Invisible Security Ink Based on Water‐Soluble Graphitic Carbon Nitride Quantum Dots

Stimuli‐responsive photoluminescent (PL) materials have been widely used as fluorescent ink for data security applications. However, traditional fluorescent inks are limited in maintaining the secrecy of information because the inks are usually visible by naked eyes either under ambient light or UV‐light illumination. Here, we introduced metal‐free water‐soluble graphitic carbon nitride quantum dots (g‐CNQDs) as invisible security ink for information coding, encryption, and decryption. The information written by the g‐CNQDs is invisible in ambient light and UV light, but it can be readable by a fluorescence microplate reader. Moreover, the information can be encrypted and decrypted by using oxalic acid and sodium bicarbonate as encryption reagent and decryption reagent, respectively. Our findings provide new opportunities for high‐level information coding and protection by using water‐soluble g‐CNQDs as invisible security ink.     

Excitation-wavelength-dependent fluorescent organohydrogel for dynamic information anti-counterfeiting

Anti-counterfeiting labels with various fluorescent colors are of great importance in information encryption-decryption, but are still limited to static information display. Therefore, it is urgent to develop new materials and encryption-decryption logic for improving the security level of secret information. In this study, an organohydrogel made up of poly(N,N-dimethylacrylamide) (pDMA) hydrogel network and polyoctadecyl methacrylate (pSMA) organogel network that copolymerized with two fluorophores, 6-acrylamidopicolinic acid moieties (6APA, fluorescent ligand) and spiropyran units (SPMA, photochromic monomer), was prepared by a two-step interpenetrating method. As UV light of 365 nm and 254 nm can both cleave C_spiro-O bonds of SPMA, and the green fluorescence of 6APA-Tb³⁺ can only be excited by 254 nm light, the organohydrogel displays yellow and red under the irradiation of 254 nm and 365 nm, respectively. In addition to wavelength selectivity, these two fluorophores are thermal-responsive, leading to the fluorescence variation of the organohydrogel during heating process. As a result, secret information loaded on the organohydrogel can be decrypted by the irradiation of UV light, and the authenticity of the information can be further identified by thermal stimulation. Our fluorescent organohydrogel can act as an effective anti-counterfeiting label to improve the information security and protect the information from being cracked.     

Stimuli‐Responsive Naphthalene Diimide as Invisible Ink: A Rewritable Fluorescent Platform for Anti‐Counterfeiting

Herein, we report an approach to combat counterfeiting and storage of valuable information based on the solid‐state fluorescence switching behavior of isoniazid functionalized naphthalene diimide (ISO_NDI) in response to an external stimuli (i. e., HCl vapor). The unique feature of ISO_NDI is further utilized to develop an invisible ink (ISO_NDI‐PVA) with commercial polymer polyvinyl alcohol (PVA). A solid‐state fluorescence recovery was observed while loading with HCl vapors. This exclusive property of the material could be applied directly as a security ink for confidential data storage purpose. Based on above strategy, we successfully realized the rewritable application by using ISO_NDI‐PVA ink and confirm its practical efficacy on various substrates by creating different patterns. The solid‐state fluorescence switching behavior of ISO_NDI‐PVA ink exhibited reversible on/off signal for multiple cycles under the influence of HCl/NH₃ vapors. Mechanistic investigation supports a clear participation of intermolecular charge transfer (ICT) phenomenon in the solid‐state fluorescence switching property. The ease of fabricating the ink with invisible to visible characteristics in response to HCl vapors provides new opportunities for exploring the application of ISO_NDI‐PVA as invisible ink for targeted security applications.     

Loading Photochromic Molecules into a Luminescent Metal–Organic Framework for Information Anticounterfeiting

Stimuli‐responsive photoluminescent materials have attracted considerable attention owing to their potential applications in security protection because the information recorded directly in materials with static luminescent outputs are usually visible under either ambient or UV light. Herein, we realize reversible information anticounterfeiting by loading a photoswitchable diarylethene derivative into a lanthanide metal–organic framework (MOF). Light triggers the open‐ and closed‐form isomerization of the diarylethene unit, which respectively regulates the inactivation and activation of the photochromic FRET process between the diarylethene acceptor and lanthanide donor, resulting in reversible luminescence on–off switching of the lanthanide emitting center in the MOF host. This photoresponsive host–guest system allows for reversible multiple information pattern visible/invisible transformation by simply alternating the exposure to UV and visible light.     

