Keypad Lock Research Articles

Exploiting the Remote Server Access Support of CoAP Protocol

The constrained application protocol (CoAP) is a specially designed Web transfer protocol for use with constrained nodes and low-power networks. The widely available CoAP implementations have failed to validate the remote CoAP clients. Each CoAP client generates a random source port number when communicating with the CoAP server. However, we observe that in such implementations it is difficult to distinguish the regular packet and the malicious packet, opening a door for a potential off-path attack. The off-path attack is considered a weak attack on a constrained network and has received a less attention from the research community. However, the consequences resulting from such an attack cannot be ignored in practice. In this article, we exploit the combination of IP spoofing vulnerability and the remote server access support of CoAP is to be launch an off-path attack. The attacker injects a fake request message to change the credentials of the 6LoWPAN smart door keypad lock system. This creates a request spoofing vulnerability in CoAP, and the attacker exploits this vulnerability to gain full access to the system. Through our implementation, we demonstrated the feasibility of the attack scenario on the 6LoWPAN-CoAP network using smart door keypad lock. We proposed a machine learning (ML)-based approach to mitigate such attacks. To the best of our knowledge, we believe that this is the first article to analyze the remote CoAP server access support and request spoofing vulnerability of CoAP to launch an off-path attack and demonstrate how an ML-based approach can be deployed to prevent such attacks.

Dual macro-cyclic component based logic diversity

In continuation of our recent studies on the photophysics of a photodynamic therapeutic agent, harmine (HM) in model membrane, the present contribution highlights a new model to design multiple logic circuits, a memory device and a molecular lock regulated by dual macrocyclic components as chemical inputs. The unique reversible photoswitching regulated by macrocyclic components plays decisive role in the manifestation of the final outputs for the logic functions. Inspired by this phenomenon, herein, we are reporting the use of a photosensitizer molecule for designing of various logic circuits at molecular level with the intention to escalate the next generation molecular logic arena. For these desired outsets, fluorescence spectroscopic changes of HM upon addition of macrocyclic components (CTAB and β-CD) were utilised. Beyond the simple single input single output logic gates (NOT, YES, PASS 0 and PASS 1), we were also able to design IMPLICATION and INHIBIT gates. In addition to different logic functions, the modulations of the optical responses of HM driven by the macrocyclic components were employed to design “Erase-Read-Write-Read” and “Write-Read-Erase-Read” type memory units. Moreover, considering the optical responses of HM we proposed a supramolecular keypad lock operated through unique sequential entry of opto-chemical passwords.

Bismuth triggered selective colorimetric naked-eye detection for oxalate ions based on bromopyrogallol red that works as a molecular keypad lock

ABSTRACT A novel colorimetric probe based on the bromopyrogallol red (BPR) for the sequential detection of Bi3+ and C2O4 2− was designed. The presence of Bi3+ led to a distinct naked-eye colour change in DMSO/H2O (1:3, v/v) media. The detection limit of BPR for Bi3+ was down to nanomolar concentration (1.17 nmol L−1). Also, the sensing ability of BPR for Bi3+ was successfully carried out in bismuth tablet and urine sample. Moreover, the resulting BPR-Bi3+ complex acted as an efficient colorimetric chemosensor for C2O4 2− via a colour change. Therefore, chemosensor BPR-Bi3+ can illustrate the ability to determine C2O4 2- up to 0.15 µmol L−1, selectively. Notably, the absorbance changes of BPR upon the addition of Bi3+ and C2O4 2− were utilised as AND and NAND logic gates operating at the molecular level with Bi3+and C2O4 2− as chemical inputs and the absorbance signal as the output. The chemical inputs of Bi3+ and C2O4 2- in a sequential system produce an output which mimics the operation of a security keypad lock. This study provides a practical application for the sensing of C2O4 2− ions in vegetable and urine samples by the construction of the supramolecular system.

