechanism related to octahedral complexes. This work also indicates the prospect of ligand modification to manipulate H-bonding in homogeneous catalysis to simultaneously target both pKa and reduction potential values