Orthogonal signal correction applied to the classification of wine and molasses vinegar samples by near-infrared spectroscopy. Feasibility study for the detection and quantification of adulterated vinegar samples

The most common fraudulent practice in the vinegar industry is the addition of alcohol of different origins to the base wine used to produce wine vinegar with the objective of reducing manufacturing costs. The mixture is then sold commercially as genuine wine vinegar, thus constituting a fraud to consumers and an unfair practice with respect to the rest of the vinegar sector. A method based on near-infrared spectroscopy has been developed to discriminate between white wine vinegar and alcohol or molasses vinegar. Orthogonal signal correction (OSC) was applied to a set of 96 vinegar NIR spectra from both original and artificial blends made in the laboratory, to remove information unrelated to a specific response. The specific response used to correct the spectra was the extent of adulteration of the vinegar samples. Both raw and corrected NIR spectra were used to develop separate classification models using the potential functions method as a class-modeling technique. The previous models were compared to evaluate the suitability of near-infrared spectroscopy as a rapid method for discrimination between vinegar origin. The transformation of vinegar NIR spectra by means of an orthogonal signal-correction method resulted in notable improvement of the specificity of the constructed classification models. The same orthogonal correction approach was also used to perform a calibration model able to detect and quantify the amount of exogenous alcohol added to the commercial product. This regression model can be used to quantify the extent of adulteration of new vinegar samples.     

Tuning 2D Light Upconversion Emission by Modulating Phonon Relaxation

The photonic upconversion in rare earth atoms is widely used to convert “invisible” near infrared photons to “visible” photons with continuous wave light. By using a patterned substrate, upconversion become a route for creating new information‐incorporating security codes. The amount of information in the cipher increases in proportion to the number of emission colors as well as the pattern structure. Subsequently, changing the chemical composition of upconversion phosphors on 2 D substrates is required to manufacture information‐rich upconversion cryptography. In this study, we exploited temperature‐controlled thermal reaction on upconversion films deposited on a quartz substrate to prepare security information codes. Multiple color emission was generated from upconversion films as the result of inserting high‐frequency molecular oscillators into the film structures. Fourier‐transform infrared (FTIR) and time‐resolved study corroborated the mechanism of spectral variation of upconversion films.     

A Dual-Responsive Liquid Crystal Elastomer for Multi-Level Encryption and Transient Information Display

Information security has gained increasing attention in the past decade, leading to the development of advanced materials for anti-counterfeiting, encryption and instantaneous information display. However, it remains challenging to achieve high information security with simple encryption procedures and low-energy stimuli. Herein, a series of strain/temperature-responsive liquid crystal elastomers (LCEs) are developed to achieve dual-modal, multi-level information encryption and real-time, rewritable transient information display. The as-prepared polydomain LCEs can change from an opaque state to a transparent state under strain or temperature stimuli, with the transition strains or temperatures highly dependent on the concentration of long-chain flexible spacers. Information encrypted by different LCE inks can be decrypted under specific strains or temperatures, leading to multi-level protection of information security. Furthermore, with the combination of the phase transition of polydomain LCEs and the photothermal effect of multi-walled carbon nanotubes (MWCNTs), we achieved a repeatable transient information display by using near-infrared (NIR) light as a pen for writing. This study provides new insight into the development of advanced encryption materials with versatility and high security for broad applications.     

Photo-modulated wide-spectrum chromism in Eu3+ and Eu3+/Tb3+ photochromic coordination polymer gels: application in decoding secret information