A developed chromogenic probe for determination of dual analyte with logic gates function and keypad-lock

ABSTRACT In the current study, a novel and facile selective colorimetric approach was developed by Eriochrome Black T (EBT) for naked-eye detection and determination of nickel (Ni2+) and cyanide (CN−) ions in H2O/DMSO (9:1, v/v) media. The chemosensing behaviour of EBT has been indicated through UV-Vis absorbance spectra, visual colour changes, and FTIR spectra. First, EBT could selectively identify Ni2+ over other competitive cation in 90% aqueous media and then, the resulting EBT-Ni2+complex was successfully applied for selective colorimetric recognition of CN− based on azo-hydrazone tautomeric skeletons. The detection limit of EBT towards Ni2+ and CN− were calculated to be 0.06 µmol L−1 and 0.15 µmol L−1, respectively. These consequences represent an innovative type of nimble chemosensor for manifold target ions using simple colorimetric and sequential detection. When operated by chemical ions Ni2+ and CN− can act as an absorbance switch, distinguishing a multi-addressable system. In addition, INVERTER (INV) and INHIBIT (INH) logic gates at different wavelengths and a keypad lock were created by applying chemical ions Ni2+ and CN− as two inputs and an absorption mode at 541 nm as an output on the basis of suitable chemical stimuli.

Nitrogen-Doped Graphene Oxide Dots-Based "Turn-OFF" H2O2, Au(III), and "Turn-OFF-ON" Hg(II) Sensors as Logic Gates and Molecular Keypad Locks.

Fluorescent nitrogen-doped graphene oxide dots (NGODs) have been demonstrated as an on–off nanosensor for the detection of Hg2+, Au3+, and H2O2. As compared to l-cystine, where the luminescence signal recovery results from the detachment of Hg2+ from the NGODs, signal recovery through l-ascorbic acid (turn-off–on model) has been attributed to the reduction of Hg2+ to Hg0. The sustainable recovery of the photoluminescence signal is demonstrated using common citrus fruits containing vitamin C (l-AA), suggesting a promising practical usage of this sensing system. Additionally, the sensitivity of NGOD- and AA-originated signal recovery from the Hg(II)–NGODs mixture has been successfully tested in Hg2+ ion-spiked tap water from three different places. Mimic devices were executed and verified on the basis of characteristic spectral changes, and the possible utility of this system in electronic security and memory element devices has also been demonstrated. Considering an easy synthesis process and excellent performance of NGODs, this investigation opens up new opportunities for preparing high-quality fluorescent NGODs to meet the requirements of many applications.

A smart FRET probe exhibiting a molecular keypad lock device based on rapid detection of nitric oxide mediated by Cu2+ ion

A rhodamine-dansyl conjugate (RPD) has been synthesized for rapid FRET-based ratiometric detection of nitric oxide (NO) up to nM level mediated by the Cu2+ ions. The emission band of dansyl centered at 481 nm showed quenching upon addition of Cu2+ and further addition of NO, showed a decrease at dansyl emission band and ratiometrically generate a new band at 580 nm corresponding to the open spirolactam derivative of rhodamine. Subsequent chemical inputs of Cu2+ and NO generate a smart molecular level security device with a unique set of inputs to unlock the device. The rapid detection of NO is devoid of false signalling, as the detection is dependent on sequence-based two input correct combination. The [RPD-Cu2+] solution was also highly efficient to detect NO in solution by a visual change in colour: i.e. colourless to pink and pale green to orange under naked eye and UV-light respectively. The probe-Cu2+ solution exhibits excellent NO imaging in HeLa cells with low cytotoxicity and the lower level of emission in the presence of probe-Cu2+ which is advantageous to see the initial incubation of probe inside the live cells. The applicability of [RPD+Cu2+] has been proven by efficient detection of NO in HeLa cells by dual enhanced emissions in green/red channels.

