Utilizing sulfa drugs' pH-dependent spectral modifications for designing molecular logic gates

In this study, the absorption and fluorescence characteristics of sulfa drugs, specifically Sulfadiazine (SDZ), Sulfamerazine (SMZ), and Sulfamethazine (STZ), were examined across a pH range of 1-14. The absorption and fluorescence spectra of these sulfa drugs showed significant changes depending on the pH value. Analysis of their pH-dependent absorption and fluorescence properties indicated that these sulfa drugs could used to design molecular logic gates. The absorption and fluorescence behaviors at various wavelength maxima were utilized to design IMPLICATION and Improved-INHIBIT (I-INHIBIT) molecular logic gates.

Low Molecular Weight Probe for Selective Sensing of PH and Cu2+ Working as Three INHIBIT Based Digital Comparator

A novel simple molecular chemosensor 2 was synthesized and examined for pH, cations and anions detection. At pH values higher than 10, probe 2 switches on a green emission where the excited state intramolecular proton transfer (ESIPT) is ceased. Also, the probe absorption spectrum shows a clear pH dependence, and the probe aqueous solution (ethanol/water = 1:2, borate buffer) responds selectively and sensitively through its fluorescence spectrum to the presence of Cu²⁺. Job's plot gave a 2:1 stoichiometry of Probe-2/Cu²⁺ complex, which responds to the presence of S^2- and H₂PO₄^- in aqueous solution (ethanol/water = 1:2, borate buffer) by its absorption and fluorescence spectra. In addition, probe 2 mimics a digital comparator based on three INHIBIT logic gates by different outputs using HO^- and H⁺ as inputs. Moreover, probe 2 also executes AND and NOT TRANSFER logic gates using Cu²⁺ and S^2- as inputs.

Light and Cation-Driven Optical Switch based on a Stilbene-Appended Terpyridine System for the Design of Molecular-Scale Logic Devices

A molecular system comprising a terpyridine moiety capable of coordinating with different cations and a photoswitchable stilbene unit has been utilized here for the fabrication of multiply configurable logic systems. Incorporation of a substituted stilbene unit into the terpyridine motif generates an intraligand charge-transfer-sensitive module whose absorption and emission spectral properties are highly sensitive to light as well as cations. On the basis of the optical response profile of the receptor in the presence of selected cations as well as light of a specific wavelength, we are able to demonstrate multiple Boolean logic functions such as INHIBIT, IMPLICATION, OR, NOR, and NAND, as well as various combinations of them. Of particular interest, we utilized the present system for the construction of security keypad locks and memory devices by maintaining a proper sequence of the stimuli and monitoring either absorption or emission spectral response at a specific wavelength as the output signal. In addition to various Boolean logic functions, the present system has also the ability to mimic fuzzy logic operations for generating an infinite-valued logic scheme depending on its emission spectral responses upon varying the concentration of cationic (Fe²⁺ and/or Zn²⁺) and anionic (CN^-) inputs.

Three-Input Molecular Keypad Lock Based on a Norbornadiene-Quadricyclane Photoswitch

The photo- and acidochromic properties of a new generation norbornadiene derivative have been harnessed for the realization of a three-input keypad lock, where a specific sequence of inputs induces a unique output. Reversible quadricyclane/norbornadiene photoisomerization is reported, and this rare feature allows the first example of a norbornadiene-based molecular logic system. The function of this system is clearly rationalized in terms of the interconversion scheme and the absorption spectra of the involved species.

Synthesis of a single 1,8-naphthalimide fluorophore as a molecular logic lab for simultaneously detecting of Fe3+, Hg2+ and Cu2

A novel fluorescence sensing 1,8-naphthalimide fluorophore is synthesized and investigated. The novel probe comprising two different binding moieties is capable to detect selectively Fe³⁺ over the other representative metal ions as well as a combination of biologically important cations such as Fe³⁺, Cu²⁺ and Hg²⁺ in the physiological range without an interfering effect of the pHs. Due to the remarkable fluorescence changes in the presence of Fe³⁺, Hg²⁺ and Cu²⁺ ions, INH and AND logic gates are executed and the system is able to act as a single output combinatorial logic circuit with three chemical inputs.

Molecules for security measures: from keypad locks to advanced communication protocols

The idea of using molecules in the context of information security has sparked the interest of researchers from many scientific disciplines. This is clearly manifested in the diversity of the molecular platforms and the analytical techniques used for this purpose, some of which we highlight in this Tutorial Review. Moreover, those molecular systems can be used to emulate a broad spectrum of security measures. For a long time, molecular keypad locks enjoyed a clear preference and the review starts off with a description of how these devices developed. In the last few years, however, the field has evolved into something larger. Examples include more complex authentication protocols (multi-factor authentication and one-time passwords), the recognition of erroneous procedures in data transmission (parity devices), as well as steganographic and cryptographic protection.

A multi-responsive thiosemicarbazone-based probe for detection and discrimination of group 12 metal ions and its application in logic gates

A new simple 3-in-1 multi-response thiosemicarbazone-based chemosensor has been synthesized and characterized.

Perylene diimide-based organic π-motif for differentiating CN− and F− ions by electron-transfer and desilylation mechanisms: applications to complex logic circuits

PDI-SiHQ undergoes electron-transfer and desilylation reactions with CN⁻ and F⁻ ions to differentiate basic anions.

DNA-templated Ag nanoclusters as signal transducers for a label-free and resettable keypad lock

We present a unique, label-free and resettable molecular keypad lock that utilizes DNA-modulated Ag nanoclusters (Ag NCs) as signal responsers. The present work demonstrates the first example that exonuclease-catalyzed DNA hydrolysis reaction could be used to achieve the RESET function of a molecular keypad without complicated procedures.

An all-photonic molecule-based D flip-flop

The photochromic fluorescence switching of a fulgimide derivative was used to implement the first molecule-based D (delay) flip-flop device, which works based on the principles of sequential logic. The device operates exclusively with photonic signals and can be conveniently switched in repeated cycles.

An aptamer-based keypad lock system

An aptamer-based security system mimicking keypad lock function was successfully designed. The system was turned "ON" with a strong fluorescent output signal only when the inputs were added according to the correct combination and exact sequence. Otherwise, the system was kept "OFF" to prevent illegal access.

OFF-ON-OFF fluorescence switch with T-latch function

A novel molecular system with characteristics of an OFF-ON-OFF fluorescence switch was designed to integrate the function of a T-latch. In detail, a receptor(1)-fluorophore-receptor(2) architecture was adopted to achieve fluorescence switching upon addition of protons.