Photo-switching emission of photochromic materials has paramount importance in the field of optoelectronics. Here, we report synthesis and characterization of a dithienylethene (DTE) based photochromic low molecular weight gelator (LMWG) and self-assembly with lanthanide (Eu³⁺ and Tb³⁺) ions to form a photochromic coordination polymer gel (pcCPG). Based on DTE ring opening and closing, the TPY-DTE gel shuttles from pale-yellow coloured TPY-DTE-O to dark blue coloured TPY-DTE-C and vice versa upon irradiating with UV and visible light, respectively, and both the photoisomers show distinct optical properties. Furthermore, integration of Eu³⁺ and Tb³⁺ lanthanides with TPY-DTE resulted in red and green emissive Eu-pcCPG (Q.Y. = 18.7% for the open state) and Tb-pcCPG (Q.Y. = 23.4% for the open state), respectively. The photoisomers of Eu-pcCPG exhibit photo-switchable spherical to fibrous reversible morphology transformation. Importantly, an excellent spectral overlap of the Eu³⁺ centred emission and absorption of DTE in the closed form offered photo-switchable emission properties in Eu-pcCPG based on pcFRET (energy transfer efficiency >94%). Further, owing to the high processability and photo-switchable emission, the Eu-pcCPG has been utilized as invisible security ink for protecting confidential information. Interestingly, mixed Eu³⁺/Tb³⁺ pcCPG exhibited photo-modulated multi-spectrum chromism reversibly where the colour changes from yellow, blue, and red to green and vice versa under suitable light irradiation.

A lanthanide based photochromic coordination polymer gel (pcCPG) material has been developed which showed photomodulated colour change based on pcFRET and has the potential to be employed for decoding secret information.     

Optical storage of hidden images in ultraviolet-cured polymer dispersed liquid crystals

Among the different methods used to prepare polymer dispersed liquid crystals (PDLCs), polymerization induced phase separation can be successfully exploited to obtain optical recording of high resolution holographic gratings and binary images in these materials. In this paper we report a new method that allows hidden images to be obtained in PDLCs that are not detectable by light in the visible range. The possibility of storing invisible images during the curing process will be described and discussed. The binary images obtained can be detected by illuminating them with low power UV radiation, thus opening the way to interesting applications in the field of optical storage of reserved information.     

Optical storage of hidden images in ultraviolet-cured polymer dispersed liquid crystals

Among the different methods used to prepare polymer dispersed liquid crystals (PDLCs), polymerization induced phase separation can be successfully exploited to obtain optical recording of high resolution holographic gratings and binary images in these materials. In this paper we report a new method that allows hidden images to be obtained in PDLCs that are not detectable by light in the visible range. The possibility of storing invisible images during the curing process will be described and discussed. The binary images obtained can be detected by illuminating them with low power UV radiation, thus opening the way to interesting applications in the field of optical storage of reserved information.     

Butyltin compounds in vinegar collected in Beijing: Species distribution and source investigation

Forty-eight vinegar samples including white vinegar,rice vinegar and mature vinegar were collected from several markets in Beijing.Butyltin compounds were determined by headspace solid-phase microextraction coupled with gas chromatography and flame photometric detector after in situ ethylation with sodium tetraethylborate.Butyltin species were detected in sixteen vinegar samples and ranged from 0.012 to 14.10 μg Sn L 1.The detection rate of white vinegar is higher than that of rice vinegar and mature vinegar.Vinegar samples with relatively high butyltin concentration(>1.5 μg Sn L 1) were those stored in plastic bags,indicating that the plastic bag was one of the possible sources of butyltin contamination.This was further confirmed by the leaching experiments of three selected plastic bags,and monobutyltin was detected in the leaching solvents.According to the estimation,the average daily intake of total butyltin compounds through vinegar consumption is about 0.04 ng Sn/kg b.w.,much lower than the Tolerable Daily Intake(TDI) of 100 ng Sn/kg b.w.set by the European Food Safety Authority(EFSA).     

13C-Isotope ratio mass spectrometry as a potential tool for the forensic analysis of white architectural paint: a preliminary study

Paints have a dual role in society, to protect materials from environmental agents such as ultraviolet light, moisture and oxygen, and to make painted materials look more attractive. Variability in paint samples is often due to binder and pigment type within the sample. The most common resin used in decorative paints is drying oil alkyd resin, which incorporates soybean oil and vinyl acrylic based latexes. Traditional analytical methods used by forensic scientists may be able to say whether two paint samples are indistinguishable but cannot conclusively say that they both originate from the same source. To find out if isotopic composition can provide an added dimension of information, 28 different white architectural paints were analysed for (13)C abundance using isotope ratio mass spectrometry. In addition, variations in application, drying time and thickness were also investigated to assess the discriminatory power of (13)C data from white paints with an unknown history. Preliminary results indicate that this method could aid screening of paint samples.     