A reversible fluorescence “ON–OFF–ON” sensor for sequential detection of F− and Cu2+ ions and its application as a molecular-scale logic device and security keypad lock

A new azoimine receptor, R1, was synthesized by Schiff base condensation of 4-(4-butylphenyl) azophenol and 2,6-diaminopyridine and acts as a colorimetric and fluorometric chemosensor for F− and also toward Cu2+ ions in aqueous environment. UV–Vis absorption and fluorescent emission spectra were employed to study the sensing process. Emission study was performed to examine the dual sensing ability of the obtained probe with sequential addition of F− followed by Cu2+ and vice versa. The receptor is an efficient “ON–OFF” fluorescent probe for the fluoride ion. Also, R1 + F− operated as an “OFF–ON” fluorescent sensor for Cu2+ ions. Considering emission intensity and absorption wavelength for F− and Cu2+ ions, a molecular system was developed with the ability to mimic the functions of XNOR logic gating on the molecular level. In addition, R1 behaved as a molecular security keypad lock with F− and Cu2+ inputs. The keypad lock operation is particularly important, as the output of the system depends not only on the proper combination but also on the order of input signals, creating the correct password that can be used to “open” this molecular keypad lock through strong fluorescence emission at 460 nm.

Synthesis of methionine methyl ester-modified coumarin as the fluorescent-colorimetric chemosensor for selective detection Cu2+ with application in molecular logic gate.

A methionine methyl ester-modified coumarin derivative was designed and synthesized, which could discriminate Cu2+ from other metal ions in HEPES buffer (10 mM, pH 7.4)/CH3CN (40:60, V/V). The detection limit of WM toward Cu2+ was 1.84 × 10-7 M, which was lower than the concentration of Cu2+ in drinking water suggested by WHO and EPA. And the proposed coordination mode exhibiting the interaction between WM and Cu2+ was studied by UV-Vis, fluorescence spectrum, ESI-MS and FT-IR. Based on the fluorescent reversibility of WM, WM was considered as a molecular logic gate and molecular keypad lock. In addition, the test strips and the silica gel plates prepared from the solution of WM also demonstrate the favorable selectivity toward Cu2+.

Retraction: A simple rhodamine-based dual signalling reversible molecular switch for recognition of Al(iii) with promising applications for advanced logic operations – ‘OR’, ‘Keypad Lock’ & ‘INHIBIT’ logic function and cell-imaging studies

Retraction of ‘A simple rhodamine-based dual signalling reversible molecular switch for recognition of Al(iii) with promising applications for advanced logic operations – ‘OR’, ‘Keypad Lock’ & ‘INHIBIT’ logic function and cell-imaging studies’ by Tarun Mistri et al., Analyst, 2014, DOI: 10.1039/C3AN02255B.

Succinic acid-assisted stability enhancement of a colloidal organometal halide perovskite and its application as a fluorescent keypad lock

MAPbBr3 perovskite nanocrystals were synthesized using bidentate succinic acid as a capping ligand for stable fluorescence.

Antibiotic-triggered reversible luminescence switching in amine-grafted mixed-linker MOF: exceptional turn-on and ultrafast nanomolar detection of sulfadiazine and adenosine monophosphate with molecular keypad lock functionality

Mixed-linker CSMCRI-2 demonstrates the turn-on and nanomolar detection of antibiotics and biophosphates with antibiotic-triggered reversible fluorescence switching and keypad lock function.

An efficient “Ratiometric” fluorescent chemosensor for the selective detection of Hg2+ ions based on phosphonates: its live cell imaging and molecular keypad lock applications

Herein, we have reported the ability of smart chemosensors (L1 and L2) to selectively detect Hg(ii) ions over other metal ions and examined this phenomenon by various spectroscopy techniques.

Development of three ways molecular logic gate based on water soluble phenazine fluorescent 'selective ion' sensor.

New hydrophilic fluorescent selective ion sensor based on phenazine and phthalazine moieties, 1,1'-(phenazine-2,3-diyl)-bis(3-(1,4-dihydroxyphthalazin-6-yl)urea) (1), has been designed, synthesized and characterized. Interestingly, sensor 1 exhibits prominent "turn-on" and "turn-off" fluorogenic signaling at 580 nm towards Fe2+ & AcO- and Sr2+ & Cu2+, respectively. The fluorescence titration experiments shed light on the nature of the interaction between 1 and guest molecules (Fe2+, Sr2+, Cu2+ and AcO-), which divulge that 1 is flexible enough to orient itself according to the size of the guest molecule. Water mediated excited-state intramolecular proton transfer (ESIPT) and photo-induced electron transfer (PET) mechanisms are responsible for the dual behavior of 1, which binds with guest molecules in 1:1 stoichiometry. Based on the significant duplex fluorescence response of 1, a molecular logic gate keypad lock with sixteen "on" passwords for a storage system has been developed.

Sequential displacement strategy for selective and highly sensitive detection of Zn2+, Hg2+ and S2- ions: An approach toward a molecular keypad lock.

A thiocarbonohydrazone locked salicylidene based macrocycle ligand L has been synthesized and its ion sensing properties were examined by UV-visible and fluorescence spectroscopy. The macrocycle serves as a highly selective colorimetric sensor for Hg2+ ions while it acts as an excellent fluorescent sensor for Zn2+ ions by exhibiting a green fluorescence at 498 nm even in the presence of interfering ions. A detailed analysis of binding characteristics such as complex stoichiometry, association constant and detection limits of L toward Hg2+ and Zn2+ ions were evaluated by UV-visible and fluorescence experiments which revealed a stronger binding affinity and higher detection limit of L toward the mercury ions. Further, the sequential displacement strategy for the chromofluorogenic detection of Zn2+, Hg2+ and S2- ions by ligand L, has been studied comprehensively. Finally, the ion-responsive fluorescence output signal of L were employed to design a molecular keypad lock which could be accessible by two users having two different set of chemical passwords (inputs) through distinguishable optical trajectories.

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.

Pineapple Peel-Derived Carbon Dots: Applications as Sensor, Molecular Keypad Lock, and Memory Device.

Herein, the fluorescent carbon dots (CDs) with blue emission were prepared by hydrothermal treatment using pineapple peel as a source of carbon. The as-prepared CDs exhibited turn-Off fluorescence behavior toward Hg2+ and subsequent turn-On behavior for l-cysteine along with enhanced biocompatibility and negligible cytotoxicity for cell imaging. The practical applicability of carbon dots was used for the quantification of Hg2+ in water. On the basis of the spectral characteristic changes, we have designed individual elementary logic operations such as NOT and IMP gates, by utilizing CD as probe and Hg2+ and l-Cys as chemical inputs. We have also demonstrated the utility of this system in electronic security devices and as memory element, with the idea of the switching.

DNA Probes for Implementation of Multiple Molecular Computations Using a Lateral Flow Strip Biosensor as the Sensing Platform.

A series of advanced logic circuits have been successfully constructed to perform multiple arithmetic functions using a lateral flow strip biosensor as the sensing platform, including half adder, half subtractor, multiplexer, demultiplexer, and keypad lock. In each circuit computing, the computing elements are the DNA probes, which can implement the DNA assembly process to generate the output single-stranded nucleic acid. The strip biosensor is used as the sensing platform to distinguish the output of the logic gates. The distinctive advantage of our proposed biocomputing system is that the logic events can be transformed into the red bands on the test zones, which can be observed by the naked eye. The logic system with convenient operation, rapid response, and cost-effectiveness features will facilitate the portable analysis at ambient temperature without resorting to any instrumentation. The versatility and power of the logic computation demonstrated here indicate its great potential in intelligent point-of-care (POC) disease diagnosis and on-site environmental monitoring.

An enzymatic calculation system based on electrochemiluminescence and fluorescence of luminol and cyclic voltammetry of ferrocene methanol

In this work, a biomolecular calculation system was developed based on electrochemiluminescence (ECL) and fluorescence emission (FL) of luminol and cyclic voltammetry (CV) of ferrocene methanol (FMA). When triethylamine (TEA) was added in luminol solution as a coreactant, a great ECL peak at 1.1 V was observed. While the further addition of enzymatic system, esterase/ethyl butyrate (EB), would significantly lower the ECL response. On the other hand, TEA could quench the FL signal of luminol at 430 nm, while the injection of esterase/EB in the luminol solution could enhance the FL signal. Furthermore, FMA exhibited a CV peak pair at 0.2 V and could decrease the ECL signal greatly in the luminol/TEA solution. Based on these interesting results, a 3-input and 5-output biomolecular logic gate was established with TEA, FMA and esterase/EB as inputs and the ECL, CV and FL signals as outputs. Moreover, some nonarithmetic logic devices, such as an encoder, a decoder, a 3-input keypad lock and two dual transfer gates were elaborately designed on the same platform. This work presented a new example of how the complexity of biocomputing system could be enhanced either by increasing the number of outputs of traditional logic gates or by fabricating some nonarithmetic logic devices based on the same simple electrochemical system.

Multifunctional Logic Applications of a Single Molecule: A Molecular Photo‐Switch Performing as Simple and Complex Gates, Memory Element, and a Molecular Keypad Lock

AbstractCarbazole (CZ) can act as a photo‐switch leading to a multifunctional logic system when triggered by fluoride (F–) ions, H2O and light, through efficient interaction of the pyrrole unit with the anions. Here we are reporting a unimolecular platform of CZ (and case specific CZ‐F–) that can be configured as NOT, YES, complimentary IMPLICATION and INHIBIT, a new complex logic gate performing IF‐THEN and NOT operations and a memory element with cyclic “Erase‐Read‐Write‐Read” ability with feedback loop mechanism. The fluorescence responses of the CZ system also have been exploited to design a potential highly secured molecular keypad lock operating with a purely opto‐chemical password composed with optical and chemical input keys. The system displays the applications of light responsive molecules as multifunctional, reconfigurable molecular logic devices that may lead towards true molecular information processing units.

A chemical/molecular 4-input/2-output keypad lock with easy resettability based on red-emission carbon dots-Prussian blue composite film electrodes.

In this work, a resettable 4-input/2-output keypad lock system based on red-emission carbon dots (rCDs) and Prussian blue (PB) modified electrodes was developed. Electrochromic PB layers were first electrochemically deposited on the indium tin oxide (ITO) electrode surface. An admixture of rCDs and chitosan (Chi) was then cast on the surface of PB layers, forming rCDs-Chi/PB film electrodes. UV-vis absorption of the films was sensitive to the applied potential since the blue PB constituent of the films would be transformed to nearly colorless Prussian white (PW) at the reduction potential of -0.2 V and then from PW back to PB at the oxidation potential of 0.4 V, and the transformation between PB and PW would also influence the fluorescence emission of the rCD constituent in the films. The addition of cysteine (Cys) in the testing solution could reduce the PB in the films into PW and generate an amperometric electrocatalytic current at 0.4 V. Meanwhile, the addition of Fe3+ in solution could greatly quench the fluorescence from the rCD component in the films. Thus, the responses of UV-vis absorbance, fluorescence emission and amperometric current of the rCDs-Chi/PB film electrode system exhibited potential-, Cys- and Fe3+-responsive switching properties. Based on the aforementioned work, a combinational logic gate circuit with 3 inputs and 3 outputs was established. In particular, on the same platform, a novel chemical/molecular 4-input/2-output keypad lock with easy resettability was elaborately designed with amperometric current and fluorescence peak intensity as two different types of outputs, so that a higher security level could be achieved.