The Fire/Heat Concept and Its Journey from Prehistoric Time into the Third Millennium

The notion of fire/light/heat/energy is recognized as an integrating element in the pathway of ordering matter and society, and its historical aspects are thoroughly reviewed. Fire is argued to be a philosophical archetype and its role in the early concept of four elements is discussed. The Indian, Arabic and Greek historical bases are mentioned. Alchemy is briefly reviewed as a source of the wider adoption of fire. The era of renaissance and the new age are also included. The message of fire/heat is nowadays focused on the progress of civilization, with the assumption of engines as information transducers based on the conscious exploitation of fire. The role of chaos is emphasized. Overall, a condensed but consistent view is given of the various concepts that emerged during the historical progress of the understanding of heat (noting 61 references). This revised version was published online in July 2006 with corrections to the Cover Date.     

Blue-to-green manipulation of carbon dots from fluorescence to ultralong room-temperature phosphorescence for high-level anti-counterfeiting

Carbon dots (CDs) with fluorescence (FL) and room-temperature phosphorescence (RTP) optical properties have attracted dramatically growing interest in anti-counterfeiting application. Herein, color-tunable and stable FL and ultralong RTP (to naked eyes ~14 s) are successfully achieved in CDs system. Encoding information and patterns fabricated by directly screen-printing method are invisible to eyes under natural light. Interestingly, clear and multicolor patterns with tunable FL and RTP emissions are identified under the 365 nm, 395 nm and 465 nm excitation and removal of them, indicating potential application of carbon dots with different FL and RTP outputs in the high-level photonic anti-counterfeiting field.     

New Phosphors for White LEDs

White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or UV LEDs) and photoluminescence phosphors. GaN-based highly efficient blue InGaN LEDs combined with phosphors can produce white light. These solid-state LED lamps have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability, and long operating lifetime (about 100,000 hours). For the purpose of development of high energy-efficient white light sources, we need to produce highly efficient new phosphors, which can absorb excitation energy from blue or UV LEDs and generate emissions.In this paper, we investigate the development of blue or UV LEDs by the appropriate combination of new phosphors which can lead us to obtain high brightness white light. The criteria of choosing the best phosphors, for blue (380-450 nm) and UV (360-400 nm) LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance light between the light emission from blue LEDs and the yellow YAG:Ce,Gd phosphor is important to obtain white light with high color temperature. The phosphors with high efficiency which can be excited by UV LEDs are important to obtain the white light with high color rendering index.     

Advantaging Synergy Photocatalysis with Graphene‐Related Carbon as a Counterpart Player of Titania

The enhancement of photocatalytic activity of TiO₂ can be made either by promoting absorption efficiency of photon energy or by reducing recombination losses of photogenerated charge carriers, for which fabrication of nanocomposite structure with carbon materials is an optional selection. Among various nanocarbons, graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO) are more favorable as the counterpart materials because they can provide availability of both obverse and reverse surface, thus doubling effective sites for adsorption, loading of nanoparticles, and interfacial interaction with the loaded nanoparticles. Composition of G/GO with titania, therefore, is a hopeful strategy for achieving synergy or cooperative effect in photocatalysis. In this personal account, we focus on the background and methodology of several soft chemical approaches that we have utilized up to date to fabricate nanocomposites of G/GO and titania, aiming to shed light on the importance of designing of nanocomposite structure for enhancing photocatalysis. In addition, we emphasize the role of interfacial interaction between carbon and titania by exemplifying a hybridized photocatalyst based on inexpensive biomass‐derived carbon sphere (CS), and demonstrate that it is a crucial influential factor underlying an enhanced visible light photocatalysis. CS can be a better selection as a counterpart component than G/GO, whose core‐shell composing structure with titania (TiO₂@CS) can efficiently induce charge transfer so as to achieve a much higher photocatalytic performance under visible light illumination as compared to the composite of rGO and titania.     

Phthalocyanine thio-pyridinium derivatives as antibacterial photosensitizers

This study describes the synthesis of three new tetra- and octa-thio-pyridinium phthalocyanine derivatives. PSs 3a and 4a were prepared from the tetramerization of phthalonitriles 1 and 2, respectively, whereas PS 5 was prepared from the nucleophilic substitution of the 8 beta fluor atoms of hexadecafluorophthalocyaninatozinc(II) by mercaptopyridine, followed by cationization. The recombinant bioluminescent Escherichia coli strain was used to assess, in real time, the photoinactivation efficiency of these cationic phthalocyanines, under white and red light. The cellular localization and uptake were also determined to assess the potential of the new phthalocyanines as antibacterial agents. Derivative 3a was the most effective PS, causing a 5 logs reduction in bioluminescence after 30 min of irradiation under white or red lights. The photoinactivation efficiency of the phthalocyanine 4a was similar (5 logs reduction in bioluminescence) to that of 3a when irradiated with white light, but the efficiency of inactivation was reduced (2.1 logs reduction in bioluminescence) under red light. The tetra-substituted phthalocyanine 3a also generates high amounts of singlet oxygen, does not aggregate in PBS and is highly fluorescent, which makes it an effective PS and a promising fluorescent labeling.     

Stimulatory effect of red light on starch accumulation in a marine green alga,chlamydomonas sp. strain MGA161

A marine green alga,Chlamydomonas sp. strain MGA161 was cultivated under illumination of red and white lights. The growth rate under red light illumination was almost the same as that in the basic conditions under white light illumination, but red light-grown cells accumulated almost twice as much starch as white light-grown cells. Although there was a slight decrease in carbonic anhydrase activity, red light-illuminated cells had almost 2.3 times the fructose-l,6-diphos-phatase activity of white light-illuminated cells. Red light might stimulate starch accumulation by increasing the amounts of enzymes related to carbon fixation through the phytochrome system. Cells grown under red light degraded 1.6 times as much starch and produced 1.7 times as much hydrogen and 1.6 times as much ethanol compared with cells grown under white light during 12 h of dark anaerobic fermentation.     

Application of vibrational spectroscopy techniques for material identification from fire debris

The primary goal of this research is to demonstrate the use of vibrational spectroscopy techniques as a tool for the identification of materials post fire. This paper discusses the use micro-Raman spectroscopy and ATR-FTIR to identify materials found in fire debris. The polymeric materials under study were high density and low density polyethylene (HDPE and LDPE), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA) and cotton. These are commonly materials found in households around the world, their identification from the debris provides useful forensic information on the spatial distribution of fuels in a fire compartment, thus allowing for accurate analysis and modelling. Earlier work has established Raman spectroscopy to be a very good tool for material identification post fire. The addition of ATR-FTIR spectroscopy as a technique in developing this novel tool for identification of materials post fire has established vibrational spectroscopy in the area of fire investigation. This study indicated that the limitations associated with Raman spectroscopy in post fire identification, could be made insignificant by the strengths of ATR-FTIR spectroscopy and vice versa. To further establish the validity of this identification process principal component analysis was used to discriminate between the spectrum of the burnt materials and an error analysis computed. Both techniques demonstrated that identification could be done with very minimal confusion between the materials studied.     

轻工业纤维素生物质过程残渣能源化技术

以农产品为原料的轻工业大都是典型的流程工业,在通过转化过程将原料转化为食品、饮料、添加剂、调味料、纸和中成药等产品的同时产生被称为过程残渣的固体废物与废料,如白酒糟、酒精糟、醋糟、甘蔗渣、中药渣、油粕、酱渣、菌渣和造纸黑液可熔渣等.这些残渣产生于特定的生产过程,富含纤维素、蛋白质或木质素,因此代表一种已经被集中的生物质资源.它们同时含水50%-80%、易腐烂变质、甚至呈弱酸碱性,因此是重要的环境污染源.本文着眼于轻工生物质过程残渣的高值化利用,分析指出富含纤维素的白酒糟、醋糟、甘蔗渣、中药渣、茶渣和造纸边角料等适合作为生物质能源而被转化利用,并根据资源特征提出了可能的技术路线.通过分别对热化学路线涉及的脱水干燥、燃烧发电与气化发电技术和集成乙醇发酵、沼气发酵的复合转化技术进行技术综述,最后针对不同规模的富含纤维素轻工生物质过程残渣能源化提供了技术选择